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POSTHARVEST LOSSES AND EVALUATION OF THE BIOEFFICACY OF 
Chromolaena odorata AND Jatropha gossypiifolia AGAINST Sitophilus zeamais 
MOTSCH AND Tribolium castaneum HERBST IN THE AWUTU-SENYA DISTRICT 
OF THE CENTRAL REGION OF GHANA 
 
BY 
 
IRENE SEPEYA KARGBO 
(10361079) 
 
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON, IN 
PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF MASTER 
OF PHILOSOPHY DEGREE IN ENTOMOLOGY 
 
INSECT SCIENCE PROGRAMME* 
UNIVERSITY OF GHANA, LEGON 
JULY, 2013 
*Joint Interfaculty International Programme for the Training of Entomologists in West 
Africa. Collaborating Departments: Animal Biology and Conservation Science (Faculty of 
Science) and Crop Science (School of Agriculture, College of Agriculture and Consumer 
Sciences), University of Ghana, Legon 
 
 
 
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DECLARATION 
I, IRENE SEPEYA KARGBO, do hereby declare that except for the references cited which have 
been duly acknowledged, this thesis is the result of my own research undertaken by me towards 
the award of Master of Philosophy degree in Entomology in African Regional Postgraduate 
Programme in Insect Science (ARPPIS), University of Ghana, Legon. This work has never been 
presented anywhere either in part, or in whole for the award of any degree. 
………………………………………………………. 
IRENE SEPEYA KARGBO 
(CANDIDATE) 
………………………………………                               .………………………………………… 
PROFESSOR DANIEL OBENG-OFORI                  PROFESSOR EBENEZER O. OWUSU 
              (SUPERVISOR)               (SUPERVISOR)   
                                      
 
….................................................................................. 
DR. VINCENT YAO EZIAH 
(SUPERVISOR) 
    
 
 
…………………………………………………………. 
DR. ROSINA KYEREMATEN 
(ARPPIS COORDINATOR)  
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ABSTRACT 
A survey was conducted within five maize farming communities namely: Ahentia, Bontrase, 
Chochoe, Kroebogyir and Kwai-Blagu in the Awutu-Senya District in the Central Region of 
Ghana to determine the perception of maize farmers with respect to grain losses in their storage 
structures. The two major insect pests of maize encountered in the district namely Sitophilus 
zeamais Motschulsky and Tribolium castaneum Herbst were used as test insects.  Bio-efficacies 
of diethyl-ether and methanol extracts of dried Jatropha gossypiifolia L. and Chromolaena 
odorata (L.) King and Robinson leaf and bark were evaluated as bio-insecticidal agents against 
the beetles using topical application and grain treatments under laboratory conditions. A 
conventional grain storage insecticide, pirimiphos-methyl (Actellic 25 EC) was used as a 
reference product. The assays were run in complete randomized design with three replications. 
The effect of the methanol and diethyl-ether leaf and bark extracts of the two plant species at 
different concentrations (20%, 50% and 100%) on the adult insects in grain treatment was also 
determined in the laboratory. The survey showed that about 80%, 12% and 8% of farmers 
reported insects, rodents and moulds, respectively, to cause damage to maize grains stored in 
these traditional storage structures. Sitophilus zeamais was the major insect pest identified by 
farmers and ranked as the most destructive, followed by T. castaneum. Most of the farmers (52%) 
applied either chemicals such as actellic or phostoxin or dried the maize frequently (28%) to 
control maize grains against pest infestation. Other post-harvest practices such as dehusking and 
shelling (8%) to prevent further damage were also commonly used by farmers. The laboratory 
assays of the two plants‘ parts showed varying levels of toxicity to the two insects, but 
comparatively the leaf extracts were more toxic than the bark extracts against S. zeamais and T. 
castaneum. Both plant products were not as effective as Actellic 25 EC.  The methanolic leaf 
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extracts of C. odorata and J. gossypiifolia were effective at 20% and significantly increased the 
mortality of T. castaneum and S. zeamais to 66.1% and 77.7%, respectively. Percentage mortality 
of the insects was significantly increased at higher concentration of the extracts. The highest 
mortality of 90% was recorded at 4 ml/L of Actellic for S. zeamais. A repellency of 83.3% was 
recorded for 20% diethyl-ether leaf extract of J. gossypiifolia against both insects compared to 
100% repellency produced by Actellic against T. castaneum. The methanolic leaf extracts of C. 
odorata, diethyl-ether leaf extracts of J. gossypiifolia at 20% and reference product completely 
inhibited the development of both insects (0.0%) as no adults emerged in these treatments. Grains 
treated with the plant extracts significantly reduced damage caused by S. zeamais and T. 
castaneum compared with the untreated grains. The current findings showed that extracts of C. 
odorata and J. gossypiifolia could potentially be used in IPM programmes as environmentally 
friendly products for the management of stored-product beetles and may be exploited for the 
development of botanical insecticides for grain protection. This would, however, require further 
field studies to establish levels that would produce consistent and acceptable results. 
 
 
 
 
 
 
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DEDICATION 
This thesis is dedicated to my parents Mr. & Mrs. Alfred C. Kargbo, Sr., for their prayers, 
encouragement and support, in all my endeavours; especially my daddy who so lovingly and 
unselfishly cared for my kids during the course of this study, my daughters-Angel, Nenneh and 
Uche for their  patient love, and my siblings who always wished the best for me.  
 
 
 
 
 
 
 
 
 
 
 
 
  
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ACKNOWLEDGEMENT 
I am thankful to the Almighty God for his grace and gifts of wisdom and good health throughout 
this research. I am infinitely indebted to my supervisors Prof. Daniel Obeng-Ofori, Prof. Ebenezer 
Oduro Owusu and Dr. Vincent Yao Eziah for their wise advice, motivation and for expertly 
conceiving this research and diligently guiding its process to the end despite their many other 
academic and professional commitments; special thanks to all the lecturers and Mr. Davis of 
ARPPIS for their meticulous training which prepared me for this research. 
I would like to express my profound gratitude to Mr. Benjamin Wilson, Director of MoFA, 
Awutu-Senya District, O. Joseph and Mr. Sam for their help in the selection of extension officers, 
extension officers Dennis, Amelia, and Misters Okine, Manford and Dagba for their help in the 
selection of farmers, and all the farmers who participated in this this project with interest and 
enthusiasm. Special thanks to Mr. Asante for helping me with the analysis of data, and Mr. K. 
Matey for his guidance in the experimental work. 
I would also like to appreciate Mr. Rufus Karmorh of Firestone for his encouragement and all my 
colleagues of the Firestone-Liberia Senior High School for their prayers and best wishes. May 
God bless you all. 
To my course mates: Elizabeth, Sheila, Gloria, Denis, James, Friday, Chernor and Jallow, without 
you, pursuing a second degree would not have been competitive and fun.  
My studies at the African Regional Postgraduate Programme in Insect Science (ARPPIS), 
University of Ghana, would not have been possible without the sponsorship of the Government of 
Liberia through the Ministry of Agriculture. This research was funded by a student grant from 
African Development Bank. 
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TABLE OF CONTENTS 
 
DECLARATION ............................................................................................................................................ ii 
ABSTRACT ................................................................................................................................................... iii 
DEDICATION ................................................................................................................................................ v 
ACKNOWLEDGEMENT ............................................................................................................................. vi 
TABLE OF CONTENTS .............................................................................................................................. vii 
LIST OF TABLES……………………………………………………………………………..…..xi 
LIST OF FIGURES ..................................................................................................................................... xiii 
LIST OF PLATES ....................................................................................................................................... xiv 
LIST OF ABBREVIATIONS ...................................................................................................................... xvi 
CHAPTER ONE ............................................................................................................................................. 1 
1.0 GENERAL INTRODUCTION ................................................................................................................. 1 
1.1 Introduction ........................................................................................................................................... 1 
1.2 Justification ........................................................................................................................................... 3 
1.3 Objectives ............................................................................................................................................. 4 
CHAPTER TWO ............................................................................................................................................ 6 
2.0 LITERATURE REVIEW ......................................................................................................................... 6 
2.1 Origin and uses of maize ....................................................................................................................... 6 
2.2 Maize production in Ghana and its contribution to the economy ......................................................... 6 
2.3 Classification of grain quality ............................................................................................................... 9 
2.3.1 Grain losses .................................................................................................................................. 10 
2.3.2 Estimates of post-harvest losses ................................................................................................... 12 
2.3.3 Factors and causes of grain loss ................................................................................................... 13 
2.4 Insect pests of stored maize ................................................................................................................ 14 
2.4.1 Damage caused by insect pests of stored maize ........................................................................... 15 
2.4.2 Storage losses caused by insect pests of maize ............................................................................ 17 
2.5 Biology and behaviour of the maize weevil, Sitophilus zeamais ........................................................ 18 
2.6 Biology and behaviour of the red rusty flour beetle, Tribolium castaneum ....................................... 20 
2.7 Maize handling and storage ................................................................................................................ 21 
2.8 Maize storage methods and structures ................................................................................................ 22 
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2.9 Description of traditional storage structures ....................................................................................... 24 
2.9.1 Temporary grain storage methods ................................................................................................ 24 
2.9.2 Long-term grain storage methods ................................................................................................ 25 
2.10 Assessment of post-harvest storage losses ........................................................................................ 31 
2.11 Methods of assessing grain losses in storage .................................................................................... 32 
2.12 Detection of hidden infestation ......................................................................................................... 39 
2.13 Control of stored product insect pests ............................................................................................... 42 
2.13.1 Use of traditional methods ......................................................................................................... 43 
2.13.2 Use of physical control .............................................................................................................. 43 
2.13.3 Use of chemical control ............................................................................................................. 44 
2.13.4 Use of biological control ............................................................................................................ 48 
2.13.5 Use of phytochemicals/botanicals .............................................................................................. 49 
2.13.6 Use of plant products in stored product protection .................................................................... 51 
2.14   The Bellyache bush, Jatropha gossypiifolia L. ............................................................................... 52 
2.14.1 Taxonomy, distribution and ecology ......................................................................................... 52 
2.14.2 Uses ............................................................................................................................................ 54 
2.15 The Siam weed, Chromolaena odorata (L) King and Robinson ...................................................... 57 
2.15.1 Taxonomy, distribution and ecology ......................................................................................... 57 
2.15.2 Uses ............................................................................................................................................ 60 
2.16 Pirimiphos-methyl (Actellic) ............................................................................................................ 62 
2.16 .1 Structural Formula of Pirimiphos-methyl (C11H20N3O3PS) ...................................................... 62 
2.16.2 Identity and Properties of Pirimiphos-methyl ............................................................................ 62 
2.16.3 Uses ............................................................................................................................................ 63 
2.16.3.1 Use pattern .............................................................................................................................. 65 
CHAPTER THREE ...................................................................................................................................... 67 
3.0 MATERIALS AND METHODS ............................................................................................................ 67 
3.1 The study area ..................................................................................................................................... 67 
3.2 The survey ........................................................................................................................................... 68 
3.3 Determination of baseline data ........................................................................................................... 70 
3.4 Determination of grain moisture content ............................................................................................ 70 
3.5 Chemical used as standard insecticide check ...................................................................................... 71 
3.6 Assessment of the bio-efficacy of C. odorata and J. gossypiifolia against major insects    
encountered during the survey .................................................................................................................. 71 
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3.6.1 Culturing of insects for laboratory bioassays ............................................................................... 71 
3.7 Plant materials used for the assays ...................................................................................................... 72 
3.8 Preparation of extracts ........................................................................................................................ 73 
3.9 Contact toxicity by topical application ............................................................................................... 74 
3.10 Repellency test .................................................................................................................................. 75 
3.11 Toxicity of extracts on adult insects in treated grains ....................................................................... 76 
3.12 Oviposition test ................................................................................................................................. 76 
3.13 Effect of extracts on immature stages of S. zeamais and T. castaneum ............................................ 78 
3.14 Grain dissection to detect dead immatures ....................................................................................... 79 
3.15 Assessment of grain weight loss ....................................................................................................... 80 
3.16 Data analysis ..................................................................................................................................... 81 
CHAPTER FOUR ......................................................................................................................................... 82 
4.0 RESULTS ......................................................................................................................................... 82 
4.1 Farmers‘ knowledge and perception concerning postharvest losses in maize .................................... 82 
4.1.1 General background of maize farmers in the Awutu-Senya District ........................................ 82 
4.2 Production, harvesting and postharvest practices ............................................................................... 84 
4.2.1 Maize varieties grown by farmers ................................................................................................ 84 
4.2.2 Varieties of maize grains stored………………………………………………………………...85 
4.2.3 Training of farmers by AEOs............................................................................................................... 86 
4.2.4 Harvesting and storage ................................................................................................................. 87 
4.2.5 Postharvest practices before storage ............................................................................................ 88 
4.3 Storage structures ................................................................................................................................ 90 
4.3.1 Characteristics of the three storage structures .............................................................................. 93 
4.3.2 Types of materials used for construction of storage structures .................................................... 94 
4.3.3 Age of grain stores ....................................................................................................................... 94 
4.3.4 Maize storage efficiency .................................................................................................................. 95 
4.5 Storage losses ...................................................................................................................................... 95 
4.5.1 Farmers‘ assessment of storage losses ......................................................................................... 95 
4.5.2 Visual observation of storage losses ............................................................................................ 96 
4.6 Pests control measures by farmers ...................................................................................................... 98 
4.7 Contact toxicity of extracts on insects by topical application ............................................................. 99 
4.8 Repellency assays ............................................................................................................................. 100 
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4.9 Toxicity of extracts on adult insects in treated grains ....................................................................... 102 
4.10 Detection of hidden infestation ....................................................................................................... 105 
4.10.1 Oviposition ............................................................................................................................... 106 
4.11 Effect of extracts on immature stages of T. castaneum and S. zeamais .......................................... 107 
4.11.1 Effect of extracts on eggs ......................................................................................................... 107 
4.11.2 Effect of extracts on larvae ...................................................................................................... 109 
4.11.3 Effect of extracts on pupae ....................................................................................................... 110 
4.12 Grain dissection to detect dead immatures ..................................................................................... 111 
4.13 Damage assessment ........................................................................................................................ 113 
CHAPTER FIVE ........................................................................................................................................ 115 
5.0 DISCUSSION ....................................................................................................................................... 115 
5.1 Socio-economic characteristics of farmers ....................................................................................... 115 
5.2 Production, harvesting and postharvest practices ............................................................................. 115 
5.2.1 Area under maize cultivation ..................................................................................................... 116 
5.3 Varieties of maize stored and farmers‘ knowledge on modern farm practices ................................. 117 
5.3.1 Types of materials used for construction of storage structures .................................................. 118 
5.3.2 Maize storage efficiency ............................................................................................................ 119 
5.4 Maize losses incurred by farmers...................................................................................................... 121 
5.5 Pests control measures by farmers .................................................................................................... 122 
5.6 Contact toxicity of extracts on insects by topical application ........................................................... 122 
5.7 Repellent effect of extracts on insects ............................................................................................... 123 
5.8 Toxicity of extracts to adult insects in treated grains ........................................................................ 124 
5.9 Oviposition test ................................................................................................................................. 124 
5.10 Effect of extracts on immature stages of T. castaneum and S. zeamais .......................................... 125 
5.11 Damage assessment ........................................................................................................................ 126 
CHAPTER SIX ........................................................................................................................................... 128 
6.0 CONCLUSION AND RECOMMENDATIONS .................................................................................. 128 
6.1 Conclusion ........................................................................................................................................ 128 
6.2 Recommendations ............................................................................................................................. 130 
REFERENCES ........................................................................................................................................... 131 
APPENDICES …………………………………………………………………………………………….166 
 
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LIST OF TABLES 
Table                                       
2.1     Quantity of maize produced in the different regions of Ghana from 2002-2010  
           (in Metric Tonnes)                                                                            8 
2.2      Total area planted and quality of maize produced in Ghana (2006-2010)                  9 
2.3 Common organophosphorous insecticides used for stored product pest control          47 
2.4  Common pyrethroids insecticides used for stored product pest control                         47 
2.5 Combined contact insecticides commonly used against mixed insect infestation 
 in storage                                                                  48 
2.6 Plant species adopted by the Ministry of Food and Agriculture of Ghana to be  
used by farmers for stored product protection in Ghana              51 
4.1 Farmers‘ farming experience in the Awutu-Senya District                                   84 
4.2 Visit by AEOs and farm training                 86 
4.3 Farmers‘ time of harvesting                  87 
4.4       Nature of stored grain                                                                         88                            
4.5 Maize kept for seed                              88 
4.6       Reasons for storing surplus maize in the district                          89 
4.7       Reasons for storing maize                  89 
4.8       Reasons for storing low quantity of maize in the district                         90 
4.9       Types of storage structures commonly used by maize farmers in the district           92 
4.10     Age of farmers‘ stores in the district                 94 
4.11 Storage efficiency based on grain loss and storage length              95 
4.12 Pest control measures used on stored maize                                      98 
 
 
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4.13     Contact toxicity of 20 % methanol and diethyl-ether extracts of C. odorata  
            and J. gossypiifolia by topical application on T. castaneum and S. zeamais       100 
4.14    Mean % repellency of 20% of methanol and diethyl-ether extracts of C. odorata  
            and J. gossypiifolia against T. castaneum and S. zeamais         101 
4.15    Mean % mortality of T. castaneum and S. zeamais exposed to grains treated  
           with 20% extracts of C. odorata and J. gossypiifolia after 96 hours        103 
4.16    Mean % mortality of T. castaneum and S. zeamais exposed to grains treated 
           with 50% extracts of C. odorata and J. gossypiifolia after 96 hours        104 
4.17    Mean % mortality of T. castaneum and S. zeamais exposed to grains treated  
           with 100% extracts of C. odorata and J. gossypiifolia after 96 hours          105 
4.18    Mean total number of eggs laid by S. zeamais and T. castaneum per 20 grains using the  
            acid fuschin solution egg staining technique            107 
4.19   Mean adult emergence (%) of T. castaneum and S. zeamais after treating eggs with 
         
           20% extracts of C. odorata and J. gossypiifolia                      108 
 
4.20   Mean adult emergence (%) of T. castaneum and S. zeamais after treating larvae with  
          20% extracts of C. odorata and J. gossypiifolia                      109 
4.21   Mean adult emergence (%) of T. castaneum and S. zeamais after treating pupae with  
         20% extracts of C. odorata and J. gossypiifolia                      110 
4.22   Mean number of larvae and pupae of S. zeamais and T. castaneum dissected from  
           stored grains                                                                                  112 
4.23 Mean % weight loss caused by S. zeamais and T. castaneum on grains stored  
         with 20% extracts of C. odorata and J. gossypiifolia                                                       114 
  
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LIST OF FIGURES 
Figure                                       
3.1  A map of Awutu-Senya District showing sampled communities      69 
4.1  Gender of maize farmers in Awutu-Senya District        82              
4.2  Age of maize farmers in the Awutu-Senya District        83 
4.3  Educational level of maize farmers in the Awutu-Senya District       83                
4.4 Varieties of maize grown by the farmers in the district       85 
4.5 Maize varieties stored by the farmers in the Awutu-Senya District      87 
4.6 Causes of losses to maize during storage         96 
 
 
 
 
 
 
 
 
 
 
  
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LIST OF PLATES 
 
Plate           
2.1 Adult S. zeamais          19 
2.2 Adult T. castaneum          20 
2.3 Traditional Ewe barn with polythene cover        29                                                                                       
2.4 Maize cobs stored in roof space of house (Aerial storage)     29 
2.5 Storage platform (open)         29 
2.6 Traditional crib             29 
2.7 Thatched structure (Ava)          30 
2.8 Woven basket store          30 
2.9 Mud storage structure         30 
2.10 Ground/earthenware pot         30 
2.11 Bags stored on dunnage            31                 
2.12 Opening of underground pit store         31 
2.13 Older leaves with seeds and flowers of J. gossypiifolia       54  
2.14 Immature leaves of flowers of J. gossypiifolia        54 
2.15    Leaves, flowers and stem of C. odorata        60 
3.1      S. zeamais and T. castaneum culture       72 
3.2     Leaves and bark of plants being dried in the screenhouse  73 
3.3     Stuart Scientific Flask Shaker shaking plant materials mixed with solvents   74 
3.4     Rotary evaporator             74 
3.5     Insects being tested for repellence against plant extracts     76 
3.6     Grains covered with acid-fuchsin solution       77 
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3.7     Grains examined to detect the presence of egg plugs      78 
3.8     Extracts being tested on immature stages of S. zeamais and T. castaneum   79 
4.1     Obaatanpa (hybrid)                                                  85 
4.2     Abasa (local)          85 
4.3     Mixed maize (Akpossoi)         86 
4.4     Room storage           90 
4.5    Traditional crib           91 
4.6    Traditional Ewe barn with polythene cover       91 
4.7    Arrangement of maize cobs in storage                   92 
4.8    Maize weevil, Sitophilus zeamais (Coleoptera: Curculionidae)   97 
4.9    Red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae)    97 
4.10 The larger grain borer, Prostephanus truncatus (Coleoptera: Bostrichidae)   97 
4.11   Lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)   97 
4.12   Angoumois grain moth, Sitotroga cerealella (Lepidoptera: Gelechiidae)   98 
 
 
                             
 
 
 
 
 
 
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LIST OF ABBREVIATIONS 
 
AEO …………………………………………………Agricultural Extension Officers 
a.i …………………………………………………….Active ingredient 
BCFM ………………………………………………..Broken Corn and Foreign material (USDA) 
CFP…………………………………………………..Brazilian Financing Commission 
°C…………………………………………………….Degree Celsius 
cm…………………………………………………….centimeters 
CO2…………………………………………………. carbondioxide 
COG………………………………………………….cost of grain 
E.g……………………………………………………example 
FAO………………………………………………….Food and Agriculture Organization 
Fig……………………………………………………Figure 
FW…………………………………………………...final weight 
g……………………………………………………...grams 
GDP…………………………………………………Gross Domestic Product 
GH¢…………………………………………………Ghana cedis 
GISD………………………………………………..Global Invasive Species Database 
GLSS………………………………………………..Ghana Living Standard Survey 
ha…………………………………………………….hectares 
HGCA ………………………………………………Home Grown Cereal Association 
IITA…………………………………………………International Institute of Tropical Agriculture 
IPCS INCHEM……………………………………..International Programme on Chemical Safety 
IPM………………………………………………….Integrated Pest Management 
ISSER ………………………………………………Institute of Statistical Social and Economic   
                                                                                    Research 
kg…………………………………………………....kilograms 
LSD…………………………………………………Least Significant Difference 
m…………………………………………………….meter 
MC…………………………………………………..Moisture content 
ml…………………………………………………....millimeter 
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MoFA………………………………………………Ministry of Food and Agriculture 
MT………………………………………………….metric tonnes 
OPs…………………………………………………Organophosphates 
ppm………………………………………………....parts per million 
rpm………………………………………………….revolutions per minute 
SPSS………………………………………………..Statistical Package for Social Sciences 
spp………………………………………………….species 
SRID……………………………………………….Statistics, Research and Information  
                                                                                  Directorate of MoFA 
SVW……………………………………………….Standard Volume Weight 
TROPICOS………………………………………..Botanical Garden Information System 
TGM……………………………………………….Thousand Grain Mass 
TND……………………………………………….Total number of destroyed and missing grains 
UW………………………………………………...undamaged weight 
   
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CHAPTER ONE 
1.0 GENERAL INTRODUCTION 
1.1 Introduction 
Grains constitute the most important staple food for the growing population in most parts of the 
world and are usually stored to provide food reserve and seeds for planting (Niber, 1994). Maize 
is a very important crop of the world after wheat and rice (Purseglove, 1992). 
Maize (Zea mays) originated in America, and is now the principal cereal crop in the tropics and 
sub-tropics (FAO, 1992). In Ghana, maize is the largest staple crop and is the mainstay of the 
diet of the majority of Ghanaians, because it is the base for several traditional food preparations 
(such as banku, kenkey, tuozafi) (Morris et al., 1999). Additionally, it represents the second 
largest commodity crop in the country, after cocoa (ISSER, 2012). Maize is also the main 
component for poultry and livestock feed (Asiedu et al., 2002). 
Maize accounts for 50 – 60% of the total cereal production in Ghana (Egyir, 2003; ISSER, 
2012). The total average annual maize production in Ghana between 2007 and 2012 was 1.5 
million MT (MoFA, 2012), which indicates that maize supply in Ghana has steadily been 
increasing over the past few years. It is estimated that Ghana is about 99% self-sufficient in 
domestic maize production, therefore proper storage practices should be done in order to reduce 
postharvest losses to major storage insect pests which has been recognized as an increasingly 
important constraint to food security.  
Many factors including biotic (insect pests, mites, rodents and micro-organisms) and abiotic 
(high moisture content, relative humidity and temperature) account for the post-harvest losses of 
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maize both in the field and storage and are responsible for the decline in quality, nutrition and 
germination potential  in storage (Forsyth, 1962; Devereau et al., 2002).  
Stored maize is attacked by 20 different species of insect pests (Mould, 1973; Ayertey, 1979). 
Some of the major insect pests of stored maize are Sitophilus zeamais Motsch (Coleoptera: 
Curculionidae), Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) and Prostephanus 
truncatus Horn (Coleoptera: Bostrichidae). In Africa the estimates of maize grain losses in 
storage vary but are known to be in the range of 20–30% (Markham et al., 1994; Van Gastel et 
al., 1999; Lamptey, 2000; Nyanteng and Asuming – Bempong, 2003; Egyir, 2003). In Ghana, 
there are reports of losses averaging 30% or more of grain dry weight in maize stored on farm 
due to infestation by Tribolium castaneum (Herbst), Sitophilus zeamais (Motsch) and Sitotroga 
cerealella (Olivier) (IITA, 1995; Egyir et al., 2008); and out of an estimated total annual harvest 
of 250,000-300,000 tonnes of maize about 20-25% is lost to S. zeamais alone (Ayertey, 1982; 
Obeng-Ofori and Amiteye, 2005). Such losses lower both the incomes and standard of living of 
farmers and also lead to wastage of a large proportion of the contribution to the nation‘s food 
supply and can pose a serious threat to the nation‘s food security (Asiedu and Van Gastel, 2001; 
FAO, 2004). Apart from the actual nutrient losses, kernels damaged by insects may be 
contaminated with dangerous levels of aflatoxins (IITA, 1995). Additionally, there is 
contamination by dead beetles, pupae and larval cocoons, some of which contain highly 
dangerous substances (IITA, 1995). 
Storage losses may be the major cause of maize price variability in Ghana. Agricultural produce 
either of plant or animal origin, durable or perishable begins to deteriorate as soon as they are 
harvested. This deterioration may commence within few minutes after harvest resulting in partial 
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or complete loss (Boxall et al., 2002). It may also take place very slowly making the crop retain 
some essential quality for months (Setamou et al., 1998).  
Currently, insect control in stored food products relies heavily on the use of fumigants and 
residual chemical insecticides. These synthetic insecticides have made a tremendous impact over 
the years in stored product protection. However, misuse of these chemicals has promoted faster 
evolution of resistant forms of pests, destroyed natural enemies, turned formerly innocuous 
species into pests, harmed other non-target species and contaminated food (Obeng-Ofori et al., 
1997). These concerns have stimulated the search for cheap, easily biodegradable and readily 
available natural products for stored product protection (Owusu, 2001; Obeng-Ofori, 2007). The 
use of locally available plant materials to protect stored products against pest damage is a 
common practice in traditional farm storage systems in most developing countries (Poswal and 
Akpa 1991; Boeke et al., 2004). A bulk of information is available on the effectiveness of 
insecticidal plants to control storage pests (Obeng-Ofori and Coaker, 1990; Owusu, 2001; Owusu 
et al., 2008; Boateng and Kusi, 2008; Udo et al., 2009). 
Jatropha gossypiifolia and Chromolaena odorata are plants with medicinal value that have long 
been known to contain some insecticidal properties (Weaver et al., 1995; CIAT, 2001; Talukder, 
2006).  
 
1.2 Justification 
The study sought to assess the postharvest losses in some selected traditional maize grain storage 
structures in the Awutu-Senya District of Ghana and to evaluate the bio-efficacy of C. odorata 
and J. gossypiifolia for the control of S. zeamais and T. castaneum in stored maize.  
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This is because effective storage stimulates both production and consumption of grains. Despite 
the widespread and continuous use of traditional storage practices by small scale farmers in the 
Awutu-Senya District, no quantitative information on maize grain losses is available. Also based 
on the fact that information of post-harvest losses is about 20 years out of date, there‘s a need to 
assess the losses in these selected storage structures to update the quantitative information of 
maize grain losses that lower both the incomes and standard of living of farmers and can pose a 
serious threat to the nation‘s food security (Asiedu and Van Gastel, 2001; FAO, 2004). 
Considering the importance of maize in providing daily calorie needs and an ingredient for 
poultry and livestock feed, protecting maize from stored product pests is of utmost importance.      
Therefore, there is need to determine the causes, types and level of losses of grains that occur 
during storage. This will help make suggestions that will lead to the effective and efficient 
storage of grains in the selected storage structures in the Awutu-Senya District. Such information 
is essential to increase the overall quantity and quality standards of maize grain, income and 
standard of living of farmers. Furthermore, the study would add to the body of knowledge on 
botanical insecticides that are environmentally safe and friendly to control storage pests making 
food available to man, his livestock and the industries, and thus providing gainful employment.  
1.3 Objectives 
The main objective of the study was to assess storage losses in traditional storage structures in 
the Awutu-Senya District of Ghana and to evaluate the bio-efficacy of extracts of J. gossypiifolia 
and C. odorata against S. zeamais and T. castaneum in stored maize. The specific objectives 
were: 
I. To survey and determine the causes and types of grain losses that occurs in the different      
traditional storage structures.  
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II. To identify the most potent part(s) of C. odorata and J. gossypiifolia against S. zeamais and T. 
castaneum infesting maize using Pirimiphos-methyl (Actellic) as a reference.   
III. To determine the toxicities and repellencies of the methanol and diethyl-ether extracts of the 
most potent plant parts against S. zeamais and T. castaneum. 
IV. To determine the effect of these extracts on the emergence of adult S. zeamais and T. 
castaneum in treated grains.  
 V. To assess the effect of these extracts on grain damage by adult S. zeamais and T. castaneum 
that occurs in the different traditional storage structures. 
 
 
 
 
 
 
 
 
 
 
  
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CHAPTER TWO 
2.0 LITERATURE REVIEW 
2.1 Origin and uses of maize 
Maize is a member of the grass family, Gramineae, and an important grain crop in the world 
after wheat and rice (Purseglove, 1992). Maize (Zea mays) originated in America, and is now the 
principal cereal crop in the tropics and sub-tropics (FAO, 1992). Maize is grown on every 
continent and in many countries and has almost replaced cereals such as sorghum and millet 
(FAO, 1992). It is an important crop in the economy of Ghana, and is grown by the vast majority 
of rural households in all parts of the country, except for the Sudan savannah zone of the far 
north, and it is a leading staple in the Southern Central, Volta and Northern Regions (Morris et 
al., 1999). Maize is prepared and consumed in many ways depending on region or ethnic group. 
For example in Ghana, kenkey, tuozaafi and banku, and Nigeria, meals such as eba and eko are 
prepared from maize (Morris et al., 1999). In some parts of Africa, maize is mainly consumed as 
thick porridge (ugali in East Africa and sadza in Zimbabwe). A thin porridge (uji in East Africa, 
ogi in Nigeria, koko in Ghana) is also commonly eaten, especially as a weaning food (Morris et 
al., 1999). 
2.2 Maize production in Ghana and its contribution to the economy 
Agriculture continues to be the bedrock of Ghana‘s economy accounting for more than 48% of 
GDP in 2011, at a growth rate of 13. 5% and contributed to about 50% of foreign exchange 
earnings (GLSS, 2008; ISSER 2011). In terms of sales value, maize is an important cash crop in 
Ghana.  
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Maize is produced in all the ecological regions in Ghana, namely the Forest, Coastal Savannah, 
Forest Savannah transition, Guinea Savannah, Sudan Savannah and Sahel Savannah (Egyir, 
2003).   
According to the Ghana Living Standard Survey (GLSS, 2000), climatically, there are three 
ecological zones, the northern savannah, coastal savannah and forest zones. In the forest zone the 
climate is dominated most of year by moist air and conventional rainfall is frequent. The rainfall 
is usually between 1000 and 2000 cm per annum, falling in two seasons with only a short dry 
season of reduced rainfall between them. In Southern Ghana, where this condition is prevalent, 
two cropping seasons of maize are possible. The savannah areas may have two short rainy 
seasons and a pronounced intervening dry season, as in the coastal areas, or a medium, lengthy 
rainy season and a long dry season as found in most parts of Northern Ghana. 
Although, maize production cuts across all the 10 regions of Ghana, the Eastern, Ashanti, 
Central, Brong-Ahafo and the Northern Regions are the five major growing areas (SRID of 
MOFA, 2011).  
Maize is produced mostly by small-scale farmers using simple hand tools such as hoe and 
cutlass. Very few commercial maize farms are in operation presently in Ghana (e.g.Ejura Farms). 
The level of production on individual farms is very low, hence the need to minimize postharvest 
losses. The common varieties cultivated in Ghana include Obaatanpa, Abasa, Okomasa, Abrotia, 
Dobidi, Abeleehi and Dodzi (Aikins et al., 2010). The harvested maize cobs in sheath are either 
stored inside the room either in loose piles, traditional barns or the crib.  
Table 2.1 shows the quantity (in metric tonnes) of maize produced from 2002-2010 in the  
10 regions of Ghana. The total area planted and quality of maize produced in Ghana from 2006 – 
2010 is also shown in Table 2.2.  
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While there is no recent reliable data for corn used in animal feed, the COG estimates that 85% 
of all corn grown in Ghana is destined for human consumption and the remaining 15% is used 
for animal feeding sector (mainly poultry) (Grain and Feed Annual Grain Report, 2011). Thus, to 
meet the increasing demands of maize, farmers may have to adopt improved production and 
handling systems. In the Central Region of Ghana, the total maize production in the years 2008, 
2009, and 2010 were 182,000, 187,383 and 195,394 MT, respectively (www.ghananation.com). 
Table 2.1: Quantity of maize produced in the different regoions of Ghana from 2002-2010  
                  (in Metric Tonnes) 
Regions  2002 2003 2004 2005 2006 2007 2008 2009 2010 
Western  86,520 86,520 159,622 72,135 73,210 75,406 77,553 75,210 74,191 
Central  247,110 247,110 159,622 164,398 166,847 176,222 182,000 187,383 195,394 
Eastern  218,900 244,000 241,621 206,467 209,542 227,505 280,806 303,400 380,505 
Gt. Accra 2,610 2,610 2,714 2,103 2,134 2,775 2,882 3,210 3,584 
Volta  58,630 58,630 53,868 47,577 48,286 49,978 72,858 78,868 93,887 
Ashanti  187,000 193,920 183,032 161,816 164,226 169,383 182,848 186,830 253,374 
Brong-Ahafo 295,680 295,680 281,267 358,259 363,595 381,435 402,688 453,816 510,172 
Northern  79,050 79,050 74,566 96,717 98,157 88,037 131,857 162,622 202,316 
Upper-West 60,710 60,710 60,801 47,422 48,128 40,104 55,223 73,610 96,018 
Upper-East 20,370 20,370 14,650 14,496 14,712 8,756 27,528 51,143 62,256 
Total  1,256,580 1,288,600 1,157,621 1,171,390 1,188,836 1,219,601 1,416,243 1,576,092 1,871,697 
Source: Statistics, Research and Information Directorate (SRID), MoFA (2002-2010) 
 
 
 
 
 
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Table 2.2: Total Area planted and quality of maize produced in Ghana (2006-2010) 
2006 2007 2008 2009 2010 
Area planted (000, ha) 
793 790 846 954 992 
Quality produced(‗000, tonnes) 
1188 1220 1470 1620 1872 
                              Source: ISSER, 2006-2011; The World Bank Group, 2011 
2.3 Classification of grain quality 
To facilitate marketing and to identify the best uses for the various types of maize produced 
throughout the world, measures of grain quality have been determined, although they may not be 
accepted by all maize - producing countries (FAO, 1992). In the United States maize is classified 
into five different grades, based on several factors (FAO, 1992). The maximum permitted 
amount of broken maize and foreign material (BCFM) varies from 2 percent for Grade 1 to 7% 
for Grade 5. Maize is also classified as yellow, white or mixed maize. Yellow maize must have 
not more than 5 percent white kernels and white maize must not have more than 2 percent yellow 
grains. The mixed class contains more than 10 percent of the other grain (Schuler et al., 1978; 
FAO, 1992).  
Moisture content of maize is an important part of its chemical composition and it is 
fundamentally important in establishing safe storage conditions (Devereau et al., 2002). Changes 
in moisture content also cause a change in overall weight of a commodity, and as products are 
often traded by weight this has obvious financial implications (Devereau et al., 2002). Although 
the moisture content of maize is not considered a quality factor, it has much influence on 
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composition, quality changes during storage and processing (Golob et al., 2004). High moisture 
content in maize with a soft texture is easily damaged in storage, while maize with low levels of 
moisture becomes brittle. The most commonly accepted moisture level for marketing purposes is 
15.5% (FAO, 1992). Density of maize (weight per unit volume) is important in storage and 
transportation since it establishes the size of container for test weight are related; the higher the 
moisture level the lower the specific density test weight and this affects milling (Devereau et al., 
2002).  
Another important quality characteristic of maize is its hardness, which influences grinding 
power requirements, dust formation, nutritional properties, processing for food products and the 
yield of products from dry and wet milling operations (FAO, 1992). Hardness of maize is 
genetically controlled, but it can be modified by both cultural practices and post-harvest handling 
conditions (FAO, 1992). Many investigators have proposed methodologies for measuring 
hardness for a number of different applications (Pomeranz et al., 1984; 1985; 1986). Maize 
varieties with a horny endosperm such as flint and popcorn types have hard kernels, while 
starchy and opaque maize varieties are soft. Some flint types are intermediate (FAO, 1992). 
2.3.1 Grain losses 
Food grain losses may be direct or indirect. A direct loss is disappearance of food by spillage, or 
consumption by insects, rodents and birds (Schuler et al., 1978). An indirect loss is the lowering 
of food quality to the point where people refuse to eat it (Mejia, 2003). Post-harvest crop losses 
occur at different stages: - from the moment when crops are harvested until they are sold at the 
market. These stages include field handling, on-farm storage, processing, packaging, 
transportation and market handling (Mejia, 2003). Post-harvest crop losses, especially in grains 
are due to insect, rodent damage and fungal infection (Adesuyi, 1982; Farrell et al., 2002).  
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Post-harvest losses in grain, in the developing countries are estimated at 25-40% of the total crop 
harvested (Salunkhe et al., 1985; Voices Newsletter, 2006). This means more than one-quarter of 
what is produced never reaches the consumer for whom it was grown, and the effort and money 
required to produce it are lost forever. Estimates of maize grain loss in storage vary but are 
known to be in the range of 20% - 30% (Lamptey, 2000; Egyir, 2003).     
Post-harvest losses can have very serious implication for farmers, consumers and the 
environment (Golob et al., 2002). Farmers‘ financial and food security can be severely affected, 
while consumers face hunger if post-harvest losses of important staple crops occur on a wide 
scale in the area where they live. Consumers also risk illness if they eat food that has been 
infected by fungi or other contaminants (Voices Newsletter, 2006). 
Losses may be qualitative or quantitative, or a combination of both, and result from the inability 
of the host to limit biological damage (Thompson, 1996). In addition, produce may be 
predisposed to further attack because points of entry for secondary insect pests and saprobic 
fungi have been created by the existing damage (Waller, 2001). Produce with surface blemishes, 
such as discoloration, blotches or signs of insect activity, may be rejected by graders or 
consumers and hence give rise to qualitative losses (Cantwell and Kader, 2006). Qualitative 
losses are particularly important in the international trade, where emphasis is placed on visual 
quality, and where even a small cosmetic defect may render the produce unsaleable (Waller, 
2001). Quantitative losses arise when stored produce is directly consumed by primary insect 
pests and rodents, or from the rapid and extensive decay caused by the action of micro-organisms 
(Wills et al., 1998).  
Attack usually begins with one or a few species, followed by invasion of a broad range of non-
specific micro-organisms or secondary insect pests (Golob et al., 2002). The feeding habits of 
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primary pests may lead to quality losses, since some insects exhibit a preference for feeding on 
the germ region of the seed, leading to a loss in nutritive value and seed viability in cereal grains 
(Farrell et al., 2002).  
2.3.2 Estimates of post-harvest losses 
Losses may occur at all stages in the post-harvest system; during transportation to the home, in 
storage and at processing, but it is very difficult to assess losses which occur at each of these 
stages (Boxall et al., 2002). The ability to accurately assess the losses during grain storage in 
different structures is essential in determining the extent of losses and protection a given 
structure can provide for the grains over a certain period. Most estimates have focused on 
measuring weight loss during storage. In Malawi, losses in stored local maize were found to be 
3% or less for maize stored up to 10 months in the Lilongwe Plain and Lower Shire Highlands 
(Golob, 1981) and similar losses have been recorded in Zambia (Adams and Harman, 1977) and 
Kenya (De Lima, 1979). Over the past 25-30 years various levels of postharvest losses, 
especially grain have been quoted as between 25-30% (Lamptey, 2000). Estimates of losses in 
Ghana have been given at one time or the other as 12% (1951), 25% (1968), 10-30% (1976) 
25.3% (1985) and 20% (1998) (Bani, 1991a & b).  
The estimated loss of maize, sorghum, millet and rice are approximately 18%, 7.5%, 6.6% and 
5.5% respectively (Egyir et al., 2008). For the cereals, most losses occur during harvesting, 
temporary processing, packaging, storage, transportation and loading. The minor season losses 
appear lower for all the cereals, except rice. Egyir et al. (2008) estimated the average losses of 
maize to be 13.95%. Most of these losses have been attributed to damage caused by insects, 
rodents, rainwater, birds, fire, moulds, and ground water (Farrell et al., 2002).  
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2.3.3 Factors and causes of grain loss  
Perishable and durable stored food may be considered to be an ecosystem (Multon, 1988; Sinha, 
1995). The interactions between the physical, climatic, chemical and biological factors within the 
ecosystem lead to changes in the quality and nutritive value of the stored product (Saucer, 1992; 
Jayas, 1995; HGCA, 1999).  
Knowledge of these factors is necessary if the quality and quantity of stored products are to be 
maintained. The physical factors which are most important during storage are temperature, 
moisture content of the crop, relative humidity of the atmosphere and concentration of 
atmospheric gases (oxygen, carbondioxide) (HGCA,1999). All living things, including the stored 
product itself, insects, mites and micro-organisms within the store are affected by these factors. 
Control of losses and maintenance of desirable quality traits depends to a great extent upon the 
measurement and control of these physical factors (HGCA, 1999). Physical factors do not exist 
in isolation. There are defined relationships between many of them, influenced by the presence 
and type of stored product. A change in one physical factor may lead to changes in another, and 
may lead to conditions which either promote or prevent spoilage (Mejia, 2003). Physical factors 
are those that directly affect the nature and appearance of the stored commodity, thereby 
determine its susceptibility to pest attack (Mejia, 2003). Climatic factors include temperature, 
humidity and moisture content. Biological factors include insects, mites, rodents and fungi. 
Many aspects of insect development and behavior are controlled by physical and environmental 
conditions of both the stored grain and the storage premises (HGCA, 1999; Mejia, 2003; Golob 
et al., 2002). Since most of these factors are quantitative, it therefore can affect insect biology in 
proportion to their intensity, while others trigger or control behavior (Saucer, 1992).  
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The magnitude of storage losses in a given instance is, therefore due to the combined effects of 
the physical and biological factors. The losses could be minimal in cool dry areas, high in cool 
damp conditions, marked in hot, dry areas and very high in hot damp climates (Golob et al., 
2002). The type of storage structures used during storage and the storage management can 
regulate the effects of these factors (Hoseney and Faubion, 1992).  
2.4 Insect pests of stored maize  
Stored produce is at risk from problems not faced by crops in the field because seeds and fruits 
are essentially dormant structures; their cells are physiological different from those of the 
growing plant (Golob et al., 2002). In addition, bulking of produce, in store or transit, gives rise 
to conditions very different from those in the field (Wheeler, 1969). A wide range of biological 
factors influence stored products. Any organic product that is not kept in a sterile manner is 
liable to be degraded by some biological agent, if it is kept long enough (Golob et al., 2002). 
Insects of the Orders Coleoptera and Lepidoptera are known to cause most damage to stored 
grains and grain products throughout the world (Fatope et al., 1995; Abate et al., 2000). These 
may occur on commodities as primary or secondary pests and the extent of damage depends on 
the stage of the development or growth of the insect. In Ghana, the most frequently encountered 
storage insect pests of cereals including maize are Sitophilus zeamais (Motsch.), Sitophilus 
oryzae (L.), Tribolium castaneum (Herbst), Callosobruchus maculatus (F.), and Prostephanus 
truncatus (Horn) (Fatope et al., 1995; Abate et al., 2000). The major moth pests include Ephestia 
cautella (Walker), Ephestia kuehniella (Zeller), Ephestia elutella (Hubner), Plodia interpunctella 
(Hubner), Corcyra cephalonica (Stainton) and Sitotroga cerealella (Olivier). In Africa, maize 
production is generally low because of the incidence of insect pests. According to FAO (1985) 
and Golob et al., (1999), the greatest loss of maize occurs during storage and is caused by four 
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agents: moulds, mites, vertebrate and insect pests. Sitophilus species have been implicated as the 
major insect pests of stored maize particularly in the tropics, and cause 50% of the total damage 
of stored maize worldwide. In Ghana, out of an estimated total harvest of 250,000-300,000 
tonnes of maize about 20% are lost to Sitophilus zeamais (Obeng-Ofori and Amiteye, 2005).  
2.4.1 Damage caused by insect pests of stored maize  
Insects that attack stored cereals and grain legumes can be described as either primary or 
secondary pests. Primary pests are those species that are capable of successfully attacking 
undamaged grain and establishing an infestation; they breed in previously undamaged solid 
grains, for example, whole cereal and pulse grains (Obeng-Ofori, 2008a). This means that they 
are capable of penetrating an undamaged seed coat and sometimes also a pod in order to feed on 
the embryo, endosperm or cotyledons of the seed. Such pests are capable of feeding on other 
solid, but non-granular commodities, for example, dried cassava (Belmain, 2002). Secondary 
pests only attack and breed in commodities that have been previously damaged by some other 
agency: a) other pests, especially primary pests, b) bad threshing, drying, handling, etc., or c) 
intentional processing of the commodity (Farrell et al., 2002).  
Sitophilus spp: They are the largest order of insects and the most largely researched (Obeng-
Ofori, 2008a). Three species are well known as pests of stored grain: Sitophilus zeamais known 
as the maize weevil, S. oryzae often called the rice weevil, and S. granaries referred to as the 
granary weevil. Adult Sitophilus feed especially on grain endosperm that has been exposed by 
breakage or by entering emergence holes. S. zeamais and S. oryzae are commonly found 
throughout the world in the tropical and subtropical regions (Longstaff, 1981; Belmain, 2002).  
o
S. zeamais and S. oryzae thrive best at warm temperatures (27 C) and in grain with not much less 
than 13% moisture content (Karma, 2000). 
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Rhyzopertha dominica (Fabricius) and P.  truncatus (Horn): Most members of the Bostrichidae 
are wood-boring insects, but two species, the lesser grain borer, R. dominica and the larger grain 
borer P. truncatus, are able to thrive in stored products such as cereals and dried cassava roots 
and are important primary pests (Obeng-Ofori, 1995; 2008). Prostephanus truncatus is a serious 
pest of maize stored on the cob and can tolerate dry conditions breeding on maize with 9% 
moisture content. Its ability to develop in grain at low moisture content may be one of the 
reasons for its success (Pederson, 1992; Belmain, 2002). It has been shown to cause about 34% 
and 70% weight loss in maize and cassava stored for 3-6 months and 4 months, respectively in 
Tanzania. In Nicaragua, weight losses of up to 40% had been recorded from maize cobs stored 
on farms for six months (Farrell et al., 2002). Adult and larvae R. dominica and P. truncatus bore 
into whole cereals and feed throughout their lives, producing large quantities of dust and frass 
containing a high proportion of undigested fragments, which can support larval development if 
sufficiently compacted (Nang‘ayo et al., 1993; Farrell et al., 2002). Prostephanus truncatus 
infest maize cobs with intact sheaths, the adult initiate their attack through the maize cobs 
gaining access to the maize by the apex of the cob. Rhyzopertha dominica and Prostephanus 
truncatus are adapted to rather higher temperatures and lower moisture contents and are 
therefore the dominant pests in hot, drier areas (HGCA, 1999).  
Tribolium castaneum: Tribolium castaneum feeds on a range of commodities, especially cereals, 
but also groundnuts, nuts, spices, coffee, cocoa, dried fruit and occasionally pulses (Obeng-
Ofori, 1991). They also feed on animal tissues, including the bodies of dead insects and attack 
and eat small or immobile stages of living insects, especially eggs and pupae. Heavy infestations 
by T. castaneum can produce disagreeable odours and flavours in commodities due to the 
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production of benzoquinones from the abdominal and thoracic defence glands of the adults 
(Leconti and Roth, 1953; Obeng-Ofori, 1991).  
Sitotroga cerealella: Sitotroga cerealella is an important primary pest of cereals and can infest 
grain in the field before harvest, especially maize and sorghum. The adults are good fliers and 
cross-infestation occurs easily. Infestations in bulk grain are generally confined to the outer, 
most exposed layers (Belmain, 2002). However, quite serious infestations can develop in cereals 
stored in bag stacks, especially if the pre-harvest infestation has been heavy. Infestations of the 
pest are most frequently encountered in farm storage since the larvae compete with those of 
Sitophilus spp (Karma, 2000).  
2.4.2 Storage losses caused by insect pests of maize  
Insect pests damage to stored grain results in major economic losses to farmers throughout the 
world (Obeng-Ofori et al., 1997). These losses are diverse and intense, and it is estimated that 
approximately one-third of the world‘s food crop is damaged or destroyed by insect pests during 
growth, harvest and storage (Jacobson, 1985). Insect pests constitute a single most important 
cause of post-harvest losses in the tropics (Prempeh, 1971), which have been estimated at 20-
30% (Dick, 1988).  
In Africa, where subsistence grain production supports majority of the population, grain losses 
caused by storage insect pests such as Sitophilus and Callosobruchus can be critical (Golob and 
Tyler, 1994). Furthermore, approximately 70% of agricultural products in Africa are stored on-
farm for periods extending from one harvest to the next and sometimes longer (Golob, 1997). 
During storage, the produce is susceptible to attack by many different pests of which insects are 
the most important. In Ghana, about 20% of annual maize and cowpea production of 750 and 
300 metric tonnes respectively are lost to insects (Owusu-Akyaw, 1991).  
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In the Sahel region, post-harvest losses are significant for bagged maize and sorghum because of 
damaged caused by insects and rodents (Alzouma, 1990). On the other hand, beetles can cause 
up to 40% loss of the region‘s legume production. Despite the fact that cereal production in 
North Africa is insufficient, this problem is compounded due to losses during post-harvest 
operations, particularly because of pest infestation in storage (Bartali, 1990). In spite of major 
technological advances in agriculture, the world food deficit situation remains serious (Anon, 
1982).  
Stored product beetles and moths can cause losses to grain in storage, either directly through 
consumption of grain, or indirectly by producing ‗hot spots,‘ causing loss of moisture, and 
thereby making grain more suitable for other pests (Longstaff, 1986; Talukder and Howse, 
1994). The ability to detect insect pests is fundamental to most recent strategies of stored product 
insect pest control (Giga and Canhao, 1992). Early warning of pest presence can be used to 
prevent damage and an efficient detection programme can lead to a reduction in losses and 
pesticide use. 
2.5 Biology and behaviour of the maize weevil, Sitophilus zeamais  
Sitophilus zeamais is found in all warm and tropical parts of the world (Hill, 1983). The weevil 
has a characteristic rostrum, which is a forward snout-like extension of the head and carries the 
mouth parts in a position that is ideal for penetrating plant tissues (Plate 2.1). The antennae are 
elbowed and eight segmented and always carried in an extended position when the insect is 
walking. There are four pale reddish-brown or orange-brown oval markings on the elytra, which 
cover the entire abdomen (Hill, 1983).  
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                                       Plate 2.1: Adult S. zeamais (Source: CABI, CPC) 
Sitophilus zeamais belongs to the Family Curculionidae, which is a large family of beetles that 
attack a range of plant tissues, with their larvae always being borers in roots, stems or seeds of 
plants. They are good fliers that are able to infest grains prior to harvesting (Caswell, 1962). 
Adults live from several months to one year and about 150 eggs can be laid throughout their 
adult life. The eggs are laid individually in small cavities chewed into grains by the female, each 
cavity is sealed and the egg protected by a gelatinous waxy secretion usually referred to as an 
o
‗egg-plug‘ produced by the female. The incubation period of the egg is about six days at 25 C 
(Howe, 1952). Temperature and moisture content are the chief factors determining the 
abundance of S. zeamais and the pest fails to develop when the moisture content of the grain is 
below 9%. Upon hatching, the larva begins to feed inside the grain, excavating a tunnel as it 
o
develops. There are four larval instars and at 25 C and 70% relative humidity, pupation takes 
place within the grains in about 25 days (Haines, 1991). The newly developed adult chews its 
way out leaving a characteristic emergence hole. Total developmental period ranges from about 
35 days under optimal conditions to over 110 days in unfavourable conditions (Haines, 1991).  
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2.6 Biology and behaviour of the red rusty flour beetle, Tribolium castaneum  
Tribolium castaneum is thought to have originated from India, but is now found throughout all 
tropical, sub-tropical and warm temperate areas of the world. The beetle is red-brown in colour 
with 11-segmented antennae, which are distinct club-like in shape (Plate 2.2).    
                                                 
Plate 2.2: Adult T. castaneum (Source: CABI, CPC) 
Tribolium castaneum lives on a wide range of commodities and also feeds as a predator on other 
insects. It has been reported as one of the most destructive secondary stored product beetle pests 
in the world (Boateng and Obeng-Ofori, 2008) attacking milled cereals and animal feeds, and 
does not multiply rapidly on dry cereal grains if these are undamaged and free of grain fragments 
or other dockage (Haines, 1991). The larvae and adults feed on a wide range of durable 
commodities and are important secondary pests of cereals having a preference for the embryo. It 
also feeds on groundnuts, nuts, spices, coffee, cocoa, dried fruit and occasionally, peas and 
beans. They can penetrate deeply into the stored commodity.  
Cannibalism and predation play a very important role in the nutrition of T. castaneum with the 
eggs and pupae often consumed by the adults. The females, which may copulate many times, lay 
their rather sticky eggs in the commodity throughout their adult lives. However, the number of 
o
eggs laid depends on the temperature. Under optimum conditions of 35 C and 75% relative 
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humidity, larvae emerge from eggs approximately three days after oviposition. The upper and 
o
lower temperature limits for development are 40 and 33 C (Haines, 1991). Under optimum 
conditions, T. castaneum has a very short life cycle which contributes to its high rate of increase, 
calculated as reaching 70 times per lunar month (Haines, 1991). However, cannibalism, 
parasitism, predation, disease and limitations of space and food curtail the high rate of increase, 
even though these density-dependent controls may be eased by emigration of the active flying 
adults. T. castaneum is a colonizing species (Dawson, 1977) and in shelled groundnuts for 
example, it is often the first stored-product pest to appear after harvesting and shelling. In late 
afternoons many individuals fly from the surfaces of infested sacks, especially when infestation 
is heavy. Their long life span and long reproductive period enable the insect to spend a 
considerable time searching for new food sources.  
2.7 Maize handling and storage  
At harvest time there is much more to eat than required, hence the need to store for future use.  
Various storage structures have been designed using different materials (natural and artificial) for 
the storage of maize in Ghana (Lamptey, 2000). Crop storage may be defined in simple terms as 
the process of taking the crop at its point of maximum palatability and nutritive values whilst 
maintaining these values without allowing them to deteriorate over an indefinite period of time 
(Lamptey, 2000).  In storage, however, the inherent qualities of the produce are seldom 
maintained and these may reduce to unacceptable levels. This is in part due to the inability of 
selected storage structures and methods to hold the commodity, keep out moisture, dry, control 
enzymatic activity and microbial growth and keep off rodents, insects and thieves (Lamptey, 
2000). Structures for the purpose of grain storage have been designed and constructed with the 
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objective of carrying out such controls. Varying degrees of success in applying the basic 
principles involved in the storage of grains have been achieved.  
Maize is stored at three main levels; these are farmer level, trader or middleman and depot or 
commercial stores. Structures used for maize storage depend on the form in which the produce is 
handled after harvest, the production level of the producer/farmer and therefore the quantity 
handled, duration of storage and intended end use of the produce (FAO, 1994a; World 
Resources, 1998; Mijinyawa, 2002; Dlamini, 2003). At the farm level, maize is stored dry on the 
cob with or without the sheath and in simple and inexpensive structures. Quantities of stored 
maize are taken from these structures periodically and hand shelled for outright sale or bagged 
for sale at a later date (Lamptey, 2000).  
2.8 Maize storage methods and structures  
Maize storage technologies are diverse among farmers and these variations have economic 
implications (Adetunji, 2007). Traditional methods of storage still predominate in most parts of 
Africa (Brice, 2002). They have been developed to suit the needs of a simple, subsistence 
farming system. However, as production systems become modernized, these storage methods are 
not able to cope with increases in production. Modern storage techniques are the best because 
they have the highest difference in gross margin and highest marginal rate of return (Adetunji, 
2007). Nyanteng (1972), Igbeka and Olumeko (1996) and Adetunji (2007) have outlined various 
traditional storage structures. These include farmhouses, cribs, barns, platforms, warehouse, 
silos, pens, yards and sheds, deep litter houses; palm fronts woven baskets, hutches and cages.  
Although a number of materials are available for construction, cost is found to be a major factor 
in the selection of materials. There is extensive use of locally sourced materials such as wood, 
natural fibers and earth for the construction of these structures. The factors which tend to reduce 
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the service life and efficiency of these facilities include rainfall, temperature and insects. The 
probability of using local storage is enhanced by farmer‘s age, semi modern structures is 
influenced by quality of maize stored while the probability of using modern storage structures is 
increased by years of experience, educational level of the farmers and quantity of maize stored 
(Adetunji, 2007). Farmers store their food crops in various traditional structures including barns, 
baskets, sacks, rooms and open sheds. Middlemen in grain trade, package grain in sacks and 
store them in their warehouses or storerooms in the market whilst sales go on (Adetunji, 2007). 
These traditional grain storage systems may provide some storage security for traditional 
farmers. However, this is normally for a limited period and losses can be high. The traditional 
storage structures provide limited protection against fungal growth, insects and rodents damage, 
especially in areas where the climate is warm and humid or where grain is stored for extended 
periods (Mejia, 2003). The increasing demand for cereals has meant that traditional farming 
systems be improved by introducing and producing high yielding varieties of grains by farmers. 
However, because of the increased production, the traditional storage system is proving 
inadequate not only in capacity, but also in protecting grain from damage, since the new varieties 
may be more susceptible to insect attack. It has therefore become necessary to improve the 
traditional small-scale, on-farm storage methods.  
A storage structure plays a single decisive role in maintaining grain quality after the grain has 
been properly conditioned and put into storage (Lamptey, 2000). The functions of a storage 
structure therefore include bearing its own and weight of the produce, creation of appropriate 
environment within itself for the safe keeping of the produce and resisting any adverse effects of 
the environment on it and also on the produce (Golob et al., 2002). The pre-storage handling of 
the grain and the structure in which the grain is stored and finally the environment within which 
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the structure is sited are all decisive factors for safe keeping of grain. The effectiveness of the 
storage structure in fulfilling its function depends on such factors as the choice of structure 
materials, the design, the constructional details and the initial status of the produce before going 
to store (Farrell et al., 2002).  
2.9 Description of traditional storage structures  
2.9.1 Temporary grain storage methods  
These methods are quite often associated with the drying of the crop, and are primarily intended 
to serve this purpose. They assume the function of storage if only the grain is kept in place 
beyond the drying period.  
The Traditional Ewe barn: This consists of radiating sticks constructed on legs of wooden stalks 
of ten to fifteen feet (Plates 2.3 and 2.7). The barn commonly referred to as Ewe barn is mainly 
used for storing maize. The maize cobs are stacked into a compact cylinder with pointed ends of 
the maize directed inwards and at an angle. This is an automatic arrangement following the shape 
of the barn. This arrangement provides some sort of drainage system for rain water falling on the 
maize. Bark of trees, raffia leaves are sometimes used to cover the stack of maize to prevent 
rainfall reaching it. Instead of being horizontal and flat, it may be conical in shape which is 
pointed at the bottom. The platforms are usually between 2 and 3 m in diameter, but some may 
be more than 6 m wide, with a maximum height of 2.5 m at the centre and 1.5 m at the periphery. 
Such structures facilitate drying because of their funnel shape (Boxall et al., 2002). This is a 
common practice in Southern Benin, Togo and Ghana.  
Aerial storage: Maize cobs, sorghum or millet panicles are sometimes tied in bundles, which are 
then suspended from tree branches, posts or tight lines, or inside the house. This precarious 
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method of storage is not suitable for very small or very large quantities and does not provide 
protection against the weather if outside, from insects, rodents or thieves (Plate 2.4).  
Open platforms: A platform essentially consists of a number of relatively straight poles laid 
horizontally on a series of upright posts with a flat top (Plate 2.5). They are mainly used to store 
unshelled maize in the forest zones. The maize cobs are stacked into a compact cylinder on top 
of the platform. The peripheral cobs are built up very carefully to form a wall, the inner cobs 
being loosely packed. The stack of cobs is girdled at intervals with ropes or twines made from 
the bark of trees to give physical support. If the platform is constructed inside a building, it may 
be raised at least 1 meter above ground level. They are usually rectangular in shape, but circular 
or polygonal platforms are common in some countries. In humid countries fires may be lit under 
elevated platforms to dry the produce and deter insects or other pests (Plate 2.5).  
Storage on the ground, or on drying floors: This method can only be provisional since the grain 
is exposed to all pests, including domestic animals, and the weather. Usually it is resorted to, 
only if the producer is compelled to attend to some other task, or lacks means for transporting the 
grain to the homestead.  
2.9.2 Long-term grain storage methods 
Traditional crib: The traditional crib differs in having a roof and wall(s). It may even be elevated 
at least one meter above ground levels allegedly, to reduce insect infestation. However, such 
cribs (especially the larger ones) are more commonly raised only 40 to 50 cm above ground 
level. These cribs are square or rectangular in shape, being constructed with open or open weave 
sides to allow extensive air flow. They may be raised up to 2 m off the ground to allow cooking 
beneath or if very large they may be located directly on the ground (Plate 2.6). Large bamboo or 
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sisal poles are often used in their construction. Cribs have sealable gaps in the wall for the 
removal of grain.  
Storage baskets: Baskets with an open weave are suitable for drying grain, e.g. sorghum heads 
and maize cobs, especially without husks. They are used in certain parts of the country for 
storage of cereals especially in the form of grains. Whereas the grains on the head are normally 
stored on a platform covered with thatch, the threshed grains are normally put in large baskets 
which are kept on the platform and covered with thatch. These are used in humid countries, 
where grain cannot be dried adequately prior to storage and needs to be kept well ventilated 
during the storage period (Plate 2.8). Under prevailing climatic conditions most plant material 
rots fairly quickly, and most cribs have to be replaced every two or three years, although bamboo 
structures may last up to 15 years, with careful maintenance (Nyanteng, 1972).  
Mud or clay silos: Mud or clay silos are usually round or cylindrical in shape, depending on the 
materials used (Plate 2.9). Rectangular – shaped bins of this type are less common, because the 
uneven pressure of the grain inside causes cracking, especially at the corners. Clay, which is the 
basic material, varies in composition from one place to another; that which is most commonly 
used for such construction work is obtained from termitaries, because the termites add a 
secretion which gives it better plasticity. To give it added strength, certain straw materials such 
as rice straw may be mixed with it to make it almost as durable as concrete. The diversity of 
materials used explains why the capacity of such silos can vary from 150 kg to 10 tonnes. Such 
grain stores are usually associated with dry climatic conditions, under which it is possible to 
reduce the moisture content of the harvested grain to a satisfactory level simply by sun-drying it.  
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The base of a solid wall bin may be made of timber (an increasingly scarce resource), earth or 
stone. The roof is usually made of thatched grass, with a generous overhang to protect the mud 
wall(s) from erosion and a side door is provided for access to the bin.  
Grounds, earthenware pots: These small capacity containers are most commonly used for storing 
seeds and pulse grain, such as cowpeas (Plate 2.10). Having a small opening, they can be made 
hermetic, by sealing the walls inside and out with a liquid clay and closing the mouth with stiff 
clay, cow dung, or a wooden bung reinforced with cloth. If the grain is dry (less than 12% 
moisture content) there is usually no problem with this kind of storage.  
Bag storage: Bag storage is a convenient way of keeping threshed grain and pulses. The need to 
thresh or shell grain may deter farmers from using bags if labour is in short supply at harvest 
time. These difficulties may be overcome by the use of shellers or threshers. Bags are usually 
made from jute or woven polypropylene, but hemp, sisal, grass and polythene sacks are also 
available. Durability of bags will depend on their quality and how they are handled. Jute sacks 
are more expensive but last longer than woven polypropylene ones, which are liable to degrade 
in sunlight. With careful use and repair, bags should last for several seasons. Bags provide the 
flexibility to store different types and different quantities of cereals and pulses. The storage 
capacity is limited only by the number of bags available and the size of the storeroom. Small 
numbers of bags may be kept in the farmer‘s house or in a separate store. This might include a 
room attached to the house, a simple pole and thatch shelter or a separate building made from 
traditional or non-traditional materials (bricks and cement).  
Bags of grain may also be stored in maize cribs. Ideally, one room or store should be kept for use 
entirely as a grain store. It is important that bags of grain are never placed directly on the floor. 
They should be stored on small storage platforms made from wooden poles (dunnage) (Plate 
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2.11). This will allow air to flow under the stacks and will stop the bags getting wet from the 
uptake of moisture from the ground. If no wood is available the bags should be stacked on a 
plastic sheet. The area around the stack should be kept clear of household items that might 
provide hiding places for insects and rodents. The stack should be well constructed to prevent 
collapse and kept away from the walls of the store if possible. In the house the stack should be 
kept away from the kitchen and fireplace. 
Underground storage: This method of storage is used in dry regions where the water table does 
not endanger the contents (Plate 2.12). Conceived for long term storage, pits vary in capacity 
(from a few hundred kilograms to 200 tonnes). Their traditional form varies from region to 
region; they are usually cylindrical, spherical or amphoric in shape, but other types are known 
(Gilman and Boxall, 1974). The entrance to the pit may be closed either by a stone sealed with 
mud or by heaping earth or sand onto a timber cover. The advantages of this method of storage 
are: few problems with insects and rodents; low cost of construction compared to that of above-
ground storage of similar capacity; hardly visible, and therefore relatively safe from thieves; no 
need for continuous inspection; ambient temperatures are relatively low and constant; the 
disadvantages are: storage conditions adversely affect viability; the grain can acquire a fermented 
smell after long storage; digging and construction are laborious; the stored grains can only be 
used for consumption; removal of the grain is laborious and can be dangerous because of the 
accumulation of carbondioxide in the pit, if it is not completely full; inspection of the grain is 
difficult; risks of penetration of water and the grains which are at the top and are in contact with 
the walls are often mouldy, even if the rest of the stock is healthy.  
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Plate 2.3: Traditional Ewe barn with                          Plate 2.4: Maize cobs stored in roof space    
polythene cover                                                                of house (Aerial storage) 
 
                         
Plate 2.5: Storage platform (open)                                  Plate 2.6: Traditional crib                                                          
 
 
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Plate 2.7: Thatched structure (Ava)                             Plate 2.8: Woven basket store 
 
                      
Plate 2.9: Mud storage structure                                     Plate 2.10: Ground/earthenware pot 
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Plate 2.11: Bags stored on                                                 Plate 2.12:  Opening of under-                                      
dunnage                                                                                                 ground pit store 
                                                                                                                                                          
 
2.10 Assessment of post-harvest storage losses  
Hodges and Farrell (2004) indicated that loss may generally be considered in terms of quantity or 
quality, each of which will have economic implications. Quantitative loss is a physical loss of 
produce that can be measured as a reduction in weight and can be measured and valued most 
readily. Qualitative loss is more difficult to assess since it is frequently based upon subjective 
judgments and is perhaps best identified through comparison with locally accepted quality 
standards. It may include the presence of contaminants, and changes in appearance, taste and 
texture that may cause the produce to be rejected by consumers. Loss of nutritional value may be 
considered as an aspect of quality loss (Bressani, 1990). Weight loss (loss of quantity) is a 
reduction in weight and it is easily detected but it may not necessarily indicate a loss of food 
material. In the case of grains, for example, it may be due to reduced moisture content (Siriacha 
et al., 1998). This is recognized and allowed for commercial transactions by a ‗shrinkage factor.‘ 
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True weight loss may result from feeding by insects, rodents and birds or from growth of micro-
organisms (Siriacha et al., 1998).  
2.11 Methods of assessing grain losses in storage 
Boxall (1986) outlined different methods for assessing grain losses and these methods are 
described below:  
The volumetric method  
This method is also known as the bulk density or the standard volume weight (SVW) method. It 
is based upon the use of equipment for measuring the bulk density of a clean, sieved sample of 
grain. At the beginning of a storage period a baseline SVW is determined from a representative 
sample of the grain put into store. Losses are recorded by following changes in the SVW on 
subsequent occasions throughout the storage period. Although the method strictly records 
changes in bulk density, the change in weight over time is taken to reflect the weight loss due to 
the damage caused by grain-boring insects. The difference in moisture content in grain samples 
collected at different times will affect the weight of grain in the standard volume container. This 
effect can be excluded by expressing all weight measurements in terms of constant moisture 
content, usually the dry weight. However, changes in moisture content also affect the volume 
and frictional properties of grain.   
There are several shortcomings in this method. An increase in moisture content will increase the 
volume of the grain and cause it to pack more loosely, leading to a decrease in the dry weight of 
a given volume. To allow for the effect of moisture on the volume of the grain it is necessary to 
calculate, by experiment, the dry weight of a standard volume of a reference sample of grain at 
different levels of moisture content. The dry weight of the grain filling the standard volume 
container for subsequent samples, taken at the prevailing moisture content, can then be related to 
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the dry weight of the reference sample at the same moisture content  by reference to a specially 
prepared graph or chart. The procedure requires a great deal of care and time and an adequately 
equipped laboratory (Adams and Schulten, 1978). Another factor affecting the weight of a 
standard volume of grain is the addition of insecticide dust. The dust adheres to the surface of the 
grain, causing an increase in the volume and a change in the frictional properties. Sieving the 
grain is unlikely to remove all the dust where insecticides have been applied; therefore, the 
volumetric method is less useful since it will tend to lead to overestimates of loss.  
Thousand grain mass method  
This method is similar to the standard volume weight method but instead of comparing weights 
of a fixed volume of grain, the weights of a fixed number of grains are compared. The thousand 
grains mass (TGM) is the mean grain weight multiplied by 1000 and corrected to a dry weight, 
and is calculated by counting and weighing the number of grains in a given sample. A baseline 
TGM is determined from a sample of grain collected in a representative manner as the grain is 
put into store. It does not involve separating damaged from undamaged grains or standardization 
of grain samples to an exact weight/volume before analysis. Subsequent measurements of the 
TGM made throughout the season are compared to the baseline value.  
The count and weigh method 
The count and weigh method provides an estimate of loss where a baseline sample cannot be 
obtained at the beginning of the storage season (Anon, 1999). It uses a sample of about 1000 
grains. The method, which is applied to a single sample, involves separating the damaged and 
undamaged grains and then counting and weighing each fraction. The data are then substituted 
into the following equation:  
Percentage weight loss =  
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Where: U = Weight of undamaged grain; D = Weight of damaged grain; Nu = Number of 
undamaged grains; Nd = Number of damaged grains.  
The method uses a single sample and it is considered unnecessary to determine the moisture 
content of the separate fractions, on the assumption that the differences are likely to be small. 
This method assumes that insects choose grains at random, which may not be true. It also does 
not account for hidden infestation, because grains containing such infestation are classed as 
undamaged (Adams and Harman, 1977). Both factors may cause misleading, or even negative, 
results at very low levels of infestation. At very high levels of infestation, misleading results 
occur because of multiple infestations in large grains such as maize, beans, and in some sorghum 
varieties. However, it is a useful, quick field method if allowance is made for the problems 
occurring at the extremes. Refinements to the technique have been addressed to solve, 
preferential attack of large or small grains, differences in moisture content between damaged and 
undamaged grains, and the presence of hidden infestation. The refinements include separating 
grains into size categories before counting and weighing (Boxall, 1986), separating superficially 
from severely attacked grains (Ratnadass et al., 1994) and making a second assessment after the 
emergence of hidden infestation (Ratnadass and Fleurat-Lessard, 1991).   
Modification of the count and weigh method 
A modification of the count and weigh method has been developed for use in the situation where 
insects completely destroy grains on maize cobs. If such missing grains are not taken into 
account when assessing losses of cob maize, the count and weigh method is likely to 
underestimate the loss (Compton et al., 1998). The method was developed to handle the larger 
grain borer, P.  truncatus, a  pest of cob-stored maize which reduces many grains to powder. It is 
recommended that a sample of about 30 maize cobs is used and that each cob is shelled 
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separately. The number of destroyed grains are counted for each cob and then summed over all 
cobs in the sample to give the total number of destroyed and missing grains (TND). The shelled 
grains from all cobs are pooled and weighed and the final weight recorded (FW). Two sub-
samples, each of about 500 grains, are extracted and the grains in each are then sorted into 
damaged and undamaged groups and counted and weighed as in the conventional method. The 
weight loss is calculated separately for the two sub samples and the average taken as the weight 
loss in the cob sample.  
The percentage weight loss is then derived from the formula below:  
 
Where: U = Weight of undamaged grain; D = Weight of damaged grain; Nu = Number of 
undamaged grains; Nd = Number of damaged grains; TND = Destroyed and Missing grains;  
FW = Final Weight 
Derivation of the equation  
The percentage weight loss in the sample defined as: The final weight (FW), is explained above. 
The undamaged weight (UW) is the estimated sample weight in the absence of destroyed and 
damaged grains and is estimated by applying the same assumptions used in the conventional 
count and weigh method (damage is equally distributed over large and small grains in the 
sample). On this basis the average weight of undamaged grains in the original cob sample will be 
equal to the average unit weight of the remaining undamaged grains in the grain sub-sample. The 
undamaged weight of the whole original cob sample is calculated as the product of the total 
number of grains estimated to be in the original sample and the unit weight of undamaged grain 
in the sub-sample. The total number of grains is the sum of the destroyed and missing grains and 
the number of grains (damaged and undamaged) in the pooled sample of shelled maize. This last 
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parameter has to be estimated and is obtained from the final sample weight divided by the 
average unit weight of all grain.  
The modified count and weigh method suffers less from systematic bias associated with 
destroyed grains than the conventional count and weigh method, which seriously underestimates 
true weight loss when grains are destroyed by insects. Hence, the modified count and weigh 
method is recommended for studies where destroyed grains are likely to be significant (Compton 
et al., 1998).  
The converted percentage damage method 
This method is suitable where a quick assessment of loss caused by grain-boring insects is 
required, without the need for equipment, for example, during a rapid field appraisal. Weight 
losses in samples of grain may be estimated by reference to the percentage of damaged grains in 
a sample. A laboratory study must be undertaken first to establish the relationship between 
damage and weight loss. A conversion factor can then be calculated and subsequently used to 
determine weight losses in other samples of the same type of grain. It is usual to determine the 
conversion factor from the results of the count and weigh method and so this technique will be 
subject to the same sources of error. The conversion factor is calculated from the following 
formula: 
Conversion factor =  
In order to avoid some of the sources of error arising from the use of the count and weigh-
technique to derive a conversion factor, it is recommended that a sample of grain with 10% or 
more damaged grains be used in the first step. This is because the count and weigh method tends 
to underestimate loss at low levels of infestation. The sample size should never be less than 500 
grains. When a subsequent sample of grain is collected, the number of insect-damaged grains in 
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a sub-sample (of not less than 500 grains) is counted and expressed as a percentage of the total 
grains present. This figure is converted to a weight loss using the predetermined conversion 
factor. They are only approximate and should be regarded as rough guides; it is preferable to 
determine conversion factors for the particular grains being studied. 
Rapid loss assessment technique based on grain damage/weight loss relationships  
A rapid field assessment technique for predicting weight loss in grains has been developed based 
on the relationship of grain damage to weight loss. Although specifically developed for cowpea 
and Bambara groundnut, the technique could be used for any grain, especially larger types such 
as maize. The technique requires the use of standard graphs relating percentage damage and 
weight loss for the commodities under study. When preparing the reference graphs, at least 10 
working samples consisting of around 500 grains are required for the preliminary laboratory 
work. The weight loss of each sample is calculated using the count and weigh method, and the 
percentage of damaged grains.  
Rapid loss assessment using visual scales 
All of the above loss assessment techniques (with the exception of the last described) are, to a 
greater or lesser extent, time-consuming, require well-trained personnel and appropriate 
equipment. These shortcomings can be overcome by using visual scales. Visual scales are used 
routinely for assessing damage in field crops and are ideal for field use, rapid to use, require 
nothing beyond reference scales (for example, photographs), and have low levels of operator bias 
(Compton et al., 1998). A technique has been developed for cob maize and dried cassava pieces 
in which sampling and scoring can take less than 15 minutes. This enables increased sampling 
and wider coverage or reduced sample error. A loss estimate is obtained on the spot, leading to a 
reduced risk of spoilage, and anomalous results can be double-checked before leaving the site. 
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After analysis, the cobs or cassava pieces can be handed back to the owner intact, avoiding the 
common problem of how to compensate farmers for any samples removed (Compton and 
Sherington, 1999). 
Difficulty in measuring losses 
Loss assessment methods tend to be slow and to require skilled field and laboratory staff. They 
are often under taken on experimental sites, making it difficult to relate the results to on-farm 
situations. There are a number of factors which tend to lead to an upward bias in the loss 
estimates. Firstly, extremes may be taken rather than averages. Ideally, the sample size and 
standard deviation should be quoted with the loss estimated to avoid this. Secondly removals 
from store over the season are not always accounted for. Where removals do occur, percentage 
losses calculated on the basis of grain remaining in store will be overestimates.  
Another source of over estimates lies in treating partial damage as a total loss, when in fact the 
damaged grain would be used by farmers for home consumption or animal feed. A fourth source 
of upward bias lies in the potential for double counting losses at different stages in the post-
harvest system. Losses at one level are related to those at other levels.  
Another difficulty in using estimates of losses to justify technical change is the problem of 
assigning to the losses a value which makes sense to the potential user of the technology. The 
most common form in which losses are expressed is as a percentage weight loss. But from the 
farmers‘ points of view what is important is the use that the grain can be put to, or the market 
price that will be received. Grain intended for sale may be consumed, or that intended for 
consumption used as animal feed. A rapid loss assessment method for estimating storage losses 
in maize and cassava has recently been developed in Togo (Compton et al., 1998).  
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2.12 Detection of hidden infestation 
Insect infestation is a common problem for stored grain. Insects can cause quantitative losses as 
they consume the kernels. A number of insect pests such as  Sitophilus, Callosobruchus, 
Rhyzopertha, Prostephanus and Sitotroga species have their immature stages (e.g. eggs, larvae, 
pupae) inside grains (FAO, 1985). Also, the appearance and organoleptic properties can be 
altered through physical damage and contamination by faeces, webbing and body parts of 
insects, respectively.  
Most of the damage and weight loss caused by insects on grain are inflicted by the primary grain 
feeders. They are capable of penetrating sound whole kernels of grain and their life cycle is 
completed entirely within the kernel in which the egg is laid or entered by the first instar larva. 
The absence of any live adults of storage insects in grain samples does not necessarily mean the 
absence of an infestation and consequently many methods have been devised to identify 
individual kernels that have become the home of the immature stages of the major insect pests. 
Therefore, due to their presence inside the grains, several detection techniques, including the 
following have been developed and applied to stored grains: 
Egg-plug staining technique (Milner et al., 1950): This is a more rapid method of detecting the 
presence of weevil infestation within grain using different staining techniques outlined below: 
Acid-fuchsin method procedure: Prepare a dye solution by adding 0.5 g acid fuchsin to a 
mixture of 50.0 ml of glacial acetic acid and 950.0 ml of distilled water. This dye solution can be 
stored for a long time and may be used repeatedly until it becomes murky.  Soak the grains to be 
treated for five minutes in warm water; drain off water and cover grain with acid-fuchsin 
solution for two minutes in warm water. If left longer, the kernels may absorb enough solution to 
make the identification of the egg plugs difficult;  pour off the dye solution (retain for future use) 
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and wash grain in tap water to remove excess dye; examine the kernels to locate the gelatinous 
egg plugs, which stains a deep cherry red. Note that the feeding punctures and mechanical 
injuries stain a lighter colour than egg plugs. The egg plugs are about the size of an ordinary pin 
prick and can readily be seen with the naked eye. The degree of internal infestation can be then 
estimated by the number of egg plugs observed. This method is not particularly accurate; it is 
time-consuming, gives no indication on the stage of insect development and is only useful for 
weevil infestation. 
This procedure was later modified to ensure more uniform staining of the egg plugs as follows: 
Prepare the stain solution following the procedure outlined above; place approximately 100 ml of 
stain solution in a 600-ml beaker; place about 25 g of grain in a tea strainer and hold it under 
warm running water until thoroughly wetted and dust and frass are washed away; allow excess 
water to drain from the grains, and then pour them into the stain solution; swirl the grain into the 
stain solution intermittently for two minutes; pour stain solution into second 600-ml beaker, 
catching the grain in the tea strainer; rinse the grain in the tea strainer under cool running water 
to remove excess stain; place the wet grain on a paper towel and examine using an illuminated 
lens to detect cherry red-stained egg plugs. 
Berberine sulphate solution: A soluble fluorescent dye (berberine sulphate) is used to stain the 
gelatinous plug secreted by female Sitophilus spp. to cover the egg cavity in the grain. Grains are 
soaked in a dilute (aqueous) solution of 20 ppm of alkaloid berberine sulphate for one minute 
followed by rinsing and examining the kernels under ultra-violet light for the greenish-yellow 
plugs. The degree of internal infestation can then be estimated by the number of egg plugs 
observed. This method is not particularly accurate; it is time-consuming, gives no indication on 
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the stage of insect development and is only useful for weevil infestation. The stained egg plugs 
will fluoresce intense yellow; feeding punctures and mechanical injuries do not fluoresce. 
Gentian violet stain (Goosens, 1949): Prepare 1% gentian violet aqueous stock solution; soak  
5 g of grain in warm water containing a wetting agent or detergent for 30 seconds; drain by 
placing the sample in a wire container, wash, and then put the wet grain on a dry paper towel for 
a few seconds; place the grain for two minutes in a staining solution that contains 10 drops of 1% 
gentian violet aqueous stock solution in 50 ml of 95% ethanol; pour off the staining solution and 
wash the grain in clear water for 20 seconds; the egg plugs are purple and very easily seen while 
the kernels are still wet or in the water. Gentian violet does not stain the endosperm. 
Grain dissection: The grain is cut vertically and examined with a microscope to reveal the 
presence of insects or parts of insects, and gives a valuable indication of the stage of 
development of an infestation relevant for any impending control method. It is best done under a 
binocular microscope and dissected with a sharp scalpel after the grains have been presoftened 
by soaking for 2 hours. 
X-ray technique: The use of X-rays, discovered in 1895 by Roentgen, was generally restricted 
to the examination of high density materials. This is described the most accurate and rapid 
method of determining internal insect infestation in samples of grain. By this method X-ray 
machines are used to take radiographs of 100 g samples of grain. These radiographs reveal the 
presence of insects‘ forms within the grain. X-ray manufacturers have now developed X-ray 
units specifically for this purpose. Several researchers at Kansas State University (Katz et al., 
1950; Milner et al., 1950; 1952) pioneered radiography in its application to agriculture, and 
developed a method for detecting hidden infestation that was marketed by the General Electric 
Company known as the "grain inspection unit". It suffered from being time-consuming 
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(approximately 15 minutes) and was not suitable for routine inspection of grain. The equipment 
is expensive but is used extensively by large milling factories. 
Carbondioxide production method: This method gives an accurate measurement of the total 
metabolic rate of the grain, and therefore cannot be specifically applied to insects. The method 
requires enclosing a quantity of grain in a gas tight bottle at 35°C for 24 hours, then drawing a 
sample of intergranular air and analyzing it for percent CO2 evolved. Dry uninfested grain is 
normally < 0.25%, between 0.3-0.5% suggests a light insect infestation (or a MC> 15%), and if 
the CO2 evolution is > 0.5%  in 24 hours, the grain is definitely unsuitable for storage without 
any further treatment (Howe and Oxley, 1944). 
2.13 Control of stored product insect pests 
Stored product insect pests population tend to increase exponentially under favourable conditions 
and availability of food, and this eventually lead to substantial losses in stored produce 
(Talukder, 1995). Throughout history, man has employed a variety of preventive and curative 
measures against pests of stored food, designed either to prevent infestation or to inhibit pests in 
their development by repelling or destroying them (Zehrer, 1994).  
Most crops become infested with insects before they are harvested, thus introducing the pests 
into storage. The basic requirement for effective pest management is a good knowledge of the 
pest (such as biology, ecology and population dynamics), its host and the environment in which 
the pest lives. These can be manipulated to make conditions unfavourable for the development of 
the pest (Talukder, 1995). In addition, a number of active pest control methods are designed to 
destroy, repel or inhibit reproduction of pests. Below are some of the control methods: 
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2.13.1 Use of traditional methods  
The use of locally available plant materials for insect pest control is a common practice in 
traditional farm storage in developing countries (Poswal and Akpa, 1991). Traditional storage 
practice throughout most African countries involves mixing grains with wood ash, laterite dust or 
sand, or suspending crop over fireplaces.  
Drying grains by exposing them to the hot sun rids produce of pests. In historical times, farmers 
used a number of substances from animal origin such as bile, urine and droppings to preserve 
and disinfest seed grains. Substances of vegetable origin have also been employed in pest control 
over several decades. The plant kingdom, being very large, offers a wealth of resources for pest 
control, the study of which had been seriously neglected at the advent of synthetic insecticides. 
Commonly, picking of pests by hand and destroying them before storage is an active mechanical 
pest control method, and is still practised in various parts of Africa. In West Africa, insect pests 
of stored cereals and legumes are mostly sorted by hand to increase marketability. Special sieves 
are also used for sifting out pests and this represents a substantial improvement over hand 
sorting. Winnowing to remove insect pests and other unwanted materials is also employed. Since 
a decade or two ago, however, more scientific investigations into the insecticidal efficacy of a 
number of different plant products have been carried out by a number of scientists at different 
research institutes worldwide. The investigations reported here are further contributions to this 
area of research.  
2.13.2 Use of physical control 
This involves manipulating the physical environment of the pest making it inimical for its growth 
and survival (Fields and Muir, 1995). By doing so, the insect population does not increase, but 
rather is reduced and eliminated. This physical attributes relate to temperature, relative humidity, 
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moisture content of grains, storage structures, forces in commodity (compression and impaction), 
irradiation and the use of inert dust. For about thousands of years now, stored product insects 
have been controlled by using physical means. In Africa, in the Neolithic times this method was 
employed in the Nile Delta by placing seeds to be stored in glass jars underground to keep them 
cool and dry (Fields and Muir, 1995). Temperature regulation is one aspect of physical control 
mostly used in stored product protection. Some insects are susceptible to high temperatures, 
while others to low temperatures. Some are also susceptible to extreme high and low 
temperatures. For example, in general, Tribolium spp. are most susceptible to high and low 
o o
temperatures of >45 C and <13 C, respectively (Kirkpatrick and Tilton, 1972; Fields and Muir, 
1995).  
Another aspect of physical control deals with controlled or modified atmospheres. Examples are 
the underground storage in Egypt and grains stored in sealed containers in most African 
countries (example Senegal). The term usually refers to the process of changing the atmosphere 
of a facility by introducing carbondioxide or nitrogen creating an environment that will not 
support the growth and development of the insect. The hermetic storage of grains is one form of 
modified atmospheres (Obeng-Ofori, 2008a).  
2.13.3 Use of chemical control  
Insecticides used in storage generally combine high toxicity of insects with low mammalian 
toxicity. Insects take up insecticides by external contact or ingestion of treated material. Most 
insecticides act by disruption of the nervous system, but mineral dusts and ashes exert a physical 
effect, damaging the exoskeleton and the insects‘ moisture control mechanism by abrasion, 
absorption or by blocking the surface (Anon, 1983).  
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According to Obeng-Ofori (2006) all insecticides used on or near stored food must meet certain 
criteria and intense regulatory review to ensure human safety. An ideal insecticide must rapidly 
kill the insect without killing non-target organisms, must be easily degradable with low residual 
activity, must be easily handled and prepared with low mammalian toxicity, must be cheap and 
readily available for the farmers to use (Boateng and Obeng-Ofori, 2008).  
Currently, the classes of contact insecticides used on or near stored products include 
organophosphates and synergized pyrethroids. These synthetic chemical insecticides are 
available in a wide variety of compounds and formulations and are applied using different 
methods including spraying, fumigation, dusting, smoking, sprinkling, fogging and evaporation 
(Billups, 1980). These insecticides may cause neurological poisoning, desiccation, suffocation or 
other complex physiological abnormalities in the target pests (Obeng-Ofori, 2008b).  
Organophosphorus insecticides act by inhibiting enzyme cholinesterase, thus preventing nerve 
impulse transmission resulting in eventual death of the insect (Walker, 1994).  
Organophosphorous (OP) compounds are effective against most storage pests, although less 
against the Bostrichidae (R. dominica (F.), P. truncatus (Horn), Dinoderus spp.) 
Organophosphorous compounds such as pirimiphos-methyl (Actellic) with effective dose as 10g 
ai/tonne of grain is a broad spectrum insecticide with remarkable knock down effect and is 
persistent for several months, and is used in the control of stored product beetles and moths. 
Other OPs used include Etrimfos, Chloropyrifosmethyl (Reldan) and Methacrifos (Damfin) 
(Obeng-Ofori, 2010) (Table 2.3). 
Pyrethroids are synthetic substitutes for pyrethrum obtained from the plant Chrysanthemum 
cinerareaefolium Trev. They are most active either for knockdown or kill and have low 
persistence (Billups, 1980). Pyrethroids are very effective against Bostrichidae, though less 
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against other species of beetles. Synthetic pyrethrins/pyrethroids used in the control of stored 
product insect pests include Bioresmethrin, Deltamethrin, Permethrin and Phenothrin (Table 
2.4). Almost all the economically important stored product insect pests throughout the world are 
resistant to most of the insecticides commonly used to protect commodities against insect 
infestation and damage (Subramanyam and Hagstrum, 1995). In view of this, two or more 
insecticides known as ―cocktails‖ are combined to control certain storage pests. For example, 
Fenitrothion (OP) + Bioresmethrin (pyrethroid) are combined to control Rhyzopertha dominica 
(F). Fenitrothion + Permithrin + Resmethrin can be mixed to control grain weevils, beetles and 
borers (Table 2.5) (Obeng-Ofori, 2008b).  
Fumigants are gases used to disinfest commodities either in stacks under gas-proof sheets or in 
sealed silos, warehouses, containers and ships (Walker, 1994). The commonly used fumigant is 
phosphine. Phosphine is highly toxic and is available as tablets, pellets, plates or sachets of 
aluminum or magnesium phosphide, which can be kept in gas tight packs. Although fumigants 
can penetrate masses of material to kill all forms of storage insects, and produce maximum effect 
within hours of application if done properly, they do not give subsequent or residual protection. 
Moreover, some insect pests such as R.  dominica (Fab.) and T.  castaneum (Herbst) are reported 
to have developed resistance to fumigants (Walker, 1994).  
Although chemical control is the fastest method of pest control, problems of insecticide residues 
which may be detrimental to the consumer, buildup of insecticide resistance by the pest, as well 
as the destruction of non-target pests are major drawbacks to its use. However, if appropriate 
application techniques are employed, these problems may be reduced (Koomson, 2003). 
 
 
 
 
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Table 2.3: Common organophosphorous insecticides used for stored product pest         
 control 
Active Ingredients  Brand Names 
Pirimiphos-methyl Actellic 
Dichlorvos (DDVP) Nuvan, Vapona 
Fenitrothion  Folithion, Sumithion  
Iodofenphos  Nuvanol  
Malathion  Malathion, Malagrain  
Methacrifos  Damfin  
Phoxim  Baythion 
Chlorpyrifos-methyl Reldan 
Tetrachlorvinphos  Gardona  
Source: FAO/WHO, 1994b 
 
Table 2.4: Common pyrethroids insecticides used for stored product pest control 
Active Ingredients  Brand Names 
Cyfluthrin  Baythriod  
Deltamethrin  K-Othrin 
Fenvalerate  Sumicidin  
Permethrin  Permethrin  
Source: FAO/WHO, 1994b 
 
 
 
 
 
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Table 2.5: Combined contact insecticides commonly used against mixed insect infestation in 
storage 
Active Ingredients  Brand Names 
Fenitrothion + Cyfluthrin Baythroid Combi  Baythroid Combi  
Fenitrothion + Fenvalerate  Sumi Combi 
Pirimiphos-methyl /+ Deltamethrin K – Othrine Combi 
Pirimiphos – methyl + Permethrin  Actellic Super 
Source: FAO/WHO, 1994b 
2.13.4 Use of biological control  
All insect populations tend to increase exponentially as long as there is adequate food and 
suitable environment, and no predators or parasites (Fields and Muir, 1995). Biological control 
employs the use of natural enemies such as parasites, predators or pathogens to suppress pest 
populations. Natural enemies can be classified into two types (predators and parasites) based on 
their life history, ecology and population dynamics (Brower et al., 1995). Generally, predators 
prey on individuals who are smaller than they are and feed on many preys during their life time. 
Parasites are generally smaller than their hosts and can be classified into parasitoids and micro 
parasites. Parasitoids are insects whose immature stages develop as a parasite on or in another 
insect. Microparasites are microbial pathogens such as viruses, bacteria, fungi, protozoa which 
cause contagious diseases in target pests (Brower et al., 1995). Some organisms used as 
biological control agents include: The female of the Pteromalids Anisopteromalus calandrae 
(Howard) and Choetospila elegans (Westwood) forage through stored grains, select a kernel that 
contains a larva or pupa of a grain beetle (such as the rice weevil or the lesser grain borer) 
(Brower et al., 1995). Pirate bugs such as the warehouse pirate bug, Xylocoris flavipes (Reuter), 
and the larger pirate bug, Lyctocoris campestris (Fabricius) are generalist predators whose adults 
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and nymphs feed on any life stage of pests that can be subdued (Billups, 1980). Trichrogramma 
species lay their eggs in the caterpillar of moths, e.g. C. cephalonica and Ephestia spp. (Obeng-
Ofori, 2008a). Teretrus nigriscenes (Lewis) has been effectively used to control P. truncatus in 
most countries. Females of the parasitoid wasp, Bracon hebetor (Say) seek out and sting 
wandering-stage larvae of Pyralid moth pests such as the Indian meal moth and the 
Mediterranean flour moth (Brower et al., 1995).    
Insect pathogens (microbial agents) are facultative pathogens that kill by means of insecticidal 
 proteins (toxins). Infections are acute and cause rapid mortality. For example, formulations 
  
containing Bacillus thuringiensis (Bt) kill the caterpillar stage of a wide array of moths such as 
P. interpunctella, Ephestia spp., C. cephalonica as well as the lesser grain borer R. dominica 
(Taura et al., 2004). 
2.13.5 Use of phytochemicals/botanicals     
The plant kingdom is a vast storehouse of chemical substances manufactured and used by plants 
for defence against attack by insects. These substances may elicit strong physiological responses 
in various stages of an insect‘s life. Since these naturally occurring phytochemicals are usually 
biodegradable and non-toxic to plants and animals, they offer the potential for safe and effective 
control of stored product pests (Rembold, 1994). More than 30,000 secondary metabolites have 
been reported from plants (Wink, 1988), and the major group of compounds with insecticidal 
activity are alkaloids, amines, non-protein amino acids, cyanogenic glycosides, glucosinolates, 
lectins, protease inhibitors; all of which are nitrogen containing allelochemicals. Other 
allelochemicals are monoterpenes, sesquiterpenes, diterpenes, triterpenes/steroids, tetraterpenes, 
polyketides, polyacetylenes, flavonoids and phenylpropanoids (Wink, 1993).  
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The use of locally available plant materials for stored product protection is a common practice 
and has more potential in subsistence and traditional farm storage conditions in developing and 
underdeveloped countries (Golob and Webley, 1980; Obeng-Ofori, 2007).  
In a survey in Benin, West Africa, out of 33 plants collected and tested, the powders of Nicotiana 
tabacum L, Tephrosia vogelii (Hook) F and Securidaca longepedunculata Fres significantly 
reduced progeny production of C. maculatus in stored cowpea, while Clausena anisata (Willd) 
Hook, Dracaena arborea (Willd) Link, T. vogelii (Hook) F., Momordica charantia Linn and 
Blumea aurita (Linn) F. were repellent to beetles (Boeke et al., 2004). Similarly, in a survey of 
plants used as traditional insecticides in 12 districts in forest areas of the Ashanti Region of 
Ghana involving about 500 farmers, 26 different plant species were found to be used as grain 
storage protectants (Cobbinah et al., 1999). The most common were Chromolaena odorata L., 
Azadirachta indica A. Juss., and Capsicum annum commonly used by subsistence farmers as dry 
powder and admixed with grains in the Northern Region of Ghana to protect stored maize, 
cowpea, bambara groundnut, millet and sorghum is Cassia species (Belmain et al., 1999; 2001). 
Niber (1994) also investigated the bioactivity of 10 indigenous plant species reputed to have both 
medicinal and insecticidal properties by local herbalists in Ghana against P. truncatus and S. 
oryzae. Based on the above research in Ghana, Belmain et al. (2001) reported 16 different plant 
species the Ministry of Food and Agriculture (MoFA) of Ghana has adopted to be used by 
farmers for stored product protection (Table 2.6).  
 
 
 
 
 
 
 
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Table 2.6: Plant species adopted by the Ministry of Food and Agriculture of Ghana to be 
used by farmers for stored product protection in Ghana 
1. Azadirachta indica (Neem tree)  9.  Lippia multiflora (Bush tea) 
2. Capsicum annum (Chilli pepper) 10. Mitragyna inermis (False abura) 
3. Cassia sophera (Coffee pod) 11. Ocimum americana (American Basil tree) 
4. Chamaecrista nigricens (Partridge pea) 12. Pleiocapa mutica (Kanwene-taste bitter) 
 
5. Chromolaena odorata (Siam weed) 13. Pterocarpus erinaceus (Barwood) 
6. Citrus sinensis (Sweet orange) 14. Securidaca longepeduncata (African Violet        
tree) 
7. Cymbopogon schoenanthus (Lemon grass) 15. Synedrella nodiflora (Cinderella weed) 
8. Khaya senegalensis (Mahogany tree) 16. Vitellaria paradoxa (Shea Butter tree) 
 
2.13.6 Use of plant products in stored product protection 
Application of crude extracts from many plants against pests has a long tradition in farming 
(Wande et al., 1992). Different plant products (leaves, ash, seeds, essential oils, plant oils, etc.) 
are mixed with different food stuffs to protect them against insect pest damage (Schmutterer, 
1995; Hassanali et al., 1990; Niber, 1994; Obeng-Ofori et al., 1997). One of the best known 
examples is the neem tree, A. indica. Many parts of the neem tree including the leaves, bark and 
the seeds are used for plant protection purposes in many parts of the tropical world. The seed 
kernels are rich in oil, which even at extremely low concentration as a water emulsion, deter 
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insect larvae from feeding and interfere with reproduction, growth and development 
(Schmutterer, 1995; Addae-Mensah, 1998). 
Other plants that have shown promise for the control of storage pests include the Siam weed, 
Ocimum plant species, Mahogany tree, Candlewood, Jatropha, etc., (Bekele et al., 1997; Obeng-
Ofori and Akuamoah, 2000; Udo, 2000) vegetable oils like groundnut, coconut oil are mixed 
with grains as protectants before storage, thus protection is offered by inhibiting oviposition and 
damaging the eggs of pests (Zehrer, 1980; Obeng-Ofori, 1995). Use of jute bags impregnated 
with 10% of aqueous extract from Chenopodium ambrosiodes L. and Lantana camara L. were 
found to be very effective in reducing infestation for more than six months (Obeng-Ofori, 2007). 
Owusu (2001) reported that out of 4 solvent extracts of the roots of Z. xanthoxyloides Lam., the 
methanol (MeOH) extract caused 100% mortality of S. zeamais and C. maculatus in the 
laboratory. Yadava (1973) found that 2 and 4% emulsion of essential oil of Acorus calamus L. in 
kerosene oil, water and absolute oil were effective against Callosobruchus chinensis L. Shay and 
Ikan (1980) found that the fractionated cotton seed oil processed insecticidal activity against C. 
chinensis when applied at a concentration of 400 g/ton of stored chick peas. The fractions were 
also active against S. oryzae on stored wheat. 
 
2.14   The Bellyache bush, Jatropha gossypiifolia L. 
2.14.1 Taxonomy, distribution and ecology 
Jatropha gossypiifolia belongs to the Family Euphorbiaceae. The genus name Jatropha 
combines the Greek iatros, meaning physician, with tropheia, meaning mother‘s milk, hinting at 
the medicinal properties of the plant (Parsons and Cuthbertson, 2001). The species name 
‗gossypiifolia‘ is a combination of the Latin gossypium, meaning cotton, and folium, suggesting 
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that the leaves appear similar to those of the cotton plant (Parsons and Cuthbertson, 2001).        
Overseas, J. gossypiifolia common names include ‗cotton-leaf physic nut‘(Australia), ‗cotton-
leaved jatropha‘, ‗purging nut‘, ‗American purging nut‘, ‗wild cassava‘, ‗red fig-nut flower‘ 
(Africa), ‗damar merah‘ (Indonesia) and ‗castor oil plant‘ (erroneous), bellyache bush, black 
physic nut, castor bean, red physic nut, Spanish physic nut tree, wild physic nut; local common 
names include, lapalapa pupa (Africa), aburokyi-raba, akandedua, babatsi, dkrakpoti, edmebii, 
gbomagboti, kaagya, kiti-gbleteo, kpitikpiteo (Ghana). 
Jatropha gossypiifolia is native to Brazil and tropical America from Mexico to Paraguay and the 
Caribbean region (Gardner and Bennetts, 1956). The Missouri botanical garden‘s ‗TROPICOS‘ 
database holds 84 records of the plant from Central America (Costa Rica, Honduras and 
Nicaragua), South America (Bolivia, Colombia, Ecuador, Paraguay, Peru and Venezuela), the 
Caribbean (Dominican Republic, Puerto Rico and Leeward Islands) and West Africa (Cameroon 
and Ghana) (Irvine, 1961; Chadhokar, 1978; Holm et al., 1979; Dehgan, 1982; Swarbrick, 1997). 
It was imported into Australia in the late 1800‘s, probably as a garden ornamental and had 
naturalized in Queensland by 1912. It is a major weed in Australia grown as fence, and also 
found in waste places, by the road sides and fallow lands. It occurs throughout tropical Africa, 
except the dry regions in southern Africa, but including South Africa. Introduced to southern 
Africa, the plant has spread from Mozambique through Zambia to the Transvaal and Natal. In 
West Africa, it is listed in the exotic flora of Chad (Brundu and Camarda, 2004), Cameroon and 
Ghana (Csurhes, 1999).  
It is a bushy, gregarious shrub up to 1.8 m, 3-5 lobed, approximately 20 cm long and wide with 
leaves having a long petiole, covered with glandular hairs from the euphorbiaceous family. The 
stem is hairy and nonwoody. Flowers are red-crimson of purple in corymbs, with greenish seed 
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in smooth, glabrous, oblong capsule (Plate 2.13). The plant‘s leaves are arranged alternately 
along the stem.  Leaf petioles are 2-7 cm long and the leaf blades are palmately 3-5-lobed, 45-90 
x 50-130 mm; the lobes are more or less elliptic (Wheeler, 1992). Immature leaves are deep 
purple and sticky (Plate 2.14).  Older leaves are generally glossy green although some may have 
a purple colouration (Pitt and Miller, 1991).  Petioles and leaf margins are covered with coarse, 
gland-tipped, sticky brown hairs.  Because of its deep purple immature leaves, this weed tends to 
be readily noticed by landholders.                                         
                        
Plate 2.13: Older leaves with seeds and                             Plate 2.14: Immature leaves of 
                  flowers of J. gossypiifolia                                     J. gossypiifolia                                  
 
2.14.2 Uses  
The major benefits of J. gossypiifolia are associated with its medicinal attributes. Roots, stems, 
leaves, seeds, and fruits have been widely used in traditional folk medicine in many parts of 
western Africa (de Padua et al., 1999; IPCS INCHEM, 2004). Extracts from the plant have been 
used to treat a number of human ailments, ranging from anaemia, vertigo, worms, leprosy, 
leukaemia, dysphonia, urinary complaints, ulcers, itches, conjunctivitis, dermatitis, gout, 
snakebite and venereal diseases (Irvine, 1961; Kupchan et al., 1976; Morton, 1981; Liogier, 
1990; Das and Das, 1994; Horsten et al., 1996; de Padua et al., 1999). The leaves are purgative; 
applied to boils, carbuncles, eczema and itches. Sap exudates taken from leaf petiole is mixed 
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with molasses and given to cure dysentery. Seed oil is used in skin diseases and as an external 
stimulant in rheumatism and paralytic affections. Regular brushing with the twigs keeps the teeth 
and gum disease free and cures toothache (Yusuf et al., 2009). Dried residue of MeOH extract of 
fruits is mollucidal. Seed, leaf and bark extracts are active against stored-grain pest (Asolkar et 
al., 1992). In parts of Africa, the plant is the object of superstition and is believed to ward off 
lightning (Dalziel, 1948; Ogbobe and Akano, 1993).  
Since the 1970s, various parts of the plant have been studied as a source of novel medicinal 
drugs, including potential anticancer drugs (Biehl and Hecker, 1985; de Padua et al., 1999). For 
example, anti-leukemic compounds have been isolated from the plant‘s roots (Taylor et al., 
1983). Other potential uses that have been investigated include a source of oil for energy (Forni-
Martins and Cruz, 1985), a source of plant food for human and animal consumption, an additive 
for plastic formulations (Ogbobe and Akano, 1993) and a source of insecticides (Prasad et al., 
1993; Chatterjee et al., 1980).  In Asia, the plant is used for lamp oils and dye (Smith, 1995). In 
Peru the leaves and latex are used to treat abscesses, tonsillitis, asthma, diarrhoea, toothache, 
fever, gingivitis, fungal skin infections, inflammations, burns and coughs (Pinedo et al., 1997). 
In certain African countries, people are accustomed to chewing seeds of J. gossypiifolia when in 
need of a laxative (IPCS INCHEM, 2004). The seeds are oily, purgative and emetic (Irvine, 
1961). Tea made from bark is used in Nigeria to cure intestinal worms (Irvine, 1961). The leaves 
are boiled up and used as a bath for fever and the leaves are used as a purgative in Jamaica 
(Irvine, 1961; de Padua et al., 1999). Roots of J. gossypiifolia have been used for treatment of 
leprosy (Das and Das, 1994; Baxter, 2000). Plant parts used for healthcare in India include the 
young stem, root, bark and latex (Das and Das, 1994). These parts are used either alone or with 
other components for the treatment of abdominal discomfort, bone fracture, toothache, 
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conjunctivitis, open wounds, diarrhoea, dysentery, haemorrhoids, intra-uterine death, muscular 
pain, rheumatism, tongue sores and infections around fingernails and toenails (Banerji et al., 
1993; de Padua et al., 1999).  
Crude hot water extract of J. gossypiifolia exhibited anti-malarial properties. It was capable of 
100% inhibition of the malaria agent Plasmodium falciparum (Gbeassor et al., 1989). Extracts of 
J. gossypiifolia have a reputation as a cancer cure (Biswanth and Ratna, 1995; Biswanth et al., 
1996; Morton, 1981, 1982; Taylor et al., 1983). For example, on the island of Aruba, people 
believe that a decoction of the stems from J. gossypiifolia cures throat cancer (Morton, 1982). 
Derivatives of the diterpene jatrophone were also isolated from roots of J. gossypiifolia and 
shown to have anti-tumour properties in vitro (Taylor et al., 1983). Oil extracted from J. 
gossypiifolia seeds are also used as an illuminant in Africa (Burkill, 1994). 
In drier regions of West Africa, J. gossypiifolia is used as a hedge around villages to protect 
them against bush fires (Irvine, 1961; Ogbobe and Akano, 1993). Some West Africans also 
believe that J. gossypiifolia has magical powers that protect against snakes, lightning, and 
violence (Burkill, 1994). In Senegal a decoction of the leaves is taken to treat colic, stomach-
ache and fever, including malaria. In Ghana the leaves are used as a purgative, and the leaf sap is 
applied to the tongue of babies to treat thrush and to inflamed tongues of adults. The pith of old 
stems is inserted into the nostril to cause sneezing to cure headache. In the Caribbean the plant 
sap is traditionally used in the treatment of cancer. In the West Indies an infusion of the stem is 
taken to treat hypertension. 
Since the plant has excited considerable interest because of its medicinal activity and novel 
metabolites (Das and Das 1994), biochemical companies, or other private interests, in Australia 
may eventually seek to cultivate the plant. Most parts of the J. gossypiifolia plant contain toxins 
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of various concentrations, posing a serious human health risk. Detrimental effects on human 
health include seed poisoning (Kingsbury, 1964), dermatitis (Souder, 1963) and sneezing (Irvine, 
1961). Whilst numerous cases of severe poisoning have been reported from the plant‘s native 
range, no human deaths were recorded (Begg and Gaskin, 1994). Although all parts of J. 
gossypiifolia are considered toxic, the seeds are especially so (Gardner and Bennetts, 1956; 
Oakes and Butcher, 1962; Kingsbury, 1964; Marcano-Fondeur, 1992; Wheeler et al., 1992; IPCS 
INCHEM, 2004). Main toxins include purgative oil and curcin, which is found mainly in the 
seeds and also in the fruit and sap (Chopra and Badhwar, 1940; Simonsen, 1945; Gardner and 
Bennetts, 1956; Morton, 1981; Joubert et al., 1984; Marcano-Fondeur, 1992; Burkill, 1994; 
Parsons and Cuthbertson, 2001; IPCS INCHEM, 2004). Curcin is similar to ricin, the toxic 
protein of castor oil plant (Ricinus communis). Leaves contain flavonoids, a saponin, a resin, 
tannin and triterpenes. They also contain flavonoids, vitexin, isovitexin and apigenin. Roots 
contain antileukemic and tumour-inhibitor macrocyclic diterpene, jatrophone and jatropholones 
A and B. Bark contain β-sitosterol. Roots, stems and seeds contain arylnaphthalene lignan and 
the lignan prasanthaline. Cyclogossine, a cyclic heptapeptide, had been isolated from the latex of 
the plant. Stem contains a novel lignan; jatrodien (Ghani, 2003; Rastogi & Mehrotra, 1993). It 
has toxic content ricinine and jatrophin. It is used for toothache, leprosy, ulcers, skin itches etc. 
When consumed in excess it produces abdominal pain, ptosis, and hind-limb paralysis. 
2.15 The Siam weed, Chromolaena odorata (L) King and Robinson 
 2.15.1 Taxonomy, distribution and ecology 
Chromolaena odorata is a species of flowering shrub in the Sunflower Family, Asteraceae. The 
genus name ―Chromolaena‖ is (Latin for 'fragrant, smelling nice', referring to smell the plant 
emits when damaged). The common names of the plant include agonoi, hagonoy (Philippines), 
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Bitter bush, Christmas bush, Chromolaena (Swarbrick, 1997), Common floss flower, Jack in the 
bush (Vander Velde, 2003), Siam weed, Triffid (English), Siam-raut (German), Herbe du Laos 
(French), Rumput belalang, Rumput golkar, Rumput putih (Indonesia) (U.S. Dept. Agr. Res. 
Serv., 2011). There are several local names of C. odorata in Ghana. However, one, 
'Acheampong', is most commonly used in areas where it occurs. This is probably because the 
weed became prominent during the military regime (1972-78) of General I.K. Acheampong. It is 
also known as 'Busia' especially in the Western and Central regions. Dr. K.A. Busia was a head 
of state in Ghana around 1969, when the weed was first discovered at Legon Botanical Gardens. 
It is native to North and Central America, from Florida through the West Indies and from Texas 
to Mexico and the Caribbean (Howard, 1989; Liogier, 1997) and has been introduced to tropical 
Asia, West Africa, and parts of Australia where it was first identified in 1994 with infestations 
along the Tully River and near Mission Beach, in North Queensland (Pacific Island Ecosystems 
at Risk, 2001). In its native range, it is frequently seen on roadsides, riverbanks, vacant lots, 
abandoned farmland, and neglected pastures. Christmas bush has found a particular niche in the 
slash-and-burn agriculture cycle (Ohtsuka, 1999). The species is not shade tolerant and will not 
grow under a closed forest stand (Binggeli, 1999).  
In the tropics of Africa and Asia Siam weed is a major pest of crops such as coconuts, rubber, 
tobacco and sugar cane. Siam weed is now a serious weed in Mauritius, India, Sri Lanka, south-
east Asia, China, the Philippines and Guam. It was first reported in Africa in the 1940s. Today, it 
is a major weed in Nigeria, Ghana, Cameroon, Zaire and South Africa. It has become a major 
weed in parts of Asia and West, Central and South Africa (Muniappan, 1988). It was introduced 
to Nigeria in the 1940's, and by the late 1960s, C. odorata had become an important weed. It has 
since spread to Ghana, Cote d'Ivoire and Cameroon (Cruttwell, 1988). In Ghana, the weed was 
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first discovered in February 1969, in old abandoned experimental plots in the Legon Botanical 
Gardens (Hall et al., 1972). By 1972 it had spread to the Greater Accra, Central and Western 
regions. The plant can be poisonous to livestock killing more than 3000 cattle annually in the 
Philippines, as it has exceptionally high level of nitrate in the leaves and young shoots; the cattle 
feeding on these die of tissue anoxia. The toxin also causes abortions in cattle and is suspected of 
being a fish poison (Sajise et al., 1974). 
Siam weed is recognized as one of the world‘s worst tropical weeds due to its quick invasion and 
establishment. It invades and out-competes pastures, crops and native vegetation. It has an 
extremely fast growth rate (up to 20 mm a day) and prolific seed production producing up to 
87,000 seeds per plant. It also has the potential to increase the fuel load in bushfires and it can 
cause allergic reactions. 
Siam weed is an erect or sprawling fast-growing perennial shrub, forming dense tangled thickets 
from 1.5 metres to seven metres high. It is also known to grow up to 20 metres high as a 
climbing plant. Its leaves are almost triangular, 5-12 cm long, with forward facing serrations on 
the margins (Plate 2.15). They emit a pungent odour when crushed. The stem has soft pith. White 
to pale lilac flowers occur in flat-topped clusters during winter. Seeds are brown to black, 4-5 
mm long, with parachute-like white hairs (pappus) at the top of the seed. They also contain fine 
barbs, which mean they readily stick to clothing, equipment and animals. The seed is very light 
and is subject to widespread dispersal by wind and water.  
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Plate 2.15: Leaves, flowers and stem of C.odorata 
2.15.2 Uses 
Despite the menace caused by C. odorata (Timbilla, 1996) it is claimed to be of some use in 
agriculture, land conservation and medicine. As a herbal medicine, the young leaves are crushed 
and used to treat skin wounds in Indonesia. The leaf extracts with salt are used as a gargle for 
sore throats and colds. It is also used to scent aromatic baths (Liogier, 1990). Extracts of 
Christmas bush have been shown to inhibit or kill Neisseria gonorrhoeae (the organism that 
causes gonorrhoea) in vitro (Caceres et al., 1995) and to accelerate blood clotting (Triratana et 
al., 1991). The liquid extract is used primarily for treating fresh wounds. Old wounds and boils 
are also treated with the weed. Another important use of the weed is preservation (embalming) of 
dead bodies in villages in Ghana. Diseases like malaria and jaundice are also said to be cured by 
drinking the boiled extract of C. odorata.  
Abdominal pains are said to be treated with liquid extracts of the weed as an enema. The weed is 
known to be effective in cleaning teeth and treating certain eye problems. It is also claimed that it 
effects abortion when used as an enema during the early stages of pregnancy, a disadvantage in 
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religious circles. Additionally, the weed is said to repel mosquitoes and snakes, and is used to 
preserve maize from rodents. Other advantages include using it to prevent soil erosion, as 
firewood especially in the western and central regions of Ghana, and as bait for trapping crabs 
when C. odorata leaves are combined with other chemicals. It has been reported to have 
antispasmodic, antiprotozoal, antitrypanosomal, antibacterial and antihypertensive activities. It 
has also been reported to possess anti-inflammatory, astringent, diuretic and hepatotropic 
activities (Watt and Brandwijk, 1962; Feng et al., 1964; Weniger and Robinean, 1988; Iwu, 
1993). Some specific phenolic compounds have been isolated from the plant (Metwally and 
Ekejuba, 1981). The medicinal values of plants lie in their component phytochemicals such as 
alkaloids, tannins, flavonoids and other phenolic compounds, which produce a definite 
physiological action on the human body (Hill, 1952). 
As an ornamental plant, it is sometimes used in shifting slash-and-burn agriculture to compete 
with Imperata cylindrica, which is harder to control. Chromolaena odorata can be used as a 
green manure and it possess insecticidal properties (GISD, 2006). During fallows between 
cultivation, Christmas bush adds copious amounts of organic matter to the soil and may reduce 
the populations of nematodes (M‘Boob, 1991). It is also useful as mulch for row crops (Swennen 
and Wilson, 1984). Fallow lands under C. odorata produce higher yields of crops such as maize 
and cassava. This is probably due to the recycling of nutrients and higher litter fall which 
improves organic matter and soil structure. This has also been reported in the Philippines (Torres 
and Paller, 1989). Farmers welcome the weed in some grassland areas because it suppresses 
grass growth. 
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2.16 Pirimiphos-methyl (Actellic) 
Pirimiphos-methyl is a phosphorothioate used as an insecticide. It was originally developed by 
Imperial Chemical Industries Ltd., now Syngenta , United Kingdom in 1967.  
2.16 .1 Structural Formula of Pirimiphos-methyl (C11H20N3O3PS) 
Pirimiphos-methyl is a related insecticide in which the methyl groups are replaced with ethyl 
groups.  
 
Other names include  Phosphorothioic acid, O-[2-(diethylamino)-6-methyl-4-pyrimidinyl] O,O-
dimethyl ester; Actellic; ENT 27699Gc; Methylpirimiphos; Methylpyrimiphos; Pirimiphos Me; 
Plant Protection PP511; Pyridimine phosphate; PP 511; Pyrimiphos-methyl; Actelic; Actellifog; 
Blex; 2-Diethylamino-6-methylpyrimidin-4-yl dimethyl phosphorothionate; O-(2-(Diethylamino) 
-6-methyl-4-pyrimidinyl)O,O-dimethyl phosphorothioate; O-(2-Diethylamino-6-methylpyrimi-
din-4-yl) O,O-dimethyl phosphorothioate; OMS 1424; Pirimifosmethyl; Silosan; Sybol 2; O-[2-
(Diethylamino)-6-methyl-4-pyrimidinyl] O,O-dimethyl thiophosphate. 
2.16.2 Identity and Properties of Pirimiphos-methyl 
Pirimiphos-methyl is a pale straw coloured liquid. It melts at 15-18°C and decomposes above 
-4
100°C. It has a vapour pressure of approximately 1 × 10  Torr at 30°C and a density of 1.157 
g/ml at 20°C. Pirimiphos-methyl is stable for up to six months at room temperature. It is 
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hydrolysed by strong acid or alkali. Pirimiphos-methyl is miscible with most organic solvents: 
methanol, ethanol, chloroform, acetone, benzene, toluene, and xylene (IPCS INCHEM, 2006). 
. 
2.16.3 Uses 
Pirimiphos-methyl is a fast-acting broad-spectrum organophosphorus insecticide with both 
contact and fumigant action. As a post-harvest insecticide, pirimiphos-methyl is the active 
ingredient in a number of insecticides used to control insect pests in stored cereal grain, seeds 
and peanuts (Obeng-Ofori and Amiteye, 2005). It can be applied as a complete admixture 
treatment directly to the grain and a seed of wheat, barley and oats or as a surface admixture to 
the same crop and does not affect the flavor, color, texture or aroma of grain. Treated grain may 
be used immediately for any feed or food purpose. 
It provides complete control of all of the following cereal pests: flour or mill moth (Ephestia 
kuhniella), grain weevil (Sitophilus granarius), saw-toothed grain beetle (Oryzaephilus 
surinamensis), cosmopolitan food mite (Glycyphagus destructor), rust-red grain beetle 
(Cryptolestes ferrugineus), common flour mite (Acarus siro), warehouse moth (Ephestia 
elutella), and flour beetles (Tribolium spp.).  
Pirimiphos-methyl has been used in many situations against stored product pests. The minimum 
effective dose against a wide range of insects is lower than most other OP on use or under 
development as grain protectant. It is potent against beetles, weevils, moths and mites, but not 
sufficiently effective against some strains of Rhyzopertha dominica. It is useful against immature 
stages within the individual grains and it appears quite effective against many lindane-malathion 
resistant strains. In the Philippines, pirimiphos-methyl was found to be an effective protectant of 
corn grains against a variety of pests especially Sitophilus spp. for 6 months. Pirimiphos-methyl 
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is more persistent in maize than in sorghum. Pirimiphos-methyl impregnated sacks are more 
effective than malathion for the control of storage pests of shelled corn (U.S. EPA, 2003).  
The efficacy of pirimiphos-methyl in controlling coleopteran pests in stored wheat has been 
reported in a number of publications. Huang and Subramanyam (2005) reported damage caused 
by coleopteran insects in the range of 9 to 99 % in non-treated wheat grains and that doses from 
4 to 8 ppm of pirimiphos methyl have reduced the damages to less than 1 %. Chawla and Bindra 
(1976) cited the existence of eight species of grain pests, resistant to the malation and that from 
seven organophosphorated insecticide and two pyrethroids tested for the control of Trogoderma 
granarium and Sitophilus spp in wheat, the best result was obtained with pirimiphos-methyl and 
phoxim. Bitran et al. (1991) reported that, from the tested insecticides for S. zeamais in maize, 
for S. oryzae in rice and wheat, and R. dominica in wheat, pirimiphos- methyl was the best 
treatment to protect maize against S. zeamais. 
In some African countries, grains are protected from insects during storage by chemical (mainly 
synthetic organic insecticides), non-chemical (including extremes of temperature, admixtures 
with oils, powders and extracts from plants) and often the integration of these control measures 
in a compatible manner to reduce their individual negative effects (Delobel and Malonga, 1987; 
Makanjuola, 1989; Don-Pedro, 1989; Denloye and Makanjuola, 1997; Ogendo et al., 2004). 
Many of these non-chemical methods are cheap, locally available and easily applicable without 
need for technical expertise. However, they are slow acting and not standardized, their use 
depending mainly on experience and tradition (Delobel and Malonga, 1987; Belmain and 
Stevenson, 2001). They are mainly used by subsistence farmers. In addition, the superiority in 
efficacy of synthetic compounds over non-chemical methods has been shown by recent studies. 
Okunade et al. (2002) reported that Pirimiphos-methyl was more potent against Rhyzopertha 
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dominica on sorghum in comparison to 12 natural plant products. Similarly, Obeng-Ofori and 
Amiteye (2005) reported that only pirimiphos- methyl showed effective control of S. zeamais on 
stored maize grains when its efficacy was compared with products from three plant species. The 
foregoing increases support for the use of synthetic chemicals, which are often quick-acting and 
persistent in the stored grain, thus ensuring long-term protection. 
2.16.3.1 Use pattern 
Pirimiphos-methyl shows activity against a wide spectrum of insect pests, including ants, aphids, 
beetles, caterpillars, cockroaches, fleas, flies, mites, mosquitoes, moths and thrips. It possesses 
only limited biological persistence on leaf surfaces but gives long lasting control of insect pests 
on inert surfaces such as wood, carpets, sacking and masonry. It retains its biological activity 
when applied to stored agricultural commodities including raw grain and nuts. Commercial uses 
of pirimiphos-methyl are now developing in a wide variety of outlets, including growing crops, 
public health and stored products. The most important potential use appears to be as a grain 
protectant and for use in the control of insect pests in stored products. When used for the control 
of stored product pests, pirimiphos-methyl is effective as a spray on structural surfaces and on 
the outside of bagged produce and as an admixture treatment. The recommended rates of 
application to bagged grain to control a complex of beetles, weevils, moths and mites are 
normally in the range 20-50 mg/kg. For admixture with small grains the recommended rate of 
application is 4 ml/L (10 ppm) except where Rhyzopertha dominica is present when a rate of  
6 ml/L is required. These are the maximum international limits for insecticide residues in grains 
that result from postharvest application set by FAO/WHO of the United Nations (Smith, 1990). 
Since the widespread development of strains of stored product pests resistant to malathion 
(Pieterse et al., 1972; Waterhouse, 1973) there has been considerable interest in pirimiphos-
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methyl which has proved effective against all known strains of malathion-resistant stored product 
insects. Pirimiphos-methyl is regarded as more than a replacement for malathion. At 
recommended rates, it is effective against a wider spectrum of insect pests, having an ability to 
destroy all forms other than eggs and to confer long-term protection. It is effective at lower rates 
of application and for much longer periods than is malathion. Malathion is also registered for use 
on coarse and small grains. However, this insecticide is not a suitable grain protectant because it 
breaks down rapidly and many stored-grain insects have developed high levels of resistance to 
the insecticide (Subramanyam & Hagstrum, 1995). 
 
 
  
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CHAPTER THREE 
3.0 MATERIALS AND METHODS 
3.1 The study area    
The study area was the Awutu-Senya District in the Central Region of Ghana. The district capital 
is Awutu-Breku, which shares boundaries at the North with the Agona District, the West with 
Gomoa District, both in the Central Region, at the East with Ga District in the Greater Accra 
Region, whilst at the South it is bothered by the Gulf of Guinea (Fig 3.1). According to the 
Ghana Statistical Service (2011), the current population of the district is about 274,584. Out of 
this population, 47.9% are males and 52.1% are females. 
There are two main vegetation zones namely the Savanna and forest zones in the district. The 
district experiences a five-month dry season starting from November to March during which 
period the dry North-East trade winds dominate the area. The dry season is followed by a seven-
month rainy season from April to October during which the South-West monsoon winds 
dominate the area. The rainfall figures of the district are low (40-50 cm) along the coast, but are 
higher in the inland with the mean annual rainfall ranging between 50 and 70 cm. The mean 
annual minimum and maximum temperatures are 22°C and 28°C, respectively. The major cash 
crops cultivated in the district are maize, yam, pineapple and cassava (Sackey, 2006; Awutu-
Senya District Profile, 2008). The topography and cropping patterns of the Awutu-Senya District 
were studied so that a representative selected area could be included after expert consultation 
with the District Director of the Ministry of Food and Agriculture (MoFA). By stratified random 
sampling, five farmers were selected from each of the five selected villages and interviewed, 
giving a sample size of twenty-five (25) maize farmers. The selected communities were Ahentia, 
Bontrase, Chochoe, Kroebogyir (Senya) and Kwai- Blagu. 
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3.2 The survey  
A formal survey based on a written questionnaire was conducted for five weeks. The 
questionnaire (Appendix 1) was pre-tested and modified to suit farmers‘ understanding and to 
make it easier to analyze.  
During the first time visit when the maize was harvested, samples were taken and the moisture 
content determined before produce was put in stores. The questionnaires and observations from 
the field were used to obtain information on the causes of losses. Questionnaires comprised both 
open and closed ended questions. Questions asked included: household demographics, farm 
sizes, agronomic practices (weeding, thinning, fertilizer application), harvesting period, storage 
volumes and losses, causes of losses (insect, rodent and mould damage) and marketing. The 
questionnaires were administered to twenty-five (25) farmers in the selected villages using 
stratified random sampling. Secondary information was obtained from the MoFA office at 
Awutu-Senya District (Breku) in the Central Region. 
 
 
 
 
 
  
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      Fig. 3.1: A map of Awutu-Senya District showing sampled communities  
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3.3 Determination of baseline data 
For the complex method, a baseline data covering all the moisture condition for the grains was 
determined to serve as reference point for the working samples to be used in the subsequent 
determination of losses using one of the complex methods, the Thousand Grain Mass method 
(TGM).  
The procedure used was as follows:                                                                                                                                                                                                            
About 1 kg (1000 g) maize sample was taken at the start of the storage and sieved to remove all 
unwanted materials to obtain a working sample. The moisture content was determined using the 
Protimeter Grain Master (GE Sensing, EMEA Shannon Company). The remaining working 
sample was divided into three replicate sub- samples and each counted and weighed using KERN 
572 electronic weighing scale. The baseline data or initial TGM was calculated using the 
following formula (Boxall, 1986): 
TGM1 = 10 W (100 – MC)                                                                                                                                                                                                   
                    N 
Where: TGM1 = initial Thousand Grain Mass 
                  W = wet weight of sample 
        MC = Moisture Content 
                 N = No. of grains in the sample 
3.4 Determination of grain moisture content 
Moisture content was determined from 10-15 maize cobs of varying sizes that were randomly 
selected from different parts of the maize stacks from each storage structure within the five 
communities. The maize was shelled and the moisture content was determined using the 
moisture meter (Protimeter Grain Master). The remaining grains were kept frozen for subsequent 
bioassays. 
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3.5 Chemical used as standard insecticide check 
A liquid formulation of Pirimiphos-methyl (Actellic 25 EC) containing 4 ml (10 ppm a.i.) /L was 
obtained from AGRIMAT HOUSE, Madina (a suburb of Accra, Ghana), since there is no plant 
product that has been recommended for use in controlling stored product pests. Insecticide was 
diluted in distilled water to make solutions of different concentrations for the various bioassays.  
3.6 Assessment of the bio-efficacy of C. odorata and J. gossypiifolia against major insects    
encountered during the survey 
The major storage insect pests observed during the survey were Sitophilus zeamais and 
Tribolium castaneum.  
3.6.1 Culturing of insects for laboratory bioassays 
Sitophilus zeamais were collected from naturally infested stock of maize cobs at the five selected 
farming communities in the Awutu-Senya District, Central Region and reared on whole grains in    
controlled environment at 28±2°C, 65% relative humidity and 12L: 12D photo regime (Osafo, 
1998; Weaver et al., 1998; Udo et al., 2009) in the Research Laboratory at the African Regional 
Postgraduate Programme in Insect Science (ARPPIS) Centre, University of Ghana (Plate 3.1). 
Grains were sterilized in an oven at 60°C for three hours (Santhoy and Rejesus, 2004).  Adult 
weevils (100) of mixed sexes were placed in glass jars containing 500 g of sterilized grains to 
allow oviposition. After two weeks the parent adults were removed by sieving to enable the 
emergence of same age progeny that were used for the different bioassays (Udoh et al., 2009). 
The initial stock of Tribolium castaneum was obtained from naturally infested cobs from the five 
selected farming communities, and wheat bran culture from the Entomology Laboratory 
Insectary of the Department of Crop Science, University of Ghana. One hundred adult insects of 
mixed sexes were placed in glass jars containing 500 g of sterilized grains to allow oviposition. 
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The culture was maintained in a controlled environment room at 28±2 °C, 65% relative humidity 
and 12L: 12D photo regime. After one week the parent adults were removed to enable the 
emergence of same age progeny that were used for the different bioassays (Plate 3.1).  
 
Plate 3.1:  S. zeamais and T. castaneum culture 
 
3.7 Plant materials used for the assays  
The leaves and bark of Jatropha gossypiifolia and Chromolaena odorata were used for the 
different bioassays. The leaves and bark of the plant species were collected from the wild at 
Legon, and further identified at the Department of Botany, University of Ghana. 
The plant materials were air-dried at room conditions in the screenhouse at the Sinna Garden, 
Department of Crop Science for 10 days (Plate 3.2). The materials were chopped into smaller 
pieces and milled using Retsch Verder Company (German) Milling Machine. The milled 
materials were sieved using impact test sieve with a mesh size of 710µ to obtain a fine powder 
which was used for the bioassays. 
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     Plate 3.2: Leaves and bark of plants being dried in the screenhouse 
3.8 Preparation of extracts 
Methanol and diethyl-ether solvents (100%) were used for the preparation of extracts. About  
40 g of C. odorata bark, 100 g of C. odorata leaves, 100 g each of J. gossypiifolia bark and 
leaves were mixed with 500 ml of both solvents separately and shaken using Stuart Scientific 
Flask Shaker at 200 OSC/MIN (timer 60) at the Teaching Laboratory of the Crop Science 
Department, University of Ghana for three days (Plate 3.3). Each solution was filtered and 
concentrated  using Buchi Waterbath Rotary Evaporator (B-480) at 60-70°C for methanol with 
rotary speed of 3-6 rpm for an hour, and 20-30°C for diethyl-ether with rotary speed of 2-6 rpm 
for 30 minutes according to the procedure of Godefroot et al. (1981) (Plate 3.4). After complete 
evaporation, the residues obtained were separately re-dissolved in acetone and were used for the 
different bioassay. Preliminary screenings were done using 20%, 50% and 100% concentrations 
of the extracts and the 20% was selected for the different bioassays based on the results obtained. 
The extracts were stored in the refrigerator at 8°C (Ofuya and Okuku, 1994) until ready for use.  
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Plate 3.3: Stuart Scientific Flask Shaker shaking plant materials mixed with solvents 
 
 
Plate 3.4: Rotary evaporator 
3.9 Contact toxicity by topical application 
Ten adults of S. zeamais (7-14 days old) and T. castaneum (3-7days old) were used for this 
study. The insects were chilled for three minutes to immobilise them and transferred into petri 
dishes lined with moist filter paper. One micro litre of 20% concentration of the methanol and 
diethyl-ether extracts was applied to the dorsal surface of the thorax of each insect using a micro-
pipette. Pirimiphos-methyl (1µL) of the 4 ml/L was used as a reference. Acetone was applied to 
the control insects and each treatment was replicated three times. Insects that did not move by 
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responding to three prods of a blunt probe were considered dead (Lloyd, 1969). Mortality was 
recorded after two days. 
3.10 Repellency test 
The area preference test method described by McDonald et al. (1970) was used to determine the 
repellent action of the extracts to S. zeamais and T. castaneum. Whatman No.1 filter papers  
(11.0 cm) were cut in halves (treated) and halves (untreated) – control. Concentrations (20%) of 
the extracts in acetone were uniformly applied to half of the filter paper discs with a pipette. The 
other halves of the filter paper were treated with acetone only and air-dried to evaporate the 
solvent completely (Obeng-Ofori and Reichmuth, 1997). Pirimiphos-methyl was used as 
reference product. Full discs were remade, by attaching treated halves to untreated halves of the 
same dimensions with cellotape. Each full filter paper was placed in a petri dish and 10 adult 
insects each of S. zeamais and T. castaneum of mixed sexes were released at the centre of each 
filter paper and covered (Plate 3.5). For each plant extract, there were three replicates, and the 
number of insect present on control (Nc) and treated (Nt) strips were counted and recorded after 
3 hours (Talukder and Howse, 1994). Percentage repellency (PR) values were computed as 
 % PR = [(Nc - Nt) / (Nc + Nt)] x 100 (McDonald et al., 1970); 
Where: Nc = number of insects on control 
            Nt = number of insects on the extract sides 
All negative PR were treated as zero. 
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    Plate 3.5: Insects being tested for repellence against plant extracts 
 
3.11 Toxicity of extracts on adult insects in treated grains 
The toxicity of methanol and diethyl-ether extracts against the beetles in maize grains was tested 
in the laboratory by applying 0.5 ml of extracts of dry leaves and bark at 100% concentration, 
0.25 ml each of extracts and acetone at 50% concentration and 20% concentration. Pirimiphos-
methyl (0.25 ml) was used as a reference. Sterilized maize grains (10 g) were placed into each 
petri dish and extracts were applied to grains and stirred to ensure uniform mixing and allowed to 
dry for one hour. Ten insects each of S. zeamais and T. castaneum were introduced into the 
treated and control grains and left in the controlled environment room at 28±2°C, 65% relative 
humidity and 12L: 12D photo regime. The control was treated with acetone. For each treatment, 
there were three replicates. Mortality was recorded after 4 days. Insects were considered dead 
when they did not move by responding to three prods of a blunt probe. 
 3.12 Oviposition test 
Unsexed S. zeamais and T. castaneum adults (20) were selected at random and added to 50 g of 
maize grains in glass jars and sealed with muslin cloth. They were incubated at 28±2°C ambient 
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temperature and 65% relative humidity for 7 days. After this period the parent adults were sieved 
out and 20 grains were randomly selected from each glass jar in the egg stage of both insects to 
detect grains with eggs deposited in them; that is if the insects actually laid eggs, before the 
treatment was applied using the egg-plug staining technique described by Milner et al. (1950). A 
dye solution was prepared by adding 0.5 g acid fuchsin to 5% glacial acetic acid solution. Grains 
to be treated were soaked for five minutes in warm water. The water was drained off and the 
grains were stained for two minutes (Plate 3.6). The dye solution was poured off and grains were 
washed in tap water to remove excess dye. The grains were examined to determine kernels with 
eggs deposited in them. These were identified by the presence of cherry-red stained gelatin on 
the grains (Plate 3.7). It was assumed that all grains containing eggs were plugged with gelatin. 
The number of egg plugs observed was counted and percentages of infestation level were 
recorded.   
 
                                                                
Plate 3.6: Grains covered with acid-fuchsin solution 
 
 
     
       
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       Plate 3.7: Grains examined to detect the presence of egg plugs 
 
3.13 Effect of extracts on immature stages of S. zeamais and T. castaneum 
In this experiment, ninety glass jars were filled with 50 g of maize grains each and 20 S. zeamais 
and T. castaneum adults were introduced into each jar for seven days to allow for oviposition, 
after which the parent adults were sieved out. The jars were grouped into three batches of thirty 
units. One day after the adults‘ removal, the first batch was treated with 20% of the methanol and 
diethyl-ether extracts of C. odorata and J. gossypiifolia in acetone to assess the effect of the 
extracts on the eggs using the method adopted by Udo (2000) (Plate 3.8). Pirimiphos-methyl  
(0.5 ml) was used as a reference. These treatments were replicated three times. To determine the 
toxicity of the treatments on the larval and pupal stages, the treatments were applied to the 
second and third batches one week and two weeks after adult removal, respectively. This follows 
the duration of the various developmental stages of the insects after (Hodges, 1986; Obeng-
Ofori, 2008). Grains treated with acetone served as control for each batch, and there were three 
replications for each treatment. The number of adults that emerged after five weeks of adult 
removal were counted and recorded for S. zeamais and T. castaneum.  
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Plate 3.8: Extracts being tested on immature stages of S. zeamais and T. castaneum 
 
3.14 Grain dissection to detect dead immatures 
This was done for the larval and pupal stages, after the treatments were applied to the second and 
third batches one week and two weeks after adult removal, respectively. Twenty grains were 
randomly selected from each glass jar to detect the presence of larva and pupa. The grains were 
pre-softened by soaking for two hours, then dissected with a sharp scalpel and examined under a 
microscope that revealed the presence of insects. The numbers of larva and pupa observed that 
didn‘t emerge were counted and percentages were recorded for both S. zeamais and T. 
castaneum. 
 
 
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3.15 Assessment of grain weight loss 
The loss assessment methodology based on that described by Boxall (1986) was carried out. 
Losses could be due to mouldiness of grains, attack by micro-organisms and rodents, 
discolouration of grains, and insect infestation, which appear to be the major cause of grain loss. 
Observations of rodent activity were recorded. The samples of maize in the various storage 
structures were analyzed to obtain estimates of weight loss. Damage caused by the insects was 
assessed for the treated and the control grains using the setup in Section 3.14. Before the 
experiment on the effect of extracts on immature stages, a baseline data was obtained after which 
the initial TGM was calculated (Sec.3.3). 
 After 5 weeks of storage, the final TGM (TGMx) was calculated using the procedure as follows:  
The number of grains in each glass jar was counted and weighed (Plate 3.8) and the MC was 
obtained electronically using the Protimeter Grain Master.  
The Thousand Grain Mass method (TGM) described by Boxall (1986) was used to assess weight 
loss in maize for each treatment of the egg and larval stages. The final TGM (TGMx) was 
calculated using the formula: 
TGMx =10 W ( 100 — MC )            
    N     
Where:  TGMx = TGM of the grain at time x. 
                     W = wet weight of sample; 
                   MC = moisture content (wet weight basis); 
           N = number of grains in the sample. 
The percentage weight loss was determined by using the formula as follows: 
Percentage wt loss = TGM1 — TGMx x 100        
           TGM1 
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Where: TGM1 = initial TGM (normally determined at the beginning of the storage season, also  
     called the reference sample) 
             TGMx = TGM of the grain at time x.  
3.16 Data analysis  
Different analytical tools were used for various sections of the work. Statistical Package for 
Social Sciences (SPSS version 17) was used to analyze qualitative data and data obtained from 
questionnaire. Quantitative data such as moisture content and weight loss were analyzed using 
ANOVA (Genstat Version 9) and the Least Significant Difference (LSD) was used to separate 
the means.  
th
The laboratory data collected were analyzed using Genstat Statistical Package 9.2 (9  Edition) in 
which case Analysis of Variance (ANOVA) was run using LSD at 95% confidence level. Data 
involving counts were transformed using square root (y= x) transformation, while those 
-1   
involving percentages were transformed using arcsine (y = sin x/100) transformation before 
analysis. Correction for natural mortality in control treatment was done using Abbott‘s (1925) 
formula: 
Mx    = (Mt - Mc) x 100                        
 100-Mc 
Where: Mx = corrected mortality (%) 
  Mt = mortality in treatment 
  Mc = control mortality 
 
 
 
 
 
 
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CHAPTER FOUR 
4.0 RESULTS 
4.1 Farmers’ knowledge and perception concerning postharvest losses in maize 
4.1.1 General background of maize farmers in the Awutu-Senya District 
The general background of maize farmers indicated that majority (68%) of the farmers were 
males and 32% were females (Fig. 4.1).  
 
male
17 
8 
female
 
Fig. 4.1: Gender of maize farmers in Awutu-Senya District 
 
Figure 4.2 indicates that majority of the farmers (60%) were in the age range of 41-60 years and 
8% were less than 20 years old. 
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60 
60
50
40
30 20 
20 12 
8 
10
0
Less than 20 yrs 21 to 40 yrs 41 to 60 yrs Over 60 yrs
Age of farmers 
 
                    Fig. 4.2: Age of maize farmers in the Awutu-Senya District 
 
On the level of education, 24% had no formal education, 44% of the farmers were educated up to 
the primary level, and 12% had Senior High School (SHS) education (Fig 4.3). 
44 
50
40
24 
30 20 
20 12 
10 0 
0
No formal Primary JHS SHS Tertiary
education
Level of education 
 
Fig. 4.3: Educational level of maize farmers in the Awutu-Senya District 
 
A greater percentage of the farmers (44%) have been in maize farming for 6-10 years and about 
32% of them have been farming for 11 years and above (Table 4.1). 
 
 
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% of maize farmers 
% of maize farmers 
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Table 4.1: Farmers‘ farming experience in the Awutu-Senya District 
Farming experience (years) Percentage of maize farmers 
1-5 24 
6-10 44 
11-25 16 
26 and above 16 
Total 100 
 
4.2 Production, harvesting and postharvest practices 
4.2.1 Maize varieties grown by farmers 
Maize was the predominant crop grown as farmers used more than 50% of their land for its 
production. In order to minimize risk, the farmers also grew other crops including cassava, 
pineapple and yam. However, most (48%) of the farmers in the district produced maize in larger 
quantities, while the least produced was beans.  
Farmers, when asked to indicate their reasons for cultivating maize, majority (96%) of them were 
farming to sell the produce, and the remaining respondents (4%) cultivated maize for household 
consumption.  
Most of the farmers had the intention of cultivating maize for commercial purposes, but the 
ability to expand their production was affected by some factors. These included availability of 
land (40%) as the major challenge to them all. Other factors were longer experience, improved 
varieties, availability of funds from previous harvest and availability of labour. 
The survey report indicated that 60% of the farmers cultivated the hybrid maize variety known as 
Obaatanpa and only 8% cultivated the mixed maize (Akpossoi) variety (Fig.4.4). 
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60 
60
50
40
30
20 
20 12 
8 
10
0
local obaatanpa hybrid local + obaatanpa
Maize varieties grown 
 
                    Fig. 4.4: Varieties of maize grown by the farmers in the district  
 
4.2.2 Varieties of maize grains stored 
 
There were three types of varieties of maize stored within the five farming communities: (i) 
Obaatanpa (hybrid), (ii) Abasa (local) and (iii) mixed maize (Akpossoi-not common) (Plates 4.1-
4.3). Samples of the different varieties of maize were collected from the five villages and shelled 
to determine the moisture content. 
                         
Plate 4.1: Obaatanpa (hybrid)                                            Plate 4.2: Abasa (local) 
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                                           Plate 4.3: Mixed maize (Akpossoi)  
 
4.2.3 Training of farmers by AEOs 
About 72% of the farmers indicated that they have been visited by Agricultural Extension 
Officers, and have received training on when to harvest, dry and store their maize, while 28% of 
them have never received any training (Table 4.2). Four out of 25 farmers indicated that they do 
not plant their maize in rows using recommended spacing (Table 4.2). Twelve (48%) of the 
farmers used sticks to prepare their land and about 28% of them used a tractor for tilling their 
land for cultivation. 
 
Table 4.2: Visit by AEOs and farm training 
                 Visit by AEOs Planting in rows with Receive training on when to 
 recommended spacing  harvest, how to dry and store  
maize 
Yes  18                  21               18 
No    7                   4                 7 
Total   25                  25               25 
AEO- Agricultural Extension Officer 
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4.2.4 Harvesting and storage 
The time for harvesting maize from the field varied from farmer to farmer depending on the 
availability of labour.  However, the average time for harvesting was between 4-5 months after 
planting (Table 4.3). Nineteen (19) out of 25 farmers harvested their crop 4 months after 
planting. Only 3 farmers left their crops in the field for up to 5 months after planting to dry 
before harvesting. The remaining 3 farmers harvested their crops between 4 and 5 months after 
planting. The survey report also indicated that 56% of the farmers stored the hybrid maize 
variety (Obaatanpa) while only 44% of them stored the local variety (Abasa) (Fig 4.5). 
 
Table 4.3: Farmers‘ time of harvesting 
Months after planting          Freq.                        Percentage of maize farmers 
 4 months                                   19 76 
4 .5 months                                  3        12 
5 months                                      3 12 
Total                                           25 100 
44% 
56% Local
Obaatanpa
 
Fig. 4.5: Maize varieties stored by the farmers in the Awutu-Senya District 
 
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4.2.5 Postharvest practices before storage 
Postharvest practices in the production of maize include harvesting, transporting of grain from 
the field to the house, dehusking, drying, threshing, shelling and drying before the maize were 
put into store. Majority (64%) of the farmers stored the maize with husks while some (32%) 
shelled the grains before storage. However, a few (4%) of the farmers stored in cobs (without 
husks) (Table 4.4). 
Table 4.4: Nature of stored grains 
Maize stored in cobs  Frequency                      Percentage of maize       
or shelled                                                   Farmers 
cobs (with husks)                         16 64 
cobs (without husks)                     1 4 
  
shelled grains                                8 32 
  
Total                                          25 100 
       
Most (52%) of the farmers kept some of the maize for seed while about 48% of them did not.  
About 52% of the farmers kept between 6 to 18 kg of the Obaatanpa maize variety for seed and 
stored none of the other maize varieties (Table 4.5).  
Table 4.5: Maize kept for seed 
Varieties of maize kept  Cumulative     
Maize kept as seed 
as seed percent 
 Yes 13 Obaatanpa 13 52 
No 12 None 12 48 
Total 25 Total 25 100 
 
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About 28% of the farmers stored surplus maize due to high cost of seed maize and available 
number of traditional cribs. Others stored for other reasons (Table 4.6). 
 
Table 4.6: Reasons for storing surplus maize in the district 
Reasons Percentage of maize farmers 
High cost of seed maize 28 
Good germination assessment 4 
Support to grow more maize 16 
Successful harvest 8 
Available number of traditional cribs 28 
Adequate land 16 
Total 100 
 
The maize farmers (44%) indicated that they stored their maize to obtain good price, and few of 
them (12%) attributed it to avoiding shortage of food (Table 4.7). 
Table 4.7: Reasons for storing maize 
Reasons for storage                         Frequency Percentage of maize farmers 
Avoid spoilage                                          5                                20    
High price                                                11                                              44 
 
Food                                                           6 24 
 
Avoid shortage of food                              3 12 
Total                                                         25                                               1  0  0                             
  
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Some of the farmers (76%) do not store enough maize due to lack of funds and insect infestation 
(Table 4.8). 
 
Table 4.8: Reasons for storing low quantity of maize in the district 
Reasons Percentage of maize farmers 
High insect infestation  24 
Lack of funds 76 
Total 100 
 
4.3 Storage structures 
The types of storage structures commonly used by maize farmers in the district are shown in 
Plates 4.4-4.6. Plate 4.7 shows the general arrangement of maize cobs in the storage structures. 
Table 4.9 indicates that among the common storage structures existing in the study area, the 
room stores, traditional ewe barns with polythene cover and cribs were used for maize storage by 
majority of the local farmers. The bonko and agbalugu were the least (8%) used by the farmers.  
          
Plate 4.4: Room storage 
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Plate 4.5: Traditional crib 
 
Plate 4.6: Traditional Ewe barn with polythene cover 
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Plate 4.7:  Arrangement of maize cobs in storage 
 
Table 4.9: Types of storage structures commonly used by maize farmers in the district 
Type of storage structure Percentage of maize farmers 
Bonko 8 
Agbalugu 8 
Traditional barn 28 
Crib 24 
Room 32 
Total 100 
 
  
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4.3.1 Characteristics of the three storage structures 
4.3.1.1 Room storage 
The height of this structure ranges between 21.5 to 22.6 m, 32.8 to 33.7 m in diameter, 36 to  
40 m in length, and 32.8 to 33.7 m in width (Plate 4.4). Maize cobs were usually stacked with the 
husk-on in a semi-circular form. The larger cobs were carefully stacked on the exterior with the 
remaining cobs filling the inside column into a compact cylinder. The roofing used on the 
building was made of iron sheets which protects the maize against sun and rain (Plate 4.4). 
4.3.1.2 Traditional crib 
The height of this structure ranges between 22.5 to 25 m, 1 to 0.96 m in height above ground, 23 
to 25 m in length (Plate 4.5). The structure is supported by a 2.5 m × 2.5 m, 4 wooden legs on the 
exterior. Maize cobs were usually stacked with the husk-on in a squared-form in the crib. The 
larger cobs were carefully stacked on the exterior with the remaining cobs filling the inside 
column into a compact square as on the platform. The crib is normally covered with metal roof to 
protect the maize against sun and rain (Plate 4.5).  
4.3.1.3 Traditional Ewe barn with polythene cover 
 In this structure the height ranges between 19.2 to 20 m, 6.7 to 10 m in height above ground, 
72.5 to 97.6 m in circumference and 21.0 to 33 m in diameter (Plate 4.6). The structure is 
supported by a 0.2 cm×0.2 cm split bamboo of 20-25 wooden stands. Maize cobs are stacked 
with the husk-on in a circular form. The larger cobs are carefully stacked on the exterior with the 
remaining cobs filling the inside column into a compact cylinder. A polythene sheet was used as 
cover (Plate 4.6).  
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4.3.2 Types of materials used for construction of storage structures 
Materials used for the construction of the various storage structures included mud, wood slaps, 
bamboo, sand, cement and aluminum roofing sheets (especially for the traditional cribs and room 
stores). All the traditional cribs and traditional barns were raised on 4-10 wooden stands, at least 
1 m above the ground. The materials used for construction of stores in all the five communities 
were all obtained locally, except in the few cases where stores are constructed using cement and 
galvanized zinc sheets. 
4.3.3 Age of grain stores 
The various storage structures currently used by farmers in the district were room stores, 
traditional cribs and traditional Ewe barns with polythene cover. These are presented in Plates 
4.4- 4.6. Plate 4.7 shows the conditions under which maize are stored which make them liable to 
rodent attack. 
Although the age of farmers‘ stores in the area of study ranged from 1-25 years, most of them 
were 1-5 years old, and 12% of the maize farmers indicated that their stores were over 11 years 
(Table 4.10). 
Table 4.10: Age of farmers‘ stores in the district  
Age of stores Percentage of maize farmers 
1-5yrs 56 
6-10yrs 20 
11-15yrs 12 
16 yrs and above 12 
Total 100 
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4.3.4 Maize storage efficiency 
The storage efficiency was based on the level of losses of the weight of the grains. According to 
the farmers, the traditional cribs had the highest storage period (24 months) and showed the 
lowest level of storage losses (5.0%) (Table 4.11). The room stores were almost comparable to 
the traditional cribs in terms of storage period and levels of losses according to farmers‘ 
estimates. However, the Traditional Ewe barns were reported to have higher levels of storage 
losses and shorter storage periods when compared to the other structures (Table 4.11). 
 
Table 4.11: Storage efficiency based on grain loss and storage length 
Storage type Average storage  Average grain loss reported 
length (months) by farmers(%) 
Traditional Ewe barns 7 15.00 
Room stores 15 7.50 
Traditional cribs 24 5.0 
 
4.5 Storage losses 
4.5.1 Farmers’ assessment of storage losses 
During the study, local farmers were given the opportunity to identify common postharvest loss 
problems and the agents involved. For the causes of losses or damage to their grains in store, 
farmers mentioned insects, moulds and rodents as the most important factors (Fig 4.6). Majority 
of the farmers (80%) said insect infestation caused most of the damage to the maize. Some 
farmers (12%) mentioned rats which are mostly found in the Traditional Ewe barns, while some 
respondents (8%) said mould infection was a problem (Fig 4.6).  
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80 
80
70
60
50
40
30
12 
20 8 
10
0
Insect Mould Rat/mice
Causes of maize damage 
 
                      Fig 4.6: Causes of losses to maize during storage 
 
4.5.2 Visual observation of storage losses 
Most of the on-farm stores had old, infested grains stored next to new, clean grains. This practice 
exposed new grains to insect infestation very early during the storage period. In addition, most 
farmers did not clean their stores before storing new harvested maize. Insect infestation, exit 
holes, frass and dead insects‘ bodies were observed in the grains and stores. Few of the stores 
had moulded grains, holes in the grains caused by insects, grains turned into powder by insects, 
the presence of rodents, and webbing of grains by moths. The most important insect pests found 
to be causing qualitative and quantitative losses included the grain weevil (Sitophilus spp.) and 
the red flour beetle (Tribolium spp.). Others included the larger grain borer (P.  truncatus), the 
lesser grain borer (R.  dominica) and the grain moth (S.  cerealella) (Plates 4.8-4.12). 
Losses caused by moulds were regarded as minimal, because they only occurred during the rainy 
season when the weather was wet and farmers were not able to dry the maize to the required 
moisture content either on the farm or in the open after harvest before storage. 
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    Plate 4.8: Maize weevil, S.zeamais                             Plate 4.9: Red flour beetle, T. castaneum 
       
   
 
                                                                                                                            
 
                                                                                    
    Plate 4.10: The larger grain borer,                                       Plate 4.11: Lesser grain borer,  
                       P. truncatus                                            R.  dominica                              
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                                                     Plate 4.12: Angoumois grain moth, 
                                                                      S. cerealella  
4.6 Pests control measures by farmers 
Most of the farmers either applied chemical (52%) such as Actellic or Phostoxin to control pests. 
Drying the maize frequently, dehusking and shelling to prevent further damage by pests were 
also commonly used by farmers (Table 4.12). 
      
Table 4.12: Pest control measures used on stored maize  
Control measures Percentage of maize farmers 
Spraying the barn       12 
Use of chemical to control the insect pests        52 
Drying the maize frequently        28 
Dehusking and shelling to prevent further         8 
damage 
Total         100 
 
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4.7 Contact toxicity of extracts on insects by topical application 
The effect of the methanol and diethyl-ether extracts of J. gossypiifolia and C. odorata leaves 
and bark applied topically on adults S. zeamais and T. castaneum is summarized in Table 4.13. 
There was no significant difference in the percentage mortality of the beetles for all plants 
extracts used for the treatment. However, there was a significant (P ≤0.05) difference between 
beetles treated with methanol and diethyl-ether extracts of both plants and the control. 
Pirimiphos-methyl treatment induced 90% mortality in both insects after 48 hours (Table 4.13). 
The methanolic extract of the leaves of C. odorata against T. castaneum and J. gossypiifolia 
against S. zeamais gave 66% and 77% mortality, respectively after 48 hours. No mortality was 
recorded in the acetone control treatment after 48 hours exposure (Table 4.13).   
 
  
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Table 4.13: Contact toxicity of 20 % methanol and diethyl-ether extracts of C. odorata and J. 
gossypiifolia by topical application on T. castaneum and S. zeamais 
  
                             Mean % mortality  ±SE 
  
         
Plant part/                     
Extraction       T.castaneum        S. zeamais 
solvent        48 hours        48 hours 
     
C. odorata leaves 59.0 ± 2.2 57.0 ± 3.7 
Diethyl-ether   
   
C. odorata leaves 66.1 ± 2.7 68.8 ± 2.7 
Methanol 
  
 
C. odorata bark   
Diethyl-ether 57.0 ± 3.7 54.7 ± 2.0 
   
C. odorata bark 57.0 ± 3.7 52.7 ± 2.0 
Methanol   
   
J.gossypiifolia 47.0 ± 5.2 41.1 ± 1.9 
bark Diethyl-ether   
   
J.gossypiifolia 54.7 ± 2.0 52.7 ± 2.0 
bark Methanol 
  
 
J.gossypiifolia   
leaves Diethyl- 59.0 ± 2.2 61.2 ± 2.2 
ether   
   
J.gossypiifolia 63.9 ± 4.3 77.7 ± 6.1 
leaves Methanol   
   
Actellic 90.0 ± 0.0 90.0 ± 0.0 
   
   
Acetone control 
0.0 0.0 
     
LSD (P ≤ 0.05) 8.99 8.30 
 
 
4.8 Repellency assays 
 
The repellent effect of C. odorata and J. gossypiifolia extracts is summarized in Table 4.14. Both 
plants were repellent against the insects; however, the extracts were more repellent to S. zeamais 
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than T. castaneum. Leaf extracts gave better repellency to the beetles than the bark extracts. The 
highest repellency (83.3%) was recorded for diethyl-ether extracts of J. gossypiifolia leaves 
against T. castaneum and S. zeamais. At the same concentration, the diethyl-ether extracts of C. 
odorata bark gave the lowest repellency for T. castaneum. Tribolium castaneum and S. zeamais 
were significantly (P<0.05) repelled, 100% and 93%, respectively by the reference product 
(Table 4.14). 
 
Table 4.14: Mean % repellency of 20% of methanol and diethyl-ether extracts of C. odorata and 
J. gossypiifolia against T. castaneum and S. zeamais 
 
 Mean %  repellency ± SE 
Plant part/Extraction solvent T. castaneum S. zeamais 
   
C. odorata leaves  60.0 ± 5.8 83.3 ± 3.3 
Diethyl-ether   
   
C. odorata leaves 66.7 ± 8.8 76.7 ± 14.5 
Methanol   
 
  
C. odorata bark  
Diethyl-ether 53.3 ± 16.7 80.0 ± 0.0 
   
C. odorata bark 56.7 ± 18.6 73.3 ± 3.3 
 Methanol   
   
J. gossypiifoila bark  56.7 ± 3.3 73.3 ± 8.8 
Diethyl-ether   
   
J. gossypiifolia bark  63.3 ± 17.6   66.7 ± 13.3 
Methanol   
 
  
J. gossypiifolia leaves 
 Diethyl-ether 83.3 ± 6.7 83.3 ± 8.8 
   
J. gossypiifolia leaves  70.0 ± 5.8 73.3 ± 3.3 
Methanol   
   
Actellic 100.0 ± 0.0 93.3 ± 6.7 
   
LSD (P ≤ 0.05) 33.3  24.7  
 
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4.9 Toxicity of extracts on adult insects in treated grains 
 The toxicity of diethyl-ether and methanol extracts of the plants species on insects in treated 
grains is presented in Tables 4.15, 4.16 and 4.17. Percentage mortalities of both insects were low 
at lower concentrations of the diethyl-ether extracts of the bark of the plants. There was no 
significant difference in mortalities among the treatments.  As the concentration of the extracts 
increased, the mortality of the insects also increased. The highest mortality (68%) was recorded 
for S. zeamais after four days grain treatment with 100% diethyl-ether and methanolic leaf 
extracts of C. odorata. The same concentration caused 68% mortality in T. castaneum after four 
days (Table 4.17). On the other hand, grains treated with 50% concentration of the leaf extract of 
J. gossypiifolia caused the highest mortality of 66.1% against T. castaneum after four days 
treatment (Table 4.16), while 20% and 50% diethyl-ether leaf extracts of C. odorata induced 
66.1% mortality (Tables 4.15 and 4.16). There was no mortality in the control. Grains treated 
with actellic caused 90% mortality in the weevils.  
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.15: Mean % mortality of T. castaneum and S. zeamais exposed to grains treated with 
20% extracts of C. odorata and J. gossypiifolia after 96 hours 
 
  
  
        Mean% mortality      
Plant part/ T. castaneum  S.zeamais  
Extraction     
solvent                  Day 4 Day 4  
    
C.odorata leaves 57.0 ± 6.3 66.1 ± 4.7 
Diethyl-ether    
    
C.odorata leaves 59.0 ± 3.8 59.0 ± 3.8  
Methanol    
 
   
C.odorata bark 
Diethyl-ether 46.9 ± 3.3 48.8 ± 3.3 
 
   
 
 
C.odorata bark   
 
Methanol 48.8 ± 3.3 50.8 ± 5.9 
    
J.gossypiifolia 46.9 ± 3.3 46.9 ± 3.3  
bark Diethylether    
    
J.gossypiifolia 48.8 ± 3.3 50.8 ± 5.9  
bark Methanol    
 
   
J.gossypiifolia 
leaves Diethyl- 59.0 ± 3.8 63.4 ±0.0 
 
 
ether   
    
 
J.gossypiifolia 61.2 ± 3.8 59.0 ± 3.8 
leaves Methanol    
    
Actellic 77.7 ± 10.6 90.0 ± 0.0  
    
Acetone control  0.0 0.0  
  
    
LSD (P ≤ 0.05) 8.37 6.44  
 
 
 
 
 
 
 
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Table 4.16: Mean % mortality of T. castaneum and S. zeamais exposed to grains treated with 
50% extracts of C. odorata and J. gossypiifolia after 96 hours 
 
 
                      
                         Mean % mortality     
Plant part/     
Extraction T.  castaneum S.  zeamais  
solvent Day 4 Day 4  
    
C.odorata  leaves 61.2 ± 3.8 66.1 ± 4.7  
Diethyl-ether    
    
C.odorata  leaves 
63.4 ± 0.0 57.0 ± 6.3  
Methanol 
   
 
   C.odorata  bark 
 
Diethyl-ether 48.8 ± 3.3 50.8 ± 5.9 
    
C.odorata bark    
Methanol 52.7 ± 3.5 52.7 ± 3.5  
    
J.gossypiifolia    
bark Diethyl-ether 46.9 ± 3.3 48.8 ± 3.3  
    
J.gossypiifolia 50.7 ± 0.0 52.7 ± 3.5  
bark  Methanol 
   
 
 
J.gossypiifolia   
leaves  Diethyl- 66.1 ± 4.7 63.4 ± 0.0 
 
ether    
    
J.gossypiifolia  63.4 ± 0.0 59.0 ± 3.8  
leaves  Methanol    
    
Actellic 77.7 ± 10.6 83.8 ± 10.6  
    
Acetone control 0.0 0.0  
    
LSD (P ≤ 0.05) 7.31 8.68  
 
 
 
 
 
 
 
 
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Table 4.17:  Mean % mortality of T. castaneum and S. zeamais exposed to grains treated with 
100% extracts of C. odorata and J. gossypiifolia after 96 hours 
 
                        Mean % mortality  
                    T. castaneum                    S. zeamais 
Plant part/ 
          
Extraction 
 Day 4  Day 4 
solvent 
       
C.odorata leaves 68.8 ± 4.7 68.8 ± 4.7 
Diethyl-ether   
   
C.odorata leaves 
68.8 ± 4.7 68.8 ± 4.7 
Methanol 
  
 
C.odorata bark    
Diethyl-ether 57.0 ± 6.3 59.0 ± 3.8 
   
C.odorata bark 50.7 ± 0.0 54.7 ± 3.5 
Methanol   
   
J.gossypiifolia 54.7 ± 3.5 56.7 ± 0.0 
bark Diethyl-ether   
   
J.gossypiifolia 50.7 ± 0.0 54.7 ± 3.5 
bark Methanol 
  
 
J.gossypiifolia   
leaves Diethyl- 68.8 ± 4.7 66.1 ± 4.7 
ether   
   
J.gossypiifolia 68.8 ± 4.7 59.0 ± 3.8 
leaves Methanol   
   
Actellic 77.7 ± 10.6 90.0 ± 0.0 
   
Acetone control 0.0 0.0 
       
LSD (P ≤ 0.05) 8.57 5.89 
 
 
4.10 Detection of hidden infestation 
The degree of internal infestation was due to the presence of insects feeding inside the grains. 
Grains stained with acid-fuchsin solution and the grains dissected showed the degree of 
infestation by the number of egg plugs observed and the presence of larva and pupa respectively, 
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compared with the control. 
4.10.1 Oviposition  
The mean total number of eggs laid per 20 grains by S. zeamais and T. castaneum after 7 days 
oviposition period before treating the grains with extracts is summarized in Table 4.18. It was 
observed that T. castaneum laid more eggs than S. zeamais though the observed differences in 
the number of eggs laid by both insects were not significantly different.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.18: Mean total number of eggs laid by S. zeamais and T. castaneum per 20 grains using 
the acid fuschin egg staining technique 
  
  
Plant part/ Mean number of eggs laid ±SE  
Extraction solvent   
S.  zeamais T.  castaneum 
   
C. odorata leaves 72.6 ± 11.5 73.5 ± 8.3 
Diethyl-ether   
   
C.odorata leaves  
75.0 ± 7.9 78.1 ± 6.6 
Methanol 
  
 
C. odorata  bark    
Diethyl-ether 58.9 ± 7.7 63.2 ± 6.3 
   
C. odorta bark 55.3 ± 6.0 58.3 ± 4.8 
Methanol   
   
J.gossypiifolia bark  63.2 ± 6.3 60.7 ± 5.5 
Diethyl-ether   
   
J.gossypiifolia bark  
75.0 ± 7.9 72.8 ± 9.6 
Methanol 
  
 
J. gossypiifolia leaves   
Diethyl-ether 63.9 ± 4.3 79.5 ± 5.5 
   
J.gossypiifolia leaves  68.1 ± 11.6 68.9 ± 2.7 
Methanol   
   
Actellic 85.7 ± 4.3 85.7 ± 4.3 
   
Acetone control 76.3 ± 7.0 79.5 ± 5.5 
   
LSD (P ≤ 0.05) 23.07 18.27 
 
 
4.11 Effect of extracts on immature stages of T. castaneum and S. zeamais 
4.11.1 Effect of extracts on eggs 
The C. odorata and J. gossypiifolia extracts reduced the emergence of adult S. zeamais and T. 
castaneum in grains containing eggs of the insects (Table 4.19). A few adults emerged at 20% 
concentration of diethyl-ether and methanolic bark extracts of both C. odorata and J. 
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gossypiifolia, while there were no emergence recorded for the same concentrations of leaf 
extracts of both plant species, just as the reference product (Table 4.19). There was a significant 
(P <0.05) difference between the extract treated grains and the control. The highest mean adult 
emergence of 15.0 was recorded in the control.  
Table 4.19: Mean adult emergence (%) of T. castaneum and S. zeamais after treating eggs with 
20% extracts of C. odorata and J. gossypiifolia  
 
  
Plant part/ Mean adult emergence±SE 
Extraction solvent   
T. castaneum S. zeamais 
   
C.odorata  leaves 0.0 0.0 
Diethyl-ether   
   
C.odorata  leaves 0.0 0.0 
Methanol 
  
 
C.odorata bark    
Diethyl-ether 1.0 ± 0.7 1.0 ± 1.0 
   
C.odorata bark  1.0 ± 1.0 1.0 ± 0.6 
Methanol   
   
J. gossypiifolia bark 2.0 ± 0.9 1.0 ± 0.3 
Diethyl-ether   
   
J. gosypiifolia bark  0.0 1.0 ± 0.3 
Methanol 
  
 
J. gossypiifolia leaves  0.0 0.0 
Diethyl-ether   
   
J. gossypiifolia leaves  1.0 ± 0.7 0.0 
Methanol   
 0.0 0.0 
Actellic   
 15.0 ± 0.6 15.0 ± 0.9 
Acetone control 
   
LSD (P ≤ 0.05) 1.61 1.42 
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4.11.2 Effect of extracts on larvae 
The effect of methanol and diethyl-ether extracts of C. odorata and J. gossypiifolia on the 
developing larvae of S. zeamais and T. castaneum is summarized in Table 4.20. Generally the 
products had detrimental effect on the developing larvae as no adult emerged in all treatments 
though few adults emerged from the methanolic bark extracts of J. gossypiifolia and C. odorata, 
and diethyl-ether extracts of J. gossypiifolia but there were no significant difference among 
treatments.  
Table 4.20: Mean adult emergence (%) of T. castaneum and S. zeamais after treating larvae with 20% 
extracts of C. odorata and J. gossypiifolia  
  
Plant part/ Mean adult emergence ±SE  
Extraction solvent   
T. castaneum S. zeamais 
C.odorata  leaves   
Diethyl-ether 0.0 0.0 
   
C.odorata  leaves 0.0 0.0 
Methanol   
 
  
C.odorata bark  
Diethyl-ether 0.0 0.0 
   
C.odorata bark  1.0 ± 1.0 1.0 ± 0.7 
Methanol   
   
J. gossypiifolia bark 1.0 ± 0.3 1.0 ± 1.0 
Diethyl-ether   
   
J. gosypiifolia bark  1.0 ± 0.6 1.0 ± 0.7 
Methanol   
 
0.0 0.0 
J. gossypiifolia leaves  
Diethyl-ether   
J. gossypiifolia leaves  0.0 0.0 
Methanol   
Actellic 0.0 0.0 
   
Acetone control 14.0 ± 0.6 17.0 ± 0.3 
LSD (P ≤ 0.05)                       1.24                       1.31 
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4.11.3 Effect of extracts on pupae 
The C. odorata and J. gossypiifolia extracts were effective against pupae and significantly 
(P<0.05) reduced the emergence of T. castaneum and S. zeamais (Table 4.21). Only 1 adult S. 
zeamais emerged in the diethyl-ether leaf extracts treatment of J. gossypiifolia. Leaf and bark 
extracts of C. odorata completely inhibited the development of T. castaneum and S. zeamais. 
The methanolic leaf extract of J. gossypiifolia also caused complete mortality of pupae and no 
adult beetle emerged in treated grains. 
Table 4.21: Mean adult emergence (%) of T. castaneum and S. zeamais after treating pupae with 
20% extracts of C. odorata and J. gossypiifolia  
 
  
Plant part/ Mean adult emergence ±SE 
Extraction solvent   
T. castaneum S. zeamais 
C.odorata  leaves 0.0 0.0 
Diethyl-ether   
   
C.odorata  leaves 0.0 0.0 
Methanol   
 
  
C.odorata bark  
Diethyl-ether 0.0 0.0 
   
C.odorata bark  0.0 0.0 
Methanol   
   
J. gossypiifolia bark 0.0 0.0 
Diethyl-ether   
J. gosypiifolia bark  1.0 ± 0.7 0.0 
Methanol   
J. gossypiifolia leaves  0.0 0.0 
Diethyl-ether 
  
J. gossypiifolia leaves  
Methanol 0.0 0.0 
Actellic 0.0 0.0 
   
Acetone control 16.0 ± 1.5 15.0 ± 1.5 
 
   
LSD (P ≤ 0.05) 1.52 1.42 
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4.12 Grain dissection to detect dead immatures 
The mean number of larvae and pupae per 20 grains by S. zeamais and T. castaneum after the 
treatments were applied one and two weeks after adult removal is summarized in Table 4.22. It 
was observed that both insects treated with the diethyl-ether extract of the bark of J. gossypiifolia 
had higher percentages of pupae within the grains next to the control. The larvae of both insects 
treated with methanolic leaf extract of C. odorata and J. gossypiifolia significantly (P<0.05) 
reduced the number of larvae and pupae hatchability. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.22: Mean number of larvae and pupae of S. zeamais and T. castaneum dissected from      
stored grains 
 
     Mean % dissected larvae  and pupae ± SE 
Plant part/           
Extraction           T.  castaneum                    S.  zeamais 
solvent     Larva      Pupa Larva      Pupa 
     
C.odorata leaves  50.8 ± 3.4 42.1 ± 1.7 45.03 ± 4.4    36.2 ± 1.7 
Diethyl-ether     
     
C.odorata leaves  56.8 ± 1.8 45.0 ± 1.7 45.9 ± 2.5    39.2 ± 1.7 
Methanol     
 
    
C.odorata bark  
Diethyl-ether 53.7 ± 1.7 44.0 ± 3.5 50.7 ± 1.7    44.0 ± 3.5 
     
C.odorata bark      
Methanol 51.8 ± 3.5 37.2 ± 1.0 49.8 ± 2.6    37.2 ± 2.6 
     
J.gossypiifolia     
bark Diethyl- 55.8 ± 2.7 51.7 ± 1.0 55.8 ± 2.7    45.0 ± 3.3 
ether     
J. gosypiifolia     
bark  53.7 ± 1.7 38.2 ± 1.0 45.9 ± 2.5    39.2 ± 1.7 
Methanol 
    
 
J. gossypiifolia     
leaves Diethyl- 47.8 ± 1.7 38.2 ± 1.0 55.8 ± 2.7    38.2 ± 1.0 
ether     
     
J. gossypiifolia 53.7 ± 1.7 37.2 ± 1.0 55.8 ± 2.7    39.2 ± 0.0 
leaves     
Methanol     
   66.2 ± 3.4 64.1 ± 5.4 73.4 ± 1.8    64.9 ± 1.3 
Actellic     
     
Acetone control 
65.0 ± 3.4 58.0 ± 3.8 70.1 ± 1.5    47.8 ± 1.7 
. 
     
LSD (P ≤ 0.05) 7.78 7.55 7.77         6.19 
 
 
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4.13 Damage assessment 
Damage assessment in terms of percentage weight loss due to the feeding activities of the insects 
is presented in Table 4.23. Grains treated with the plant extracts significantly (P<0.05) reduced 
damage caused by S. zeamais and T. castaneum compared with the untreated grains. Leaf 
extracts of C. odorata and J. gossypiifolia were more potent than the bark extracts as the lowest 
weight loss caused by both insect species was recorded in those treatments compared to bark 
extracts. The methanol extract of the bark of J .gossypiifolia was the least effective after the 
control in protecting grains from damage by S. zeamais and T. castaneum (Table 4.23.). Maize 
grains were protected by the extracts for 37 days in storage with no significant difference 
(P<0.05) between the leaf extracts and Actellic, though the plant materials was generally less 
effective than Actellic.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 4.23:  Mean % weight loss caused by S. zeamais and T. castaneum on grains stored for 37 
days with 20% extracts of C. odorata and J. gossypiifolia  
 
 Mean % weight loss ±SE 
Treatment             S.  zeamais        T. castaneum 
      
Egg Larva Egg Larva 
C. odorata leaves  1.46 ± 0.1 1.14 ± 0.1  0.77 ± 0.4 0.48 ± 0.2  
Diethyl-ether     
     
C. odorata leaves  1.00 ± 0.1 0.68 ± 0.1 0.66 ± 0.3 1.15 ± 0.2 
Methanol 
    
 
    
C. odorata bark  
Diethyl-ether 1.07 ± 0.1 0.79 ± 0.1 1.15 ± 0.2 1.13 ± 0.3 
     
C. odorata bark  1.38 ± 0.4 0.94 ± 0.1 0.77 ± 0.2 0.49 ± 0.0 
Methanol     
     
J. gossypiifolia 0.68 ± 0.1 1.38 ± 0.4 0.61 ± 0.2 0.79 ± 0.1 
bark Diethyl-     
ether     
J. gosypiifolia 1.15 ± 0.1 1.07 ± 0.1 1.05 ± 0.2 0.67 ± 0.2 
bark      
Methanol 
    
J. gossypiifolia 
leaves Diethyl- 0.79 ± 0.1 0.99 ± 0.1 0.71 ± 0.2 0.86 ± 0.1 
ether     
J. gossypiifolia     
leaves 0.94 ± 0.1 1.46 ± 0.1 1.11 ± 0.3 0.71 ± 0.1 
Methanol     
     
Actellic 0.32 ± 0.0 0.26 ± 0.0 0.16 ± 0.0 0.14 ± 0.0 
     
Acetone control 6.83 ± 0.9 6.57 ± 0.5 4.47 ± 0.7 2.79 ± 0.3 
 
       
LSD (P ≤ 0.05) 0.98 0.65 0.96 0.55 
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CHAPTER FIVE 
5.0 DISCUSSION 
5.1 Socio-economic characteristics of farmers 
Farmers‘ decision to use any storage structure was influenced by factors such as sex, age, 
educational level, household size and the capacity to store (Antle et al., 1993). This study 
however revealed that the choice of the storage structures and the postharvest practices used by 
farmers was not influenced by their age, sex, educational level or household size. This could be 
related to the fact that some of them had not received any training from Agricultural Extension 
Officers in production and postharvest practices. The only social factor that influenced the choice 
of any of the storage structures was years of farming experience. For example, the use of 
traditional cribs was mostly used by experienced farmers since they knew that cribs might have 
the highest storage period (24 months) and the lowest storage losses (5.0%). Other inexperienced 
farmers use Traditional Ewe barns and room stores. 
5.2 Production, harvesting and postharvest practices 
Post-harvest practices include harvesting, gathering, transportation of grains from the field to 
homes, drying, threshing, shelling, cleaning and packaging (Golob et al., 2002). Most of the 
farmers (64%) in the Awutu-Senya District store their maize on cobs with the sheath (husks) on.  
Therefore activities such as shelling, drying, threshing and cleaning are not properly done before 
storage. Traditionally, cereal grains are stored in the dry form (Marsland and Golob, 1999). 
Drying is normally effected by leaving the matured crops in the field to dry in the sun before 
harvesting. It is noted that the cereals are harvested with a high moisture content ranging 
between 21-25% (Boxall et al., 2002). Grains are further dried in the sun (either in the field or at 
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home) after harvesting to avoid heating and fungal growth (Marsland and Golob, 1999), unlike 
what is practiced in certain parts of Ghana, especially in the Ashanti and Brong-Ahafo Regions, 
where the sheath of the maize may be removed and the cobs sorted into two lots; damaged and 
undamaged (Nyanteng, 1972). Similar differences in post-harvest practices have been reported in 
other parts of Africa (Golob et al., 2002). These differences in post-harvest handling between 
areas in a country reflect mostly farming experience and ethnicity and are not necessarily a result 
of economic or technical influences (Golob et al., 2002). 
The two major forms of storing maize have advantages and disadvantages. Insect infestation 
starts on the field (Farrell et al., 2002), thus removal of sheath makes it possible to select and 
store the cobs which have not been infested. The presence of long tight husks is known to reduce 
weevil infestation in the field (FAO, 1969; Kossou et al., 1993), and the protective function of 
husks can carry over into the maize storage period. Another advantage is that fungal growth is 
reduced as a result of a decrease in weevil infestation. Weevils facilitate the growth of 
Aspergillus flavus and aflatoxin production in maize by increasing surface area susceptible to 
fungal infection and increasing moisture content as a result of the weevil metabolic activity (Beti 
et al., 1995). Also, re-infestation can be facilitated in store where cobs are stored without sheaths 
(Farrell et al., 2002). However, storing in sheath does not allow selection to be done and hence 
both damaged and undamaged cobs are stored together. 
5.2.1 Area under maize cultivation 
The land under cultivation by participating farmers was approximately 1.2 (ha) and 83% of them 
expressed the willingness of increasing the quantity of maize they grow, though they were 
constrained by several factors including availability and size of land, sale of previous season and 
current market price of the crop. These factors make it difficult for farmers to decide the area of 
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maize to be grown and quantity that would be stored per season. This was a contradiction to 
findings of Mijinyawa et al. (2006) who reported that the quantity of maize to be stored 
depended on the quantity harvested. In view of these, farmers have resolved to farming on small 
lands as they could not get enough land to increase their productivity. 
5.3 Varieties of maize stored and farmers’ knowledge on modern farm practices 
Farmers in the Awutu-Senya District mainly store three types of maize varieties. The survey 
showed that 60% of the farmers cultivated the hybrid maize variety known as the Obaatanpa and 
only 8% cultivated the mixed maize (Akpossoi) variety. The local variety, Abasa, was also 
common in the district. 
Technology is the accumulation of knowledge that lowers cost of production and helps in 
increased output (Hill, 1990). For example, in storage-loss control, the uses of appropriate 
protectants, which reduce loss and lengthen shelf-life of grains, reduce the vulnerability to pest 
infestation (Egyir, 2003). Farmers in the study area have knowledge on improved farming 
methods such as growing of improved maize varieties, planting in rows with correct spacing and 
practising postharvest activities such as dehusking, shelling, cleaning and drying before storage. 
Rogers (1995) asserted that an individual‘s knowledge of an activity depends on factors such as 
educational level, participation in training programmes, accessibility to mass media and 
accessibility to change agent. Oloruntoba and Adegbite (2006) contended that the provision of 
extension services coupled with other factors have significant positive influence on decision to 
adopt introduced technologies with attendant improvement in productivity and the well-being of 
farmers. Thus, for a farmer to get access to a new technology the important factors are the 
change agent and the farmers‘ willingness to accept the technology. Therefore, the lack of 
knowledge on such pertinent agricultural practices could have resulted from the absence of these 
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change agents. In effect an individual‘s adoption and use of good agricultural practices is 
influenced by their ability to utilize the information, as well as the structures made available by 
relevant institutions (Oloruntoba and Adegbite, 2006). 
5.3.1 Types of materials used for construction of storage structures 
The materials used for the construction of stores in the district included mud, wood slaps, 
bamboo, sand, cement and aluminum roofing sheets, especially for traditional cribs and room 
stores. These materials were not different from those described by Nyanteng (1972) for 
traditional storage structures in Ghana. These materials were obtained locally, except in a few 
cases where stores were constructed using materials such as cement and galvanized zinc sheets. 
One of the key factors affecting efficient storage of produce is the availability of the structure to 
hold the produce, depending on the type of produce, volume of storage, technical and economic 
situations of the individuals involved in the storage (FAO, 1994b; World Resources, 1998; 
Mijinyawa, 2002; Dlamini, 2003). The effectiveness of storage structures in any farming 
communities is related to the availability and affordability of its construction materials as well as 
the appropriateness of the technology and its efficiency (Itto and Wongo, 2002). 
Out of the different types of storage structures, the Traditional Ewe barns, room stores and 
traditional cribs were the three commonly used storage types in all the sample communities. 
With the exception of room stores, the other two structures do not last very long since the roofs 
require replacement every season. The traditional storage structure systems and practices used by 
farmers in the study area have evolved over many generations to keep grains cool, dry and safe 
from pests attack. Despite adaptations, pests often find their way to the stored grain, so farmers 
have to ensure good grain conditions and quality through sun-drying, spraying or applying 
chemical, dehusking and shelling to prevent further damage against pests and rodents. 
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These materials were observed to be non-resistant to one form of deterioration or the other. 
Walls of some of the rooms used as grain stores were constructed from either mud or bricks, and 
as such, they were subject to rain erosion and in some cases cracks on the walls induced water 
getting into the rooms. Natural fibers are prone to fire hazards. They are also liable to decay due 
to weathering and insect attack. Wood products were substantially used for construction because 
of their local availability and ease of use though breakages and decay were some problems 
identified with their usage. Some of the wood species were claimed to be naturally durable and 
were often used untreated. They were therefore often attacked by insect pests since no attempt 
was made to apply any preservatives. Those used as columns for traditional cribs were prone to 
either buckling or breakage due to overloading. Where metal roof is used, corrosion is a common 
problem, especially around the nail points, which may lead to leakage. 
5.3.2 Maize storage efficiency 
The efficiency of storage systems was determined by storage length and losses that are incurred. 
Maize storage methods used by households were inefficient except for traditional cribs and the 
room stores. The majority of the farmers using the various storage structures said they did not 
intend to change the type of storage method used despite the problems associated with their 
usage. The average storage length stated by farmers varied and ranged from 5 to 8 months, 
indicating that the grain is commonly sold or consumed prior to or by the time new season‘s 
maize is ready for harvesting. Maize storage has the potential to smoothen food supply between 
harvests (Thamaga-Chitja et al., 2004), but seemingly insufficient produce is stored to take 
households through to the next season. Some of the farmers in the study area reported purchasing 
additional maize to take them to the next crop harvest, and this highlights the inadequacy of 
production and storage systems. Farmers could not accurately estimate storage losses making it 
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difficult to determine the proportion of maize lost due to deterioration in storage. However, 
respondents reported maize losses in storage to be ranging from 7-15%. It is therefore difficult to 
determine if food supply is constrained by inadequate production or if production is constrained 
by storage potential and if storage potential is limited by maize deterioration. 
FAO (1994a) reported that there had been a tendency to over-estimate storage losses, and to base 
estimates on extreme cases or guess-work rather than on sound empirical testing. Figures of     
30% or more are not uncommon for grains, 50% for roots and tubers and 100% for perishable 
crops such as fruit and vegetable crops (FAO, 1994a). Ghana‘s crop loss level has been 
estimated at a global 30 percent or more (Egyir et al., 2008). Even if these figures are 
exaggerated, FAO (1994a) suggests that food losses as low as 5% should not be ignored. This is 
because such losses are usually accompanied by qualitative losses which affect the whole mass 
of the grain in store. Moreover, the losses are mainly experienced during the lean season before 
the new harvest is ready, thereby having an adverse effect on the food security of farming 
families at a particular critical period. 
The Traditional Ewe barns were comparatively cheap to construct, maintain and easily accessible 
to respondents, and hence widely used. Although these structures can store grain for more than 
six months, higher losses make this storage method inefficient. The average storage length for 
Traditional Ewe barns was much lower than that of the traditional cribs. Thus, increased use of 
traditional cribs could extend the availability of maize for households in the district. Therefore, 
traditional cribs may increase household food security but it is less accessible to poorer 
households because of the high cost and labour involved in their construction. The storage length 
of maize in room stores was almost comparable to the average storage length of maize in 
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traditional cribs. However, respondents using this structure reported losses higher than those of 
the traditional cribs. 
5.4 Maize losses incurred by farmers  
Losses‘ estimates reported by the farmers in the district varied widely. The estimates could 
hardly be correlated with the length of storage. While the estimated losses tend to vary, it was 
noted that there was similar range within which most of the estimated figures fell. While it is 
now generally accepted that the traditional local storage systems are usually well-adapted to 
local conditions and losses from grain are generally low and acceptable to farmers (Compton, 
1992), farmers surveyed estimated between 5 to 15% of maize stored in the various storage 
structures. The farmers using the Traditional Ewe barns reported higher losses and the lowest 
was reported by farmers using the traditional cribs. These estimates are consistent with those 
reported by Reusse (1968), Rawnsley (1969), Nyanteng (1972), Armah and Asante (2003) and 
Egyir et al. (2008). However, the estimates reported by these farmers were higher than those 
obtained by this author using standard laboratory methods. Most farmers in the area of study 
considered storage losses caused by insects and rodents as serious, and those caused by moulds 
as minimal. The two commonest insects reported by the farmers were the maize weevil, S. 
zeamais and the red rusty flour beetle, T. castaneum, though S. zeamais is a key pest since 
farmers appear to be more familiar with it than T. castaneum. Other insect pests reported by 
farmers were P. truncatus, S. cerealella and R. dominica. The farmers‘ opinion that S. zeamais 
was the most destructive corroborates reports in Ghana, that out of an estimated total annual 
harvest of 250,000-300,000 tonnes of maize about 20-25% is lost to S. zeamais alone (Ayertey, 
1982; Obeng-Ofori and Amiteye, 2005). 
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It was observed that farmers did not store new, clean grains separately from old, infested grains 
in their stores. Additionally, farmers did not clean their stores before storing new harvested 
maize. All these bad post-harvest practices contributed to maize losses in the stores.  
5.5 Pests control measures by farmers 
Most of the farmers in the Awutu-Senya District use different pest control measures such as 
treatment with Actellic or phostoxin, drying the maize frequently, dehusking and shelling to 
prevent further damage. It was also observed that most of the farmers (52%) in the study area 
applied chemicals for preservation. However, sampled grains showed to a larger extent the 
presence of insects. It was observed that most of the farmers had been trained in the past by 
MoFA Extension Officers on the use of insecticides (synthetic and botanicals). However, the 
farmers were not applying the chemicals as recommended by the manufacturers. Most of the 
farmers could not read the label and apply the recommended chemical at the required quantity. 
Some of the farmers have been made to believe by the chemical peddlers that these chemicals are 
not toxic to humans. Furthermore, respondents believed the liquid does not get into the maize 
itself since it is just sprayed on the grains or around the sacks.  
5.6 Contact toxicity of extracts on insects by topical application 
The concentration of the methanol and diethyl-ether extracts of the leaves and bark of C. odorata 
and J. gossypiifolia were bioactive against S. zeamais and T. castaneum when applied topically 
on them and monitored for 48 hours, though the leaves of both plants were significantly more 
potent than the bark. The extracts in the present study were more toxic to T. castaneum than S. 
zeamais. The effectiveness of the extracts indicates a positive contact action of the active 
constituents in C. odorata and J. gossypiifolia. In a similar study leaf extracts of J. gossypiifolia 
were shown to be toxic to T.  castaneum (Herbst) (Coleoptera: Tenebrionidae) and Phenacoccus 
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herreni William & Cock (Sternorrhyncha: Pseudococcidae) (Dev and Koul, 1997; CIAT, 2001). 
Using Jatropha curcas L. (Euphorbiaceae) extracts, a 20% concentration was required to cause 
70 to 90% mortality in beetles (Asmanizar and Idris, 2012). Thus, insect susceptibility to the 
extracts may depend on mode of administration, chemical composition of the constituent 
compounds and their structural features (Bell, 1986).  
5.7 Repellent effect of extracts on insects 
The various plant extracts were repellent to S. zeamais and T. castaneum relative to the control. 
The diethyl-ether leaf extract of J. gossypiifolia gave the highest repellent effect of 83.3% 
against both insects, while the least repelled was the bark of C. odorata against T. castaneum.  
The treatments were more repellent against S. zeamais as compared to T. castaneum. Studies by 
Ogendo et al. (2004) found similar repellency against maize weevil using leaf extracts from 
Lantana camara L. and Tephrosia vogeli (Hook). These findings indicate good potential of C. 
odorata and J. gossypiifolia for the use as repellent and toxic agents in the management of the 
maize weevil. Since plant derived pesticides are biodegradable and safer to higher animals, they 
offer a viable alternative to synthetic agrochemicals (Bouda et al., 2001; Soon-II et al., 2003). 
The degree of repellency to the two insects may depend on the habit of the insect species. 
Tribolium castaneum is always confined to closed habitats in the stored product environment 
while S. zeamais is often in close association with crops in the field, as well as in stores, and this 
tends to expose them to secondary compounds of botanicals. Furthermore, the results may be 
attributed to the presence of several secondary compounds from J. gossypiifolia leaves and its 
implication in the toxicity, including flavonoids (e.g. apigenin, isovitexin, vitexin) and 
diterpenoids (e.g. jatrophone) (Kupchan et al., 1970; Subramanian et al., 1971) that have both 
attractants and repellent properties. The repellent action increases the protectant potential of the 
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plants against storage insect pests since the treatment with high repellency reduced damage 
caused by the insects in stored grains. However, a detailed investigation of the effects of the 
individual constituent of the plant needs to be further studied. 
5.8 Toxicity of extracts to adult insects in treated grains 
The methanol and diethyl-ether extracts of C. odorata and J. gossypiifolia on the adult insects in 
treated grains after 4 days period increased the mortality and decreased the feeding activity of S. 
zeamais and T. castaneum with the highest concentration yielding the highest percentage 
mortality compared to the control. This could be due to the presence of the β-sitosterol, tanins 
and other saponins found in the leaves and bark of the plants which might act as antifeedants 
(GISD, 2006; Talukder, 2006). The leaf extracts protected the grain against damage than the 
bark. The lower protection observed in the bark extract could be attributed to the loss of toxic 
volatile secondary constituents during the drying and extraction process (Bekele et al., 1997). 
Asawalam et al. (2006) found that C. odorata leaf extracts caused 69% mortality of S. zeamais in 
treated grains. Stoll (2000) used 20% of lime to treat 1 kg of maize and was found to be very 
potent against S. zeamais in the treated maize. The test insecticide at the different concentrations 
was more toxic to S. zeamais than T. castaneum which further demonstrates that pirimiphos-
methyl, the active compound in Actellic was effective for the control of S. zeamais on maize 
grains at the recommended dose (Obeng-Ofori and Amiteye, 2005). 
5.9 Oviposition test 
The results obtained from the oviposition test using the acid fuschin egg-staining technique 
(Milner et al., 1950) detected that S. zeamais laid less number of eggs than T. castaneum. In a 
similar study by Ashford (1970) it was reported that a healthy Tribolium fertile female lays no 
egg in the first three days of adult life, and then lays egg at an increasing rate up to 18 per day. 
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The females of these insects laid eggs individually in small cavities chewed into grains and each 
cavity sealed and the egg protected by an egg-plug that was distinctly stained cherry-red. Once 
eggs were laid there was a high chance of survival irrespective of the further nutritional status of 
the grains (Frimpong, 2004). This detection of eggs on grains was done with the aim of testing if 
the insects actually laid eggs before treating the grains to determine the effect of extracts on the 
immature stages of the test insects. This method, however, revealed the efficacy of the extracts 
with low adult emergence though there were many eggs laid. 
 
5.10 Effect of extracts on immature stages of T. castaneum and S. zeamais 
The extracts of C. odorata and J. gossypiifolia reduced the number of adults of S. zeamais and T. 
castaneum that emerged in grains containing the egg and inhibited the development of larvae and 
pupae of both beetle species. Significant reductions in egg hatchability revealed the harmful 
effect of extracts of the plant species towards the eggs of the test insects. This observation is in 
agreement with that of Khanam et al. (2008) who reported that food treated with J. gossypiifolia 
leaf extract strongly inhibits the fecundity of T. castaneum compared with T. confusum. The leaf 
extracts of both plant species caused complete inhibition of emergence of the immature stages. 
The high activity of the leaf extract may confirm the presence of secondary compounds as 
reported by Taponjou et al. (2002). The high mortality induced by the leaf extracts of the plants 
indicates that they could be used for the control of grain storage insect pests. Similar 
investigations carried out by Okonkwo and Okoye (2006) revealed 50% mortality in adult S. 
zeamais and reduced adult emergence by Monodora myristica. The complete inhibition of the 
development of eggs and immature stages within grain kernels suggests the presence of ovicidal 
properties in the plant (Taponjou et al., 2002), and this increases the protectant potential of C. 
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odorata and J. gossypiifolia against insect damage in storage. 
5.11 Damage assessment 
The Thousand Grain Mass (TGM) method was used to assess percent weight loss on grain 
caused by S. zeamais and T. castaneum. Tribolium castaneum caused less damage to the stored 
grains throughout the storage period. Generally, beetle damage was significantly reduced in all 
treatments. The leaf extracts of both plant species significantly reduced damage more than the 
bark extracts. This is evidenced by the high repellency and low number of adult emergence in 
such treatments. The methanol extract of the bark of J. gossypiifolia was the least effective after 
the control in protecting grains from damage by S. zeamais and T. castaneum. The low percent 
weight losses reported occurred when the insects were feeding during the oviposition period 
prior to the treatment of the grains. Udo (2011) indicated that damage to grain by these insects 
was reduced in grains with treatments which exhibited high repellency to insects. The active 
compounds in these plants acted as deterrents and toxicants to the insects. These inhibited 
feeding on the grains by rendering them unattractive or unpalatable to the insects (Saxena et al., 
1988). At 37 days after infestation, the results showed that the differences in weight losss among 
the leaf extracts of the botanical pesticides were not significant for all the bioassays in this study 
even though each of the plant materials was generally less effective than Actellic applied to the 
grains. This resulted in the lowest percentage weight loss, perhaps on account of the fact that this 
product is a conventional synthetic insecticide specifically formulated with high insecticidal 
activities on stored product pests (Anon, 1993).  
Botanical pesticides represent an important component of integrated pest management (IPM) 
systems in traditional grain storage, as they are broad spectrum in action, based on local 
materials and potentially less expensive (Obeng-Ofori et al., 1997). Many are also safe to the 
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environment and harmless to man and other mammals (Talukder and Howse, 1995). However, 
farmers in the Awutu-Senya District were not using botanicals for grain protection, because they 
do not have the know-how to actually apply botanicals to protect their stored produce against 
pest infestation. Also, many of these non-chemical methods are slow acting and not standardized, 
their use are mainly dependent on experience and tradition (Delobel and Malonga, 1987; 
Belmain and Stevenson, 2001). In addition, the superiority in efficacy of synthetic compounds 
over non-chemical methods has been shown by recent studies. Okunade et al. (2002) reported 
that Pirimiphos-methyl was more potent against R.  dominica on sorghum in comparison to 12 
natural plant products. Similarly, Obeng-Ofori and Amiteye (2005) reported that only 
pirimiphos-methyl showed effective control of S. zeamais on stored maize grains when its 
efficacy was compared with products from three plant species. Synthetic chemicals, are often 
quick acting and persistent in the stored grain, thus ensuring long term protection. Most trials 
using botanicals are usually laboratory- based and of short duration. There is therefore, the need 
to build on farmers‘ experience and traditional methods in developing more cost-effective and 
sustainable storage-pest control strategies based on locally available botanicals for small-scale 
farmers in the Awutu-Senya District of Ghana. 
 
 
 
 
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CHAPTER SIX 
6.0 CONCLUSION AND RECOMMENDATIONS 
6.1 Conclusion 
Maize is the most important crop grown in the Awutu-Senya District of Ghana. Farmers store 
their maize for 7-8 months, generally to provide a food reserve, sale for better price as well as 
seed for future planting. However, maize storage conditions are inappropriate and farmers 
experience postharvest grain losses mainly due to insect attack. The maize weevil, S. zeamais 
was identified by farmers as a key pest of maize whose infestation starts in the field before 
harvest and extends throughout the storage period predisposing them to attack by the secondary 
pest, T. castaneum. The population of T. castaneum persisted throughout storage with the 
population increasing as storage duration was prolonged, making it a major pest. Owing to the 
economic importance attached to maize in Ghanaian agriculture there is the need to protect the 
crop against damage by the insecs during storage.  
It was observed that farmers in the district have been using pirimiphos-methyl (Actellic) as one 
of the pest control measures but was undermined by their low level of education in reading the 
labels for handling and application procedures and storage practices. Researchers and extension 
officers also need to educate maize farmers continuously in adopting suitable pest control 
methods since some of their activities can either promote pest outbreaks or reduce their 
infestation. 
The study has shown the bio-efficacies of the Siam weed, C. odorata and the Bellyache bush,  
J. gossypiifolia against S. zeamais and T. castaneum with insecticidal, antifeedant, ovicidal and 
repellent properties.  
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Extracts of dry leaf and bark of C. odorata and J. gossypiifolia were toxic to T. castaneum and S. 
zeamais when applied topically. 
The diethyl-ether leaf extracts of C. odorata and J. gossypiifolia repelled the insects, as well as 
reduced adult emergence in treated grains.  
Grains treated with the methanol and diethyl-ether leaf extracts of the two plant species reduced 
damage caused by S. zeamais and T. castaneum with resultant decrease in weight loss.  
Both solvents performed equally well on the average, but in terms of the effectiveness of the 
plant parts, the leaf extracts of both plants were more potent than the bark. 
All the laboratory bioassays showed that pirimiphos-methyl (Actellic) used at the current  
registered rate 4 ml/L (10 ppm) on maize was very effective against S. zeamais and T. castaneum 
adults, perhaps on account of the fact that this product is a conventional synthetic insecticide 
specifically formulated with high insecticidal activities on stored product pests. 
The results obtained from the study suggest good potential for the use of C. odorata and J. 
gossypiifolia in stored product pest management system, in view of the relative safety of the 
plants which are used to cure diseases like malaria and jaundice by drinking the boiled extract of 
C. odorata. In Ghana, the leaves of J. gossypiifolia are used as a purgative, and the leaf sap is 
applied to the tongue of babies to treat thrush and to inflamed tongues of adults. 
The results of this study have also established the scientific bases of the practice by farmers in 
northern Ghana in which the leaf of C. odorata is pounded and mixed into stored grain. The leaf 
extracts of C. odorata and J. gossypiifolia could therefore be used as a component of Integrated 
Pest Management in stored product protection if further field studies are undertaken. 
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6.2 Recommendations  
Based on the findings of the study, the following recommendations can be made:  
 Farmers should improve on postharvest practices to reduce losses of grain by harvesting 
early, sorting, drying and carrying out regular inspection of grains to be able to detect 
damage early; 
 Further studies should be carried out to assess postharvest losses attributed to insects in 
the traditional storage structures;  
 Researchers and extension officers need to involve maize farmers in finding and adopting 
suitable pest control methods since some of their activities can either promote pest 
outbreaks or reduce their infestation; 
 Extensive studies should be carried out on the biologically active compounds in C. 
odorata and J. gossypiifolia for the control of stored product pests to determine the 
precise mode of action of the active compounds; 
 Chemical residue analysis on maize and the effect of the extracts on non-target organisms 
should be carried out to enable its full incorporation into IPM practices; 
 Other solvents should be used for the extraction process to evaluate the efficacy in 
controlling insect pests; and  
 Studies should be carried out to determine the persistence of solvents on stored products 
and results should be validated in the field. 
 In so doing, a cheap readily available and environmentally friendly pest control agent can 
be developed for grain protection. 
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APPENDICES 
APPENDIX 1: 
Questionaire 
TOPIC: POSTHARVEST LOSSES AND EVALUATION OF THE BIOEFFICACY OF 
CHROMOLAENA ODORATA AND JATROPHA GOSSYPIIFOLIA AGAINST 
SITOPHILUS ZEAMAIS MOTSCH AND TRIBOLIUM CASTANEUM HERBST IN THE 
AWUTU-SENYA DISTRICT OF THE CENTRAL REGION OF GHANA 
This research is an academic exercise and all information given shall be used solely for the pur-
pose stated. All information given would be treated strictly confidential. 
Section A - General information on farmer  
1. Name of Interviewer: …………………………………………………….. 
2. Date of Interview: ……………................................................................... 
3. Place of Interview: ……………………………………………………….. 
4. Type of storage structure: ………………………………………………… 
5. Village status and tribe: …………………………………………………… 
6. Age:  20 and under  21 – 40  41 – 60  Over 60 
  ………….  ………. ………. ……… 
7. Sex of head of household   M F 
8. Number of wives / husbands ………………... 
9. Number of children / dependents ………… 
10. Age of children permanently resident: 
 0 – 7  8 – 14  15 – 18 
        ………          ……….           ………. 
11. How many people were you feeding regularly? ………………… 
12. Amount of cash spent on food per month? ……………………... 
13. How long have you been farming on your farm? ……………….. 
14. Where were you living before? District …….   Village ……. 
15. What type of storage is commonly used there? ……………………… 
16. Have you received any education?  
       Yes …………..  No ………….. 
17. If yes, indicate level. 
     Primary/Form …….. Secondary/Grade …….   Diploma ……   Others …… 
18. Farming experience (years) 
      10 and below 11-15       16-20 21 and above 
      ……………. …….        ……. …………… 
19. Do you do any other work other than farming? 
      Yes …….   No ……. 
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20. If yes, please specify?   ………………….. 
21. Indication of monthly income per household. 
      a. Cash in wages ………………… 
      b. Cash in salary ………………… 
      c. Pension allowance …………….. 
22. Type of farm animals in the house. 
a) Poultry ……….. 
b) Goat …………. 
c) Sheep ……….. 
d) Pig ………….. 
 
Section B – Crops and Storage 
1.  What crops did you grow? 
     Maize ………… 
     Cassava ……….. 
     Beans …………. 
       Others ………. 
 2.   Which of the food crops did you grow in most quantity? 
       Maize ……….. Cassava …………. Beans …………… Others ………….         
 3.   A. Were any of your crops mainly grown for the purpose of sale?  
             a. Yes …. b. No ….. 
       B.   If yes, specify ………………….. 
        Maize………. Cassava ………. Beans ………. Others ………. 
4.   Which crops did you store most? 
       Maize ……….  Cassava …………. Beans …………. Others ………….. 
5 Reason(s) for storage?  
    ……………………………………………………………………………………………… 
6. How did you decide what quantity of maize to grow? 
………………………………………………………………………………………………………
……………………………………………………………………………………………………… 
7.    Are there any conditions in which you would grow?  
       More maize ………………..  Less maize ……………………. 
8. What variety (ies) of maize did you grow? 
       Local …………..         Obaatanpa……………  Hybrid (once grown) …………….. 
9.  Has the quantity of maize you have grown changed in recent seasons? 
       No  More  Less 
       Local …………… ……………….. ……………… 
       Obaatanpa   ………..    ………………...          ………………. 
        Hybrid   …………… ………………… ……………… 
10.   Do you intend to change the quantity of maize you are growing? 
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         No                             More  Less 
              Local ……………….  …………. ……………….. 
           Obaatanpa ……………                     ………........               .……………….. 
           Hybrid ……………..             …………….           ……………….. 
11.      A. Have you received any training on when to harvest, how to dry and store maize? 
                 a. Yes ……………..   b. No ………………. 
           B. If yes, how often do you receive these visits? ……………………. 
12.      A. By what method did you plant your maize? 
           Broadcasting ……………..  Rows without spacing …………… 
           Rows with spacing ……….                Others …………….. 
           B. What tools did you use? 
           Hoe ……….      Plough ……….. Planter …………. Other ……………… 
13.      Did you use fertilizer or insecticide on your crops last season? 
             No     Fertilizer      Insecticide 
           Local ………………. ……………..  ………………… 
           Obaatanpa …………...          ………………             ………………… 
           Hybrid ………………. ……………..  ………………… 
14. What was the approximate date of harvest? ……………………. 
15. What was the approximate date of storage? …………………… 
16. Which variety of maize did you store? Local ………   Obaatanpa……. Hybrid …… 
17. How did you dry your maize? Natural drying  ……………..  
            Mechanical drying……………. 
18. a. Did you store your maize in the form of cobs or as shelled grains? 
 
         Cobs (with husks)    Cobs (without husks)         Shelled grains 
     …………………..   ……………………..                  ……………………. 
            b. If shelled, how did you shell it? 
           By hand …………….  Simple sheller ………………… Other ………………. 
19.      What quantity of maize did you put in store last season? ……………….. 
20. a. Did you keep any maize for seed? A. Yes ……………. B. No ………….. 
            b. If yes, i) What variety did you store? …………………. 
                ii) How did you store it?     ……………………..                     
               iii) How much did you store? …………..……….. 
21. Is there any condition that will let you store? 
      More maize ……………………………………........................................................................ 
      Less maize ……………………………………………………………………………………. 
22.  A. Did you buy any maize for seed? a. Yes …………………. b. No ………………. 
       B. If yes, i) What variety did you buy? ……………………… 
                          ii) From where did you obtain it?  ………….……… 
                         iii) What price did you buy it? ……………………… 
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Section C – Storage Facilities 
1. How many warehouses/stores did you have last season? ………………………………. 
2. Of what were these made (materials)?  
………………………………………………………………………………………………………
……………………………………………………………………………………… 
3. From where were these materials obtained?  
……………………………………………………………………………………………… 
4. What price did you buy it?  ………………………………………………………………. 
5. How old are your stores/warehouses? .................................................................................. 
6. For how many seasons have you used them? ……………………………………………... 
7. A. Did you spend any time repairing your stores? a. Yes …… b. No ………. 
            B. If yes, how frequent? …………………………………………………… 
8. Did you do anything else to your stores before filling it? a. Yes ….   No……  
9. A. Did you treat the maize before storage? a. Yes ……….b. No …………… 
            B. If yes, i) with what? ……………………………………………………………… 
                 ii) At what rate? ……………………………………………………………. 
10. A. Do you give the maize any further treatment whilst in store? a. Yes …. .b. No….. 
            B. If yes, what treatment did you give it? ...................................................................... 
11. Have you ever considered changing your method(s) of storage? a. Yes …...  b. No…….. 
12. If yes, what changes have you considered? ……..………………………………………… 
Section D – Usage of Stored Maize 
1. How often did you take maize out of your store? ……………………………………….. 
2. Did you take out a similar quantity each time? a. Yes ………… b. No ……………. 
3. From which part of the stack did you pick the maize? 
            Top ………….. Side door …………….. Others ……………… 
4. For what purpose did you use your maize? 
            Food …………….. 
            Feeding animals ………… 
            Seed …………….. 
            To sell ……………. 
            Gifts ……………. 
            Replace of loans ………….  
            Other purpose …………… 
Section E – Losses 
1.        A. Did the maize you stored show any signs of damage? a. Yes ………. b. No ……….           
           B. If yes, were some varieties of maize affected more than others? a. Yes …. b. No…….. 
 2.      What do you think caused this damage? 
          Insects ……… Moulds …………. Rats ……………… Others ………….. 
3.       What did you do to prevent these organisms from causing damage to your stored products?                     
………………………………………………………………………………………………… 
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4.       At what time of the year did most of the damage occur? …………………………………. 
5.      What did you do with the damaged maize?  
……………………………………………………………………………………………… 
6.      What proportion of your crop was affected?  
          i) In total ……………….. ii) By variety of maize …………………………….. 
7.      How much maize did you throw away? 
          i) In total ……………….. ii) By variety of maize ……………………………. 
8.      How much of your maize stored for seed did you throw away?  
…………………………………………………………………………………………….. 
9.      If your maize suffered less damage, would this alter the quantity that you 
                                                                 No              More      Less 
         a) Grow: Local  …………….  ………… ………… 
                                   Opaatanpa …………….  ………… ………… 
                                   Hybrid             …………….               …………        ………… 
         b) Store: Local  …………….  ………… ………… 
                                   Opaatanpa       ……………..              …………        ………… 
                                   Hybrid             …………….                …………        ………… 
Section F – Marketing 
1. What variety of maize did you sell?  ………………………………….. 
2. In what form did you sell it? Cob ……………… Shelled ………….. 
3. In what month did you sell your maize? ………………………………….. 
4. What was the reason that made you sell it at that time? .......................................  
5.      A) What grades of maize did you sell? 
        Good ……………  Slightly damaged ……………… Damaged.................       
         B) What proportion of the maize did you sell before storage? …………………………… 
6.     What price did you receive? ………………………………………. 
7.     A) Did these remain so for the rest of the season? a. Yes …………… b. No...........     
        B) If no, give details 
……………………………………………………………………………………………………… 
8.     A. Whom did you sell the maize to? 
       MoFA ……………….. Local traders …………….. Others …………………………… 
       B. What quantity did you sell to each people? 
       MoFA ………………..           Local traders …………….     Others ……………………... 
9. By what method did you transport your maize to the market? 
       Manually ………….  Road ……………….  Rail ………………….. 
10.  A. Did you buy any maize last season? a. Yes …………. b. No …………………. 
       B. If yes, for what purpose? …………………………………………………………….. 
11.  What variety? Local ……          Opaatanpa………..                Hybrid ………………… 
12.  What quantity? …………………………………………………………………………. 
13.  From where did you obtain it? ………………………………………………………….. 
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14.  When did you buy it? ………………………………………………………………….. 
15.  What price did you buy it? ………………………………………………………………. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 2: 
Analysis of variance for contact toxicity of methanol and diethyl-ether 
extracts of plants against S. zeamais and T. castaneum by topical application 
 
Analysis of variance for contact toxicity of 20% plant extracts on S. zeamais after 48 hours 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  15594.30  1732.70  72.95 <.001 
Residual 20  475.04  23.75     
Total 29  16069.33       
  
Analysis of variance for contact toxicity of 20% plant extracts on T. castaneum after 48 
hours  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  13669.33  1518.81  54.50 <.001 
Residual 20  557.40  27.87     
Total 29  14226.72       
  
  
   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 3: 
Analysis of variance for repellent effect of extracts on S. zeamais and 
T. castaneum 
 
Analysis of variance for repellent effect of C. odorata and J. gossypiifolia leaves and bark 
extracts on S. zeamais  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 8  1474.1  184.3  0.89  0.545 
Residual 18  3733.3  207.4     
Total 26  5207.4       
  
Analysis of variance for repellent effect of C. odorata and J. gossypiifolia leaves and bark 
extracts on T. castaneum  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 8  5466.7  683.3  1.81  0.141 
Residual 18  6800.0  377.8     
Total 26  12266.7       
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 4: 
Analysis of variance of the effect of extracts on adult insect in treated 
grains 
Analysis of variance of the effect of extracts on T. castaneum in treated grains on Day 4 at 
20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  10870.37  1207.82  49.92 <.001 
Residual 20  483.92  24.20     
Total 29  11354.29       
  
Analysis of variance of the effect of extracts on S. zeamais in treated grains on Day 4 at 
20% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  13777.91  1530.88  106.93 <.001 
Residual 20  286.33  14.32     
Total 29  14064.23       
  
 
Analysis of variance of the effect of extracts on T. castaneum in treated grains on Day 4 at 
50% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  11810.34  1312.26  71.20 <.001 
Residual 20  368.61  18.43     
Total 29  12178.94       
  
  
Analysis of variance of the effect of extracts on S. zeamais in treated grains on Day 4 at 
50% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  12343.56  1371.51  52.71 <.001 
Residual 20  520.38  26.02     
Total 29  12863.93       
  
 
Analysis of variance of the effect of extracts on T. castaneum in treated grains on Day 4 at 
100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  12964.17  1440.46  56.79 <.001 
Residual 20  507.28  25.36     
Total 29  13471.45       
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Analysis of variance of the effect of extracts on S. zeamais in treated grains on Day 4 at 
100% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  14141.63  1571.29  131.26 <.001 
Residual 20  239.42  11.97     
Total 29  14381.05       
 
 
Analysis of variance of the effect of diethyl-ether extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  125.51  125.51  4.04  0.115 
Residual 4  124.35  31.09     
Total 5  249.87       
  
 
 
Analysis of variance of the effect of methanol extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.00  0.00  0.00  1.000 
Residual 4  58.89  14.72     
Total 5  58.89       
  
  
Analysis of variance of the effect of diethyl-ether extract of C. odorata bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  5.55  5.55  0.50  0.519 
Residual 4  44.37  11.09     
Total 5  49.91       
  
   
Analysis of variance of the effect of methanol extract of C. odorata bark on adult S. zeamais 
and T. castaneum in treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.04  6.04  0.26  0.635 
Residual 4  91.69  22.92     
Total 5  97.73       
  
 
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Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia leaves on adult 
S. zeamais and T. castaneum in treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  29.445  29.445  4.00  0.116 
Residual 4  29.445  7.361     
Total 5  58.890       
 
 
Analysis of variance of the effect of methanol extract of J. gossypiifolia leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  7.36  7.36  0.50  0.519 
Residual 4  58.89  14.72     
Total 5  66.25       
  
 
 
Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration   
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.00  0.00  0.00  1.000 
Residual 4  44.37  11.09     
Total 5  44.37       
  
 
Analysis of variance of the effect of methanol extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.04  6.04  0.26  0.635 
Residual 4  91.69  22.92     
Total 5  97.73       
  
Analysis of variance of the effect of acetone control on adult S. zeamais and T. castaneum in 
treated grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.  0.     
Residual 4  0.  0.     
Total 5  0.       
    
 
 
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Analysis of variance of the effect of actellic on adult S. zeamais and T. castaneum in treated 
grains on Day 4 at 20% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  226.56  226.56  4.00  0.116 
Residual 4  226.56  56.64     
Total 5  453.13       
  
Analysis of variance of the effect of diethyl-ether extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  36.39  36.39  1.98  0.232 
Residual 4  73.51  18.38     
Total 5  109.90       
  
Analysis of variance of the effect of methanol extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  62.16  62.16  3.10  0.153 
Residual 4  80.28  20.07     
Total 5  142.45 
 
Analysis of variance of the effect of diethyl-ether extract of C. odorata bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.04  6.04  0.26  0.635 
Residual 4  91.69  22.92     
Total 5  97.73       
  
Analysis of variance of the effect of methanol extract of C. odorata bark on adult S. zeamais 
and T. castaneum in treated grains on Day 4 at 50% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.00  0.00  0.00  1.000 
Residual 4  48.33  12.08     
Total 5  48.33       
 
Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia leaves on adult 
S. zeamais and T. castaneum in treated grains on Day 4 at 50% concentration 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  11.02  11.02  1.00  0.374 
Residual 4  44.07  11.02     
Total 5  55.08      
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Analysis of variance of the effect of methanol extract of J. gossypiifolia leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  29.445  29.445  4.00  0.116 
Residual 4  29.445  7.361     
Total 5  58.890       
  
Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  5.55  5.55  0.50  0.519 
Residual 4  44.37  11.09     
Total 5  49.91       
 Analysis of variance of the effect of methanol extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 50% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.041  6.041  1.00  0.374 
Residual 4  24.165  6.041     
Total 5  30.206       
  
Analysis of variance of the effect of acetone control on adult S. zeamais and T. castaneum in 
treated grains on Day 4 at 50% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.  0.     
Residual 4  0.  0.     
Total 5  0.       
  
Analysis of variance of the effect of actellic on adult S. zeamais and T. castaneum in treated 
grains on Day 4 at 50% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  56.6  56.6  0.50  0.519 
Residual 4  453.1  113.3     
Total                                       5        509.8    
 
Analysis of variance of the effect of diethyl-ether extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.00  0.00  0.00  1.000 
Residual 4  88.13  22.03     
Total 5  88.13       
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 Analysis of variance of the effect of methanol extract of C. odorata leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.00  0.00  0.00  1.000 
Residual 4  88.13  22.03     
Total 5  88.13       
  
Analysis of variance of the effect of diethyl-ether extract of C. odorata bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.04  6.04  0.22  0.663 
Residual 4  109.73  27.43     
Total 
 5  115.77       
 Analysis of variance of the effect of methanol extract of C. odorata bark on adult S. 
zeamais and T.castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  24.165  24.165  4.00  0.116 
Residual 4  24.165  6.041     
Total 5  48.330       
 
Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia leaves on adult 
S. zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  11.02  11.02  0.50  0.519 
Residual 4  88.13  22.03     
Total 5  99.15       
  
Analysis of variance of the effect of methanol extract of J. gossypiifolia leaves on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  145.55  145.55  7.92  0.048 
Residual 4  73.51  18.38     
Total 5  219.06       
  
Analysis of variance of the effect of diethyl-ether extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  6.041  6.041  1.00  0.374 
Residual 4  24.165  6.041     
Total 5  30.206       
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 Analysis of variance of the effect of methanol extract of J. gossypiifolia bark on adult S. 
zeamais and T. castaneum in treated grains on Day 4 at 100% concentration  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  24.165  24.165  4.00  0.116 
Residual 4  24.165  6.041     
Total 5  48.330       
 
Analysis of variance of the effect of acetone control on adult S. zeamais and T. castaneum in 
treated grains on Day 4 at 100% concentration 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  0.  0.     
Residual 4  0.  0.     
Total 5  0.       
 Analysis of variance of the effect of actellic on adult S. zeamais and T. castaneum in treated 
grains on Day 4 at 100% concentration 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Days 1  226.56  226.56  4.00  0.116 
Residual 4  226.56  56.64     
Total 5  453.13       
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 5: 
Analysis of variance for effect of extracts of C. odorata and J.gossypiifolia on 
immature stages of T. castaneum and S. zeamais 
 
Analysis of variance for effect of extracts of C.odorata and J.gossypiifolia on eggs of 
T.castaneum 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  580.7000  64.5222  71.69 <.001 
Residual 20  18.0000  0.9000     
Total 29  598.7000       
  
Analysis of variance for effect of extracts of C. odorata and J. gossypiifolia on eggs of S. 
zeamais 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  609.4667  67.7185  96.74 <.001 
Residual 20  14.0000  0.7000     
Total 29  623.4667       
  
Analysis of variance for effect of extracts of C. odorata and J. gossypiifolia on larvae of T. 
castaneum  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  512.0000  56.8889  106.67 <.001 
Residual 20  10.6667  0.5333     
Total 29  522.6667       
  
Analysis of variance for effect of extracts of C. odorata and J. gossypiifolia on larvae of S. 
zeamais 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  641.4667  71.2741  118.79 <.001 
Residual 20  12.0000  0.6000     
Total 29  653.4667       
  
Analysis of variance for effect of extracts of C. odorata and J. gossypiifolia on pupae of T. 
castaneum  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  654.6667  72.7407  90.93 <.001 
Residual 20  16.0000  0.8000     
Total 29  670.6667       
  
 
 
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Analysis of variance for effect of extracts of C. odorata and J. gossypiifolia on pupae of S. 
zeamais 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  575.4667  63.9407  91.34 <.001 
Residual 20  14.0000  0.7000     
Total 29  589.4667       
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 6: 
Analysis of variance for the effect of extracts of C.odorata and J.gossypiifolia 
on grain damage by S. zeamais and T. castaneum 
 
 
Analysis of variance for the effect of extracts of C. odorata and J.gossypiifolia on grain 
damage on S. zeamais egg  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  95.3603  10.5956  31.50 <.001 
Residual 20  6.7267  0.3363     
Total 29  102.0869       
      
Analysis of variance for the effect of extracts of C. odorata and J. gossypiifolia on grain 
damage on S. zeamais larva  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  88.0805  9.7867  67.06 <.001 
Residual 20  2.9189  0.1459     
Total 29  90.9993       
  
Analysis of variance for the effect of extracts of C. odorata and J. gossypiifolia on grain 
damage on T. castaneum egg  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  39.0468  4.3385  13.61 <.001 
Residual 20  6.3762  0.3188     
Total 29  45.4230       
  
Analysis of variance for the effect of extracts of C. odorata and J. gossypiifolia on grain 
damage on T. castaneum larva  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  14.1503  1.5723  15.06 <.001 
Residual 20  2.0876  0.1044     
Total 29  16.2379       
    
 
 
 
 
 
 
 
 
 
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APPENDIX 7: 
Analysis of variance for the effect of oviposition on damage caused by 
S. zeamais and T. castaneum on stored grains using the acid fuschin solution 
egg staining technique 
Analysis of variance for the effect of oviposition on damage caused by S. zeamais on stored 
grains using the acid fuschin solution egg staining technique 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  2299.2  255.5  1.39  0.256 
Residual 20  3668.9  183.4     
Total 29  5968.1       
  
Analysis of variance for the effect of oviposition on damage caused by T. castaneum on 
stored grains using the acid fuschin solution egg staining technique  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  2237.9  248.7  2.16  0.073 
Residual 20  2302.5  115.1     
Total 29  4540.4       
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDIX 8: 
Analysis of variance for the effect of infestation level on damage caused by 
S. zeamais and T. castaneum on stored grains using grain dissection 
Analysis of variance for the effect of infestation level on damage caused by S. zeamais larva 
on stored grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  2628.51  292.06  14.03 <.001 
Residual 20  416.36  20.82     
Total 29  3044.88       
  
Analysis of variance for the effect of infestation level on damage caused by S. zeamais pupa 
on stored grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  1932.90  214.77  16.26 <.001 
Residual 20  264.13  13.21     
Total 29  2197.03       
  
 
Analysis of variance for the effect of infestation level on damage caused by T. castaneum 
larva on stored grains using grain dissection 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  930.01  103.33  4.95  0.001 
Residual 20  417.75  20.89     
Total 29  1347.76       
  
Analysis of variance for the effect of infestation level on damage caused by T. castaneum 
pupa on stored grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Treatment 9  2401.23  266.80  13.57 <.001 
Residual 20  393.15  19.66     
Total 29  2794.38       
  
Analysis of variance for the effect of infestation level of diethyl-ether extracts of C. odorata 
leaves on damage caused by T. castaneum and S. zeamais larvae on stored grains using 
grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  50.85  50.85  1.09  0.356 
Residual 4  187.20  46.80     
Total 5  238.05       
  
 
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Analysis of variance for the effect of infestation level of methanol extracts of C. odorata 
leaves on damage caused by T. castaneum and S. zeamais larvae on stored grains using 
grain dissection 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  177.33  177.33  12.15  0.025 
Residual 4  58.38  14.59     
Total 5  235.71       
  
 
Analysis of variance for the effect of infestation level of diethyl-ether extracts of C. odorata 
bark on damage caused by T. castaneum and S. zeamais larvae on stored grains using grain 
dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  13.260  13.260  1.50  0.287 
Residual 4  35.291  8.823     
Total 5  48.551       
  
 
Analysis of variance for the effect of infestation level of methanol extracts of C. odorata 
bark on damage caused by T. castaneum and S. zeamais larvae on stored grains using grain 
dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  6.04  6.04  0.21  0.669 
Residual 4  114.26  28.56     
Total 5  120.30       
  
Analysis of variance for the effect of infestation level of diethyl-ether extracts of J. 
gossypiifolia bark on damage caused by T. castaneum and S. zeamais larvae on stored 
grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  0.00  0.00  0.00  1.000 
Residual 4  87.85  21.96     
Total 5  87.85       
  
Analysis of variance for the effect of infestation level of methanol extracts of J. gossypiifolia 
bark on damage caused by T. castaneum and S. zeamais larvae on stored grains using grain 
dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  91.16  91.16  6.42  0.064 
Residual 4  56.83  14.21     
Total 5  148.00       
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Analysis of variance for the effect of infestation level of diethyl-ether extracts of J. 
gossypiifolia leaves on damage caused by T. castaneum and S. zeamais larvae on stored 
grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  95.36  95.36  6.30  0.066 
Residual 4  60.56  15.14     
Total 5  155.92       
 
Analysis of variance for the effect of infestation level of methanol extracts of J. gossypiifolia 
leaves on damage caused by T. castaneum and S. zeamais larvae on stored grains using 
grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  6.55  6.55  0.42  0.551 
Residual 4  62.05  15.51     
Total 5  68.61       
 
 
Analysis of variance for the effect of infestation level of actellic on damage caused by T. 
castaneum and S. zeamais larvae on stored grains using grain dissection 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  76.54  76.54  3.46  0.136 
Residual 4  88.51  22.13     
Total 5  165.05 
 
Analysis of variance for the effect of infestation level of acetone control on damage caused 
by T. castaneum and S. zeamais larvae on stored grains using grain dissection 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  39.24  39.24  1.89  0.241 
Residual 4  83.17  20.79     
Total 5  122.41       
  
Analysis of variance for the effect of infestation level of diethyl-ether extracts of C. odorata 
leaves on damage caused by T. castaneum and S. zeamais pupae on stored grains using 
grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  51.910  51.910  5.97  0.071 
Residual 4  34.763  8.691     
Total 5  86.674       
 
 
 
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Analysis of variance for the effect of infestation level of methanol extracts of C. odorata 
leaves on damage caused by T. castaneum and S. zeamais pupae on stored grains using 
grain dissection 
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  50.268  50.268  5.98  0.071 
Residual 4  33.635  8.409     
Total 5  83.903       
 
Analysis of variance for the effect of infestation level of diethyl-ether extracts of C. odorata 
bark on damage caused by T. castaneum and S. zeamais pupae on stored grains using grain 
dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  0.00  0.00  0.00  1.000 
Residual 4  144.08  36.02     
Total 5  144.08       
  
Analysis of variance for the effect of infestation level of methanol extracts of C. odorata 
bark on damage caused by T. castaneum and S. zeamais pupae on stored grains using grain 
dissection 
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  0.00  0.00  0.00  0.986 
Residual 4  46.93  11.73     
Total 5  46.93       
  
Analysis of variance for the effect of infestation level of diethyl-ether extracts of J. 
gossypiifolia bark on damage caused by T. castaneum and S. zeamais pupae on stored 
grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  68.45  68.45  3.78  0.124 
Residual 4  72.39  18.10     
Total 5  140.84       
         
Analysis of variance for the effect of infestation level of methanol extracts of J. gossypiifolia 
bark on damage caused by T. castaneum and S. zeamais pupae on stored grains using grain 
dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  1.401  1.401  0.24  0.648 
Residual 4  23.008  5.752     
Total 5  24.409       
  
 
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Analysis of variance for the effect of infestation level of diethyl-ether extracts of J. 
gossypiifolia leaves on damage caused by T. castaneum and S. zeamais pupae on stored 
grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  0.000  0.000  0.00  1.000 
Residual 4  11.685  2.921     
Total 5  11.685       
 
 
Analysis of variance for the effect of infestation level of methanol extracts of J.gossypiifolia 
leaves on damage caused by T. castaneum and S. zeamais pupae on stored grains using 
grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  5.842  5.842  4.00  0.116 
Residual 4  5.842  1.461     
Total 5  11.685       
   
Analysis of variance for the effect of infestation level of acetone control on damage caused 
by T. castaneum and S. zeamais pupae on stored grains using grain dissection  
 
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  155.71  155.71  6.08  0.069 
Residual 4  102.46  25.61     
Total 5  258.16       
  
Analysis of variance for the effect of infestation level of actellic on damage caused by T. 
castaneum and S. zeamais pupae on stored grains using grain dissection  
  
Source of variation d.f. s.s. m.s. v.r. F pr. 
Stage 1  0.41  0.41  0.01  0.929 
Residual 4  182.49  45.62     
Total 5  182.90       
  
 
 
 
 
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