ON- FARM EVALUATION OF CANDLEWOOD ZANTHOXYLUM 

XANTHOXYLOIDES (LAM.) ON TWO STORED PRODUCT 

PESTS.

BY
CHARLES KWESI KOOMSON (B.Sc. HONS., ZOOLOGY)

A THESIS SUBMITTED TO THE AFRICAN REGIONAL POSTGRADUATE 
PROGRAMME IN INSECT SCIENCE (ARPPIS), UNIVERSITY OF GHANA, LEGON IN 
PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER 

-' OF PHILOSOPHY DEGREE IN ENTOMOLOGY.

INSECT SCIENCE PROGRAMME *

UNIVERSITY OF GHANA 

LEGON 

AUGUST 2003.

* JOINT INTERFACULTY INTERNATIONAL PROGRAMME FOR THE TRAINING OF 
ENTOMOLOGISTS IN WEST AFRICA

COLLABORATING FACULTIES : AGRICULTURE AND SCIENCE >

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C 371174
3 KS 3

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DEDICATION

To my siblings: Payin and Kakra Manful

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I do hereby declare that, except for references to works of other researchers 

which have fully been duly cited, this work is the result of my own original 

research, carried out at the Food Security Laboratory, Zoology Department, 

University of Ghana, Legon and the University of Ghana Farms, Legon, under the 

supervision of Dr. Ebenezer Oduro Owusu and Prof. J. N. Ayertey that this 

research neither in whole nor in part has been presented for another degree 

elsewhere.

DECLARATION

CHARLES KWESI KOOMSON 
(STUDENT)

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ABSTRACT

The biological activity of dry, ground plant parts (dust) and tablets of 

Zanthoxylum xanthoxyloides (Lam.) was assessed in both the laboratory and on 

the field against the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: 

Curculionidae) and the cowpea weevil, Callosobruchus maculatus (F.) 

(Coleoptera: Bruchidae).

Dry ground leaves, bark and roots were prepared in various proportions of 60% 

leaves and 40% roots; 70% leaves and 30% roots; 80% leaves and 20% roots; 

90% leaves and 10% roots; 60% leaves and 40% bark; 70% leaves and 30% 

bark; 80% leaves and 20% bark; 90% leaves and 10% bark, as well as 100% 

leaves, 100% bark and 100% roots. These proportions were mixed with 5 kg of 

grains at 5% (wt/wt) concentration to assess contact toxicity, grain protection, 

effect on eggs and immature stages and persistency.

The biological activity of Z xanthoxyloides was also accessed using tablets made 

from different concentrations of 2.2ml leaves and 1.8ml roots; 2.4ml leaves and 

1.6ml roots; 2.6ml leaves and 1.4ml roots; 2.8ml leaves and 1,2ml roots; 2.2ml 

leaves and 1.8ml bark; 2.4ml leaves and 1.6ml bark; 2.6ml leaves and 1.4ml 

bark and 2.8ml leaves and 1.2ml bark. Five tablets of each of the different 

concentrations were mixed with 5 kg of grains to assess toxicity or grain 

protection by fumigation, effect on eggs and immature stages persistency and 

repellency.

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The effective combinations of dry ground dusts were 60% leaves and 40% roots; 

70% leaves and 30% roots; 60% leaves and 40% bark and 70% leaves and 

30% bark. These significantly (P<0.001) induced over 68 % mortality of both 

species of insects, provided about 96% protection to the grains, inhibited the 

development of eggs and immature stages and were persistent for 2 months.

The effective tablet formulations were from concentrations of 2.2 ml: 1.8ml (v/v) 

leaves: roots; 2.4 ml: 1.6 ml (v/v) leaves: roots; 2.2 ml: 1.8ml (v/v) leaves: bark 

and 2.4 ml: 1.6ml (v/v) leaves: bark. These induced about 50% mortality, 

offered about 95% protection to the grains and evoked repellent actions against 

both insects. There was however, a rapid loss of activity after 7 days following 

treatment, irrespective of the dosage applied.

Z  xanthoxyloides, which is relatively safe to mammals because it is used for the 

treatment of ailments like tooth aches, stomach aches, leprous ulceration, and 

ulcers, syphilitic sores, fever, post-delivery pains while the leaves are fed to 

ruminants could be prepared into effective dry ground dust proportions as well 

as tablets for resource-poor farmers to protect their grains against some stored 

product pests.

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ACKNOWLEDGEMENT

My greatest thanks go to God for helping me to carry out this research 

successfully. I wish to express my profound gratitude to my parents, especially 

my mother for the pain and responsibility they took in educating me this far. I 

render my sincere appreciation and gratitude to my supervisors Prof. J.N. 

Ayertey, Coordinator of the African Regional Postgraduate Programme in Insect 

Science and Dean of Graduate Studies, University of Ghana, Legon and Dr. 

Ebenezer Oduro Owusu of the Zoology Department, University of Ghana, Legon, 

for all their assistance, advice, constructive criticisms and encouragement in the 

supervision of this research work.

I am very much grateful to Dr. Daniel Obeng-Ofori, Head of Crop Science 

Department, University of Ghana, Legon, for the numerous assistance, literature 

and encouragement he gave me at various stages of this work. I acknowledge 

with thanks the financial support, information and encouragement of Mr. John 

Manful of the Food Research Institute (C.S.I.R.) Accra, for this research work.

I am very much indebted to Dr. Akuamoah of the Chemistry Department, 

University of Ghana, Mr. David Asiedu and Mr. Amoakoh, both of the 

Microbiology Department, Food Research Institute (C.S.I.R.) Accra, for providing 

literature, equipments, chemicals and assistance in the preparation of the

Zanthoxylum xanthoxyloides tablets.

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Immense thanks go to Kuukua, Fiifi, Cynthia, Tufour, Mavis, Lydia, Jemima, 

Kufour, Naana, Vida, Jennifer as well as my course mates: Dickson, Telemacus, 

Sakyi, Ken, Gadzama, Bonaventure, Duna and Nkem for their support and 

encouragements at various stages of this research.

Finally, I wish to express my warmest gratitude to Miss Sandra Ama Nyame 

Takyiwaa Osam for her company, prayers, advice and encouragement 

throughout the execution of this research.

.<C< 0t~' s

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TABLE OF CONTENTS

Page

DEDICATION "

DECLARATION "i

ABSTRACT iv

ACKNOWLEDGEMENT v!

LIST OF TABLES Xiii

LIST OF FIGURES AND PLATES xiv

CHAPTER 1

1.0 GENERAL INTRODUCTION 1 

CHAPTER 2

2.0 LITERATURE REVIEW 5

2.1 Overview 5

2.2 Storage losses 8

2.3 The maize weevil Sitophilus zeamais Motsch.

(Coleoptera: Curculionidae) 10

2.3.1 Taxonomy and Description 10

2.3.2 Distribution and Dispersal 10

2.3.3 Factors affecting pre-harvest infestation of maize 11

2.3.3.1 Maturity of maize grains 11

2.3.3.2 Moisture content of maize 13

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2.3.3.3 Husk cover 12

2.3.4 Losses caused 12

2.3.5 Life history and behaviour 13

2.3.6 Control 13

2.3.6.1 Chemical control 13

2.3.6 .2 Biological control 14

2.3.6 .3 Traditional and cultural control 15

2.4 The cowpea weevil Callosobruchus maculatus (F.)

(Coleoptera: Bruchidae) 16

2.4.1 Taxonomy and Description 16

2.4.2 Distribution and Dispersal 16

2.4.3 Infestation 17

2.4.4 Losses caused 17

2.4.5 Life history and behaviour 17

2.4.6 Control 18

2.4.6.1 Chemical control 18

2.4.6 .2 Biological control 18

2.4.6 .3 Traditional and cultural control 18

2.5 Integrated Management of C. maculatus and S. zeamais 19

2.6 Other pests of stored maize and cowpea 20

2.7 The candlewood Zanthoxylum xanthoxyloides Lam. 21

2.7.1 Taxonomy, Distribution and Ecology 21

2.7.2 Utilization of Z xanthoxyloides 22

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CHAPTER 3 29

3.0 MATERIALS AND METHODS 29

3.1 Grains used 29

3.2 Culturing of insects 29

3.2.1 5. zeamais 29

3.2.2 C. maculatus 30

3.3 Collection and preparation of plant materials 30

3.3.1 Proportions of dust used 31

3.3.2 Preparation of tablets 32

3.4 On-farm storage facility 34

3.5 Tests of dusts and tablets 35

3.5.1 Persistency test 35

3.5.2 Effect of the dust on eggs 36

3.5.3 Effect of the dust on larvae 36

3.5.4 Effect of the dust on pupae 36

3.5.5 Repellency test of tablets 37

3.6 Mortality assessment 38

3.7 Data analysis 38

CHAPTER 4

4.0 RESULTS 48

4.1 Yield of extracts 48

4.2 Toxicity of various proportions of dust 48

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4.3 Toxicity of various concentrations of tablets 49

4.4 Damage assessment of dust 53

4.5 Damage assessment of tablets 53

4.6 Effect of Z  xanthoxyloides dust and on eggs

and immature stages 56

4.7 Repellency bioassay of tablets 59

4.8 Persistency test of dust 61

4.9 Persistency test of tablets 61

5.0 DISCUSSION

5.1 Toxicity of dust 65

5.2 Antifeedant effect Z  xanthoxyloides dust 66

5.3 Effect of Z  xanthoxyloides dust on eggs and immature stages 66

5.4 Persistency of Z  xanthoxyloides dust 67

5.5 Toxicity of Z. xanthoxyloides tablets 68

5.6 Antifeedant effect of Z  xanthoxyloides tablets 69

5.7 Repellency of Z. xanthoxyloides tablets 69

5.8 Persistency of Z  xanthoxyloides tablets 70

CHAPTER 6

6.0 CONCLUTION AND RECOMMENDATIONS 72

REFERENCES 74

APPENDIX 89

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LIST OF TABLES

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8a.

Vernacular names of Zanthoxylum xanthoxyloldes 

Secondary plant metabolites in Z. xanthoxyloides ■

Typical analysis of agar

Preliminary investigation of the most toxic dust 

proportion of Zanthoxylum xanthoxyloides

Preliminary investigation of the most toxic

Z. xanthoxyloides tablets

Effect of Z  xanthoxyloides dust on damage caused by 

Sitophilus zeamais and Callosobruchus maculatus

Effect of Z xanthoxyloides tablets on damage caused by 

Sitophilus zeamais and Callosobruchus maculatus

Mean numbers of S. zeamais and C. maculatus that 

emerged from grains treated with Z. xanthoxyloides 

dust after different days of adult removal in the laboratory

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Table 8 b. Mean numbers of 5. zeamais and C. maculatus that 

emerged from grains treated with Z  xanthoxyloides 

dust after different days of adult removal on the field 58

Table 9 Mean percentage repellency (pr) values for the

Z  xanthoxyloides tablets against SitophiIus zeamais and 

Callosobruchus maculatus in a choice test 60

Table 10a Persistency test of Z xanthoxyloides dust in the lab. 62

Table 10b Persistency test of Z  xanthoxyloides dust on the field 63

Table 11 Persistency test of Z. xanthoxyloides tablets in the lab. 64

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Page

Fig. 1 Percentage yield of extracts from different plant parts

of Zanthoxylum xanthoxyloides 50

Plate 1 Sitophilus zeamais 25

Plate 2a Rostrum of female Sitophilus zeamais 26

Plate 2b Rostrum of male Sitophilus zeamais 26

Plate 3 Callosobruchus maculatus 27

Plate 4 Candlewood Zanthoxylum xanthoxyloides 28

Plate 5 Sitophilus zeamais being reared on maize 40

Plate 6 Callosobruchus maculatus being reared on cowpea 41

Plate 7 Zanthoxylum xanthoxyloides dust 42

Plate 8 Controlled experimental room 43

LIST OF FIGURES AND PLATES

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Plate 9 Rotary evaporator 44

Plate 10 Air-tight containers used in preparing Z  xanthoxyloides

tablets 45

Plate 11 Zanthoxylum xanthoxyloides tablets 46

Plate 12 On-farm storage facility (wooden crib) 47

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CHAPTER ONE

1.0 GENERAL INTRODUCTION

Post-harvest food loss is one of the major problems contributing to world food 

insecurity. Prior to the early 1970's, efforts to increase world food supplies largely 

concentrated on increasing production but after the early 1970's there was 

developing awareness that total food availability could be improved through the 

reduction of post-harvest losses (Boxall, 1986). FAO production figures in 1980 

shows that 1,627.125 million metric tones of major grains were produced worldwide. 

Using the often-quoted conservative minimum overall food grain loss figures of 10% 

the total loss to mankind of cereal grains was estimated to be 162.7125 million tones 

(Ayertey, 1986).

Grains form the most important staple for the growing population in the tropics; with 

cereals and legumes providing important sources of carbohydrate and protein 

respectively (Niber, 1994). Grains are durable products, usually stored to provide a 

food reserve and seed for planting. However, grains in storage are damaged by 

several species of insect pests (Anon, 1958) leading to loss in weight and seed 

quality, especially germination ability (Richter, 1993). In West Africa, Sitophilus 

zeamais Mots. (Coleoptera :Curculionidae) has been reported to be the major pest of 

maize Zea mays and Caliosobruchus maculatus (F.) (Coleoptera: Bruchidae)* the 

major pest of cowpea, Vigna ungulculata (L.) Walp. (Dick, 1998) causing between 

20-30% of stored grains (Hill, 1998).

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Attempts at reducing infestation have concentrated on the use of synthetic 

insecticides. About 90% of those insecticides are imported with a high debt burden, 

due to high unfavourable exchange rates. Medium to large-scale farmers continue 

to depend greatly on pesticides. Thus, their usage has increased over the past 10- 

15 years due to the frequent association of insects, micro-organisms and weeds with 

crops (Poswal and Akpa, 1991).

However, the poor storage facilities of traditional farmers in developing countries are 

unsuitable for conventional chemical control, because most storage facilities are not 

air tight enough for fumigation and some are open to reinfestation by insects and 

this calls for repeated applications, leading to over use of insecticides. The 

widespread use and overuse of synthetic chemicals have led to serious problems, 

including the development of insect resistant strains to insecticides, toxic residues on 

stored grains, health hazards to grain handlers, food poisoning and environmental 

pollution among others (Champ and Dyte, 1976; Zettler and Coperus, 1980; White, 

1985). Consequently, the need to find alternative candidate materials that are 

readily available, effective, affordable, less poisonous and less detrimental to the 

environment, has turned the attention of Entomologists and Toxicologists, to 

research into medicinal plants grown locally (Tierto, 1994).

Plants are rich sources of compounds that have insecticidal properties (Schmutterer, 

1995; Bekele et a l 1997 Olaifa et al. 1987; Obeng-Ofori etal. 1998; Owusu, 2000). 

Seeds of Melia volkensii M. Guerke (Rombold, 1994), Ocimum species Willd. 

(Kumar, 1987), Adzadirachta indica A, Juss (Addae-Mensah, 1998), Cassia sophera

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Oliv. (Koomson, 2000) as well as many others have been successfully used to 

control insect pests.

Candlewood, Zanthoxytum xanthoxyloides (Lam.) (Rutacesae) is effective against 

several stored product pests. Dry plant materials of the roots, stems, leaves and 

seeds have been shown to be effective against' S. zeamais, C. maculatus and 

Tribolium castaneum Herbst, under laboratory conditions (Osafo, 1998; Udo, 2000). 

Extracts of the roots and stem proved most effective, giving 100% protection to 

maize and cowpea and completely inhibited progeny production and development of 

eggs and immature stages of 5. zemias and C. maculatus within grains. The extracts 

also evoked a strong repellent action against T. castaneum but were moderately 

repellent against C. maculatus and S. zeamais (Udo, 2000).

According to Udo (2000), the bark and roots were most effective giving 100% 

mortality after 72 hours, with the leaves giving only about 64% mortality after 72 

hours. But if the root and bark were to be used solely, it would mean destroying the 

plants. This is because the root is responsible for the absorption of water and 

mineral salts for photosynthesis and the bark protects the plant against mechanical 

injury as well as insect, fungal and bacterial attacks. The current aspect of the 

research was thus aimed at combining the leaves with the roots and bark in different 

proportions to determine how best to maximize the use of the leaves and minimize 

the use of the roots and bark of candlewood to control S. zeamais and C. maculatus.

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But the questions that remain to be answered are:

1. Candlewood is effective in the laboratory, but will it work in the field?

2. What proportions of leaves, stem and roots would be effective in the field?

3. What is the effect of the effective proportions on the various life stages of S.

zeamais and C. maculatus

4. How persistent are the active components?

5. Which formulation of Candlewood is most effective?

This research therefore sought to answer these questions and fill some of the gaps 

in our knowledge on the use of candlewood products to control insect pests. The 

main objective of this research was therefore to find out ways in which parts of 

Candlewood can be used to achieve maximum control of insects in the field.

Specific objectives were:

1. To determine how best the leaves, bark and roots of candlewood can be put into 

various proportions to improve efficacy.

2. To determine efficacy in an on-farm storage facility

3. To determine effect on the various life stages of S. zeamais and C. maculatus.

4. To determine persistency in an on-farm storage facility.

5. To determine the effective formulations of candlewood that can be used against 

S. zeamais and C. maculatus.

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CHAPTER TWO

2.0 REVIEW OF LITERATURE

2.1 Overview

The battle against pests has been an age-long one, to improve man's welfare and 

ensure food security. Various practices aimed at managing pest situations through 

an integrated approach, which advocates for a combination of methods such as 

cultural, biological, genetic and plant resistance, as well as minimal use of chemical

insecticides, have been widely adopted.

The use of botanicals for pest control is an age-long traditional practice, but was 

neglected at the advent of synthetic insecticides. With the production of Dichloro- 

diphenyl-trichloroethane (DDT) in 1941, the world saw nothing but an "ideal 

insecticide" capable of "dealing brutally" with pest organisms in their vast forms and 

numbers (Kumar, 1987). Thus, the discovery of DDT initially, though to be the 

universal synthetic panacea against insect attack, proved after prolonged usage to 

be disastrous (Jacobson, 1989). Most of these synthetic insecticides are toxic to 

predacious insects and leave toxic residues in food, soil and water bodies, making 

them unsafe (Rembold, 1994). Other problems associated with indiscriminate use of 

synthetic pesticides are the destruction of natural enemies of certain insect pests, 

development of resistant strains of pest species and the high cost of treatment. 

Carson (1962) warned of the dangers of synthetic insecticides and signaled DDT's 

practical elimination of living organisms due to high persistence, toxicity, 

biomagnifications, tendency to cause malignancy, development of resistance in pest

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organisms and environmental degradation. Considering the above dangers of 

synthetic chemical insecticides, attention was once again turned to phytochemicals 

(van Emden, 1989)

Besides the treatment of grain, the application of residual sprays to grain storage 

facilities is an integral part of good pest control practice (Williams et al , 1982; Giga 

and Canhao, 1992). Insecticides, when properly used, will continue to play an 

important role in reducing storage losses due to insect pest activities (Menn, 1983; 

Redlinger et a!., 1988). Among small-scale farmers in the developing countries, 

insecticides available on the market are rather expensive and are often not economic 

to use. The use of conventional synthetic chemicals by farmers therefore is not 

sustainable and the greatest challenge in stored products protection is to find 

alternative methods for protecting commodities (Golob, 1997). In West Africa, 

farmers are resorting to using phosphine to control insect pests. Evidence from 

Ghana indicates that the use of phosphine is being carried out with no consideration 

to safety or efficacy. Users have no training and together with their suppliers, usually 

small-scale wholesalers and retailers, • are putting people at risk and greatly 

increasing the chance of resistance developing (Golob, 1997).

There is a growing interest in the use of natural products to control insects (Cutler, 

1988; Hedin, 1990). In stored products, this interest is driven by a need for 

alternatives to traditional fumigants and residual insecticides that are becoming 

ineffective due to resistance in insect populations or are no longer available due to 

regulatory controls or are too expensive (Civerolo eta!., 1993).

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The plant origin is a vast storehouse of chemicals and offers a wealth of compounds 

known for their medicinal and insecticidal properties. Natural plant compounds used 

in the control of insect pests are as varied as the plants from which they have been 

isolated (Dongdem, 1997). Plants in the families Meliaceae, Labitae, Asteracea, 

Canellaceas; have been studied extensively for their insecticidal properties 

(Jacobson, 1989).

To protect extinction, plants have been waging biochemical warfare for thousands of 

years against insects and herbivores (Alkofahi et a l, 1989). Perhaps many plant 

species, which failed to develop such protective "secondary metabolites", were 

consumed and made extinct. Thus, plant resistance, one of the main factors of 

survival of wild plants, can be attributed to several chemical mechanisms. These 

include the action of toxic substances, hormone mimics, anti-hormones, antifeedants 

and repellents (Marinibettolo, 1983).

Although there is increasing research into botanicals used for the protection of 

stored food, these efforts are still inadequate (Dales, 1996). There are difficulties in 

recommending botanicals as a replacement for chemical insecticides because 

efficacy levels of botanicals often vary among storage pests, application methods, 

and stored products (Cobbinah e t al., 1999).

Protection of stored products generally involves mixing grains with protectants 

derived from local plants (Hassanali et al., 1990). Botanical insecticides tend to have 

broad-spectrum activity, are relatively specific in their mode of action and easy to

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process and use (McDonald et al., 1970; Talukder and Howse, 1994). They are also 

safe to higher animals and the environment (Anon., 1991). Resource-poor farmers 

and small-scale industries can often easily produce botanical insecticides at the farm 

level.

2.2 Storage Losses

Insect pest damage to stored grain results in major economic losses to farmers 

throughout the world (Obeng-Ofori et a l, 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). Damage to stored produce cannot be retrieved, thus leading to 

direct monetary loss, estimated at more than 500 million dollars in the U.S. annually 

(Oldroyd, 1960).

In the developing countries, food grain production often falls below demand as a 

result of post-harvest losses caused by pests, poor transportation, handling and 

processing. The prevailing high temperatures and humid conditions also favour the 

rapid growth, development and proliferation of storage pests and fungal diseases 

that cause considerable damage in storage (Mutlu and Hountondji, 1990). In Africa, 

where subsistence grain production supports majority of the population, grain losses 

caused by storage insect pests such as Sltophilus zeamais and Callosobruchus 

maculatus can be critical (Golob and Tyler, 1994).

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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 tons respectively are 

lost to insects (Owusu-Akyaw, 1991).

In the Sahel region, post harvest losses are significant for bagged maize and 

sorghum because of damage caused by insects and rodents (Alzouma, 1990). On 

the other hand, beetles 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 susceptible to attack by 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 

pesticides use.

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2.3 S. ZEAMAIS

2.3.1 TAXONOMY AND DESCRIPTION OF S. ZEAMAIS.

The maize weevil S. zeamais Motschulsky (Plate 1) is a member of a triumvirate 

species in the family Curculionidae, sub-family Calandrinae, genus Sitophilus (Hill, 

1983). The body size ranges from 2.4 to 2.5 mm. Body colour ranges from light 

brown to black with four reddish orange elongate spots on the elytra. The antennae 

have eight segments and are often carried in extended position when the insect is 

walking. They have metathoracic flight wings (Dobie, 1991). Both males and females 

have characteristic rostrum but the latter could be distinguished from the former by 

the shape and texture of the rostrum, which is smoother, longer, and more curved in 

the female (Plate 2a) than in the male (Plate 2b) (Kiritani, 1965).

2.3.2 DISTRIBUTION AND DISPERSAL OF S. ZEAMAIS.

S. zeamais has a cosmopolitan distribution throughout the tropics and sub-tropics 

(Southgate et a l, 1956). In the field, they are unevenly distributed. Dix and All 

(1985) carried out intensive sampling of maize fields and reported a clumped 

distribution of both weevil population and of weevil-infested ears. They suggested 

that clumping is a response to the release of aggregation pheromone by the first 

male to colonize the maize plants (there was a male-to-female ratio of 1.6 : 1.0 in 

the weevil population collected from cobs sampled'two months before harvest). In 

most of the fields studied, the weevil-infested ears were in a linear pattern across 

the field. This may again have resulted from down-wind dispersal of aggregation 

pheromone from colonizing males. A marked 'edge of field' effect had been noted in 

some studies of field infestation of S. zeamais. Numbers of adult weevils dropped

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dramatically 15-30 m from the field border (Giles and Ashman, 1971). Surveys of a 

number of fields indicated that, even at the margins, the distribution of insects was 

uneven and was generally determined by the direction and proximity of infested 

maize stores to the growing crop(Giles and Ashman, 1971). Chesnut (1972) studied 

the dispersal of S. zeamais from a source of infestation using adults marked with a 

fine paint spray. No marked adults were found on the cobs located more than 400 m 

from the release point.

2.3.3 FACTORS AFFECTING PRE-HARVEST INFESTATION OF ZEA MAIS BY

S. ZEAMAIS.

2.3.3.1 Maturity of maize grains

The ability of S. zeamais and other storage pests to infest growing maize plants is 

influenced by factors related to the maturity of the grains. In Kenya, Giles and 

Ashman (1971), artificially pollinated maize plants of several varieties, covered the 

developing ears with cloth bags, and then introduced marked adult S. zeamais into 

the bags at different times after pollination. They observed that the developing 

period decreased as the crops matured.

2.3.3.2 Moisture content of maize

Infestation is high when the moisture content is well above 30%. As the moisture 

content drops towards the end of the growing season, only damaged grains remain 

susceptible to attack by the pests. In southwest Nigeria, Markham (1981) examined 

cobs from a field of maize 3 weeks before the dry-season harvest (late November). 

He found no evidence of 5. zeamais infestation of the grains, which had mean

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moisture content of 57%. Three weeks later, 45% of the harvested cobs were 

infested by S. zeamais, the moisture content of the grain had by then dropped to 

30%. At the wet-season harvest, mean grain moisture was again 30%. However, 

only 28% of the cobs were infested.

2.3.3.3 Husk cover

Another important factor affecting pre-harvest infestation of maize by storage 

species is the degree to which the maize grains are exposed because of incomplete 

husk cover. In Kenya, Giles and Ashman (1971) examined maize ears 2 months 

before harvest. On the average, 7% were infested with S. zeamais. When the cobs 

were divided into categories depending on the degree of protection afforded by the 

husk, only 1% of the cobs with complete husk cover were infested, whereas 20% of 

those in which grains could be observed at the tip were infested. Exposing cobs by 

opening the sheaths at the tips greatly increased the number of weevils caught in 

the suction trap placed in a maize field (Taylor, 1971). Taylor concluded that 

exposed ears induced flight activity of S. zeamais and thus increased the probability 

that cobs with short husks would become infested.

2.3.4 LOSSES CAUSED BY S. ZEAMAIS

The pest destroys about 8-10% of the world's stored grains (Hill, 1983). The larvae 

cause the greatest damage because they spend their entire life within the grain by 

eating voraciously to prepare for the quiescent pupa stage (Dobie e t al , 1991).

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2.3.5 LIFE HISTORY AND BEHAVIOUR OF S, ZEAMAIS.

Hill (1981) reported that the eggs are laid throughout the life of the insect. Fifty per 

cent may be laid in the first 4-5 weeks. The eggs are laid individually in small 

cavities chewed into cereal grains by the female and each cavity is sealed and 

protected by a gelatinous waxy secretion usually referred to as "egg plug" produced 

by the female. Oviposition rates are at maximum at 70% relative humidity, 20-30 °C 

and above 10% of moisture content (Dobie, et al, 1991). The eggs hatch into 

apodous (legless) larvae in 6-7 days after oviposition and begin to feed inside the 

grain; excavating a tunnel as it develops (Dobie, et al, 1991). The larvae go through 

4 instar stages and take 21 days to change into the pupa. The adult develops in 

about 35 days. The total developmental period ranges from 35 days under optimal 

conditions of 25°C and 70% relative humidity to over 110 days in unfavourable 

conditions (Haines, 1991).

2.3.6 CONTROL OF S. ZEAMAIS.

2.3.6.1 Chemical control

The use of insecticides to control or reduce storage losses to food crops has become 

increasingly common. In southern United States, applications of insecticides on 

growing maize plants, 3 weeks and 7 weeks before harvest, reduced by 90% the 

number of ears infested with the predominant pest, Sitophilus zeamais 'in 

comparison with untreated control plants (Evans, 1985). In Zambia, Hindmarsh and 

MacDonald (1980) reported that admixture of malathion 1% dust, tetrachlorvinphos 

3% dust, pirimiphos-methyl 2% dust or fenitrothion 1% dust (2ppm) reduced the 

percentage of shelled grains with visible insect damage to less than 5%, over a 7 -

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month storage period. However, trials in West Africa carried out to test the use of 

insecticides with improved crib designs, permethrim dust applied to dehusked cobs 

proved more effective than lindane, bromophos, malathion or pirimiphos-methyl but 

all treatments resulted in more than 5% damage to grains after 5 months in store 

(FAO, 1985). Deltamethrin has also been found to be very effective in controlling S. 

zeamais (Evans, 1985).

2.3.6.2 Biological control

A number of species of natural enemies are associated with the indigenous pest 

found in African maize stores. In an experimental maize crib in Nigeria, distributions 

of two commonest hymenopteran parasites present, Chaetospila elegans and 

Cerocephalia dinoderi (both Pteromalidae) were positively correlated with that of S. 

zeamais and they prey very well on S. zeamais (Markham, 1981). Pteromalid, 

Anisopteromabus calandrae (Howard), Lariophagus distinguendus (Foster) are also 

common parasites of 5. zeamais (Hill, 1983). Dobie (1974) investigated inherent 

resistance to attack by S. zeamais of a large number of genotypes held at Centro 

International de Majoramiento de Maiz y Trigo (CIMMYT)'s maize seed bank in 

Mexico. He found out that selection of new, high-yielding cultivars with the 'opaque- 

2' gene in their genome (conferring to a high lysine and tryptophan content, as well 

as soft pericarp) is likely to increase the susceptibility of stored maize to S. zeamais.

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2.3,6.3 Traditional and cultural control of S. zeamais.

In India, Su (1977) reported that powdered rhizoi'nes of turmeric, Curcuma tonga 

mixed with maize repel S. zeamais from eating the maize. Turmeric contains 

pungent, odoriferous oils and oleoresins but the repellent components are turmerone 

and ar-turmerone (Su e t  al., 1982). Azadirachta indica, which contains Triterpenoid 

azadirachtin and other related compounds, is reported to have repellent actions 

against 5. zeamais (Schumutterer, 1995). In Ghana, storage containers made from 

large woven baskets, set on poles and covered with a thatched roof reduces field 

infestation of 5. zeamais on harvested maize crops (Kumar, 1987). Ground and 

whole pepper fruits have been used to protect stored products from insect damage 

(Mould, 1973). Su (1977) found black pepper to be a safe and promising source of 

naturally occurring insecticide for the control of S. zeamais by reducing oviposition 

and adult emergence. Heating and smoking had been used to control S. zeamais in 

households in Ghana and is achieved by heating to 64 °C for 10 min and cooling at 

18 °C for 4 days (Kumar, 1987). Control of some insect pests is achieved by 

following the principle of growing crops at a time when pests are absent or their 

numbers are not high. As a result, the most susceptible stage of a crop's 

development coincides with the time when the pest is least abundant (Kumar, 

1987). Endrody-Younga (1968) carried out an extensive study on maize infestation 

in Central Ashanti, Ghana. He concluded that maize planted at the start of the first 

rainy season (February through April, when pest numbers are very low), without 

fertilizer use, insecticide application or irrigation gave higher yield than the average 

given by FAO (above 1000-kg ha"1) for the country as a whole.

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2.4 C. MACULATUS

2.4.1 TAXONOMY AND DESCRIPTION OF C. MACULATUS

(Co!eoptera:Bruchidae)

The cowpea weevil C. macuiatus (Plate 3) belongs to the sub-family Bruchinae (Hill, 

1983). The body size ranges from 1.9 mm to 2.0 mm, has a brownish colour and a 

pair of emarginated eyes (Hill, 1983). The insect has strait elytra, which is not able 

to cover the posterior part of the abdomen completely. The antennae have ten 

segments but are not capable of being flexed backwards when walking (Dobie, et 

al., 1991). They have a pair of distinct ridges (inner and outer) on the ventral side 

and each ridge bears a tooth near the apical end. The inner tooth is triangular and 

equal to (or slightly longer than) the outer tooth (Booker, 1967). The female can be 

distinguished from the male by a more smoother and curving antennal segments 

and strong markings on the elytra consisting of two large lateral dark patches, mid 

way along the elytra and smaller patches at the anterior and posterior ends, leaving 

a paler brown cross shaped area covering the rest of the body (Dobie et al, 1991).

2.4.2 DISTRIBUTION AND DISPERSAL OF C. MACULATUS

C. maculatus has a cosmopolitan distribution throughout the tropics and sub-tropics 

(Southgate et al., 1957). In the field, they are unevenly distributed and could be 

aggregated which result from the release of aggregation pheromones from

colonizing males or scattered mainly along the margins (Dobie, e t al., 1991).

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2.4.3 INFESTATION OF C. MACULATUS

Field infestation takes place when the grains are matured usually 2-3 weeks before 

harvest of cowpea and also when the grain moisture is well above 30% (Dobie et 

al, 1991). According to Southgate (1978), pre-harvest infestation is increased when 

the grains are exposed as a result of incomplete shell cover.

2.4.4 LOSSES CAUSED BY C. MACULATUS

The pest destroys 6-8% of the world's stored cowpea (Hill, 1983). The larvae cause 

the greatest damage because they can attack very .hard grain testa and spend their 

entire life eating voraciously within the grain to prepare for the quiescent pupa and 

feedless larvae stages (Dobie et a!., 1991).

2.4.5 LIFE HISTORY AND BEHAVIOUR OF C. MACULATUS

The adult beetle, which does not feed on stored products, is very short-lived (usually 

no more than 12 days under optimum conditions) (Hill, 1983). The female can lay 

as many as 115 small, grey and inconspicuous eggs firmly glued, to the surface of 

the host seed, mostly cowpea (Dobie et al., 1991). Oviposition rates are at 

maximum at temperatures ranging between 30-35 °C and as the eggs are laid, they 

are firmly glued to the surface of the host seed (Booker, 1967). Smooth seeded 

varieties are suitable for oviposition than rough seeded varieties (Haines, 1991). The 

eggs hatch into scarabaeiform (Oshaped and fat) larvae and bites through the base 

of the eggs, into the cotyledons. There they feed voraciously within and excavate a 

chamber as they grow (Dobie et. al , 1991). The larvae develop into the pupae after 

20 days and the adult normally emerges after 7 days at optimum conditions (Hill,

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1983). The total developmental period ranges from 28 days under optimal conditions 

of 32°C and 90% relative humidity to 35 days in unfavourable conditions and about 

six or seven generations in a year are usual (Hill, 1983).

2.4.6 CONTROL OF C. MACULATUS

2.4.6.1 Chemical control

According to Hill (1983), fumigation with methyl bromide is an effective method of 

control. However, following an outbreak in Costa Rica in 1974, a more 

comprehensive investigation of insecticide efficacy against the pest was undertaken. 

It was found that permethrim, fenvalerate and cypermethrin were very effective in 

controlling the pest (Dick, 1988).

2.4.6.2 Biological control

C. maculatus in commonly parasitised by Grapholitha glycinivorella (Hill, 1983). In 

an experimental bean crip, Southgate (1978) found out that two common parasitic 

Pteromalid Hymenoptera attack the larvae of C. maculatus. These two parasites are 

Anisopteromalus calartdrae (Howard) and Dinarmus basalis {Rondani).

2.4.6.3 TRADITIONAL AND CULTURAL CONTROL OF C. MACULATUS

Ash and sand are some of the local materials used in the control of storage pests in 

South and West Africa for the protection of cowpea (Poswal and Akpa, 1991). The 

use of mixture of dried sand and dung ash was capable of causing 80% mortality of 

C. maculatus (Poswal and Akpa, 1991). Ash and sand have no insecticidal properties 

but fill the space between grains, restricting the movements of adults for egg laying.

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They also act as desiccants thus decreasing infestation levels. An ancient method of 

storing cowpea seeds practiced by the Sayawa people of Bauchi State of Nigeria is 

by smoking. Cowpea pods are suspended in the kitchen and the smoke completely 

prevents storage pests from attacking the seed (Poswal and Akpa, 1991). They also 

observed that a low concentration of powder of Piper guineenses significantly 

reduced oviposition and adult emergence, while oviposition was completely 

suppressed at concentrations of 42%. Neem extracts have repellent, antifeedant 

and insecticidal properties, which effectively control C. maculatus. Drying of the 

cowpea in direct sunlight in Ghana reduces the moisture content and appears to be 

largely effective in minimizing infestation by C. maculatus (Obeng-Ofori, 1998).

2,5 INTEGRATED MANAGEMENT OF C. MACULATUS AND S. ZEAMAIS.

This is an al! inclusive term that describes man's continued efforts to control 

populations of pest species at levels that are advantageous to his well being 

(Anonymous, 1972). It involves maximum reliance on natural pest population 

controls along with a combination of techniques such as biological, chemical, 

traditional and other control methods that lead to the suppression of pests (Kumar, 

1987). Dick (1988) reports that the judicious use of contact insecticides such as 

permethrin and fenvalerate, pheromone-baited traps such as (Z)-9-tetradecenyl and 

(Z)-9, (E)-12-tetradecadienyl acetate for monitoring, and possibly for control, 

thermal disinfestations by solar drying, and the use of biological control insecticides 

such as neemol and pyrithrum (botanicals), Chaetospiia elegans and Grapholitha 

glycinivorella, as the control techniques in both cowpea and maize farms can 

produce the greatest results in controlling C. maculatus and S. zeamais.

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2.6 OTHER PESTS OF STORED MIAIZE AND COWPEA

Stored maize and cowpea are also attacked by the several insect pests such as 

Sitophilus oryzae (L), Rhizopertha dominica (Jr.), Cathartus quandricollis (Guer), 

Gnatocerus maxillosus (F.); Tribolium castaneum (Herbst), Palorus subdepressus 

(Woll), P. ratzburgii (Deg), Araecerus fasciculatus (Deg.), Oryzaephilus mercator 

(Fauv.), Brachypeplus pilosellus Murray, Sitotroga cerealella (Oliv.)/ Prostephanus 

truncates (Horn), Bruchidius atrolineatus (Pic.), Piezotrachelus varium (Wagner), P. 

ratzburgii (Wissm.), Tenebroides mauritanicus (L), Plodia interpuctella (Hubn.), 

Lasioderma serricorne (F.) (Obeng- Ofori, 1998).

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2.7 THE CANDLEWOOD, ZANTHOXYLUM XANTHOXYLOIDES

2.7.1 Taxonomy, distribution and ecology

The candlewood, Zanthoxylurn xanthoxyloides Lam., (Plate 4), belongs to the 

family Rutaceae, which contains about 1700 species placed in 161 genera. It is a 

shrub that grows to a small tree up to 1.25 m high and 0.13 m girth (Irvine, 

1961). The trunk is gray with large woody thorns. The large woody thorns falls 

later and the trunk becomes covered with thick corky and woody thorns only on 

older branches. The bark is acid to taste initially and rapidly becomes hot with 

peppermint aftertaste (Hawthorne, 1990). The leaves when crushed give off an 

aromatic spicy scent (Irvine, 1961). The seeds are widely used as spices in local 

cuisines in Asia (Katzer, 2000) that is why the closely related Asian species Z. 

pipertitum is called Sichuan pepper. American Zanthoxylurn spices have not yet 

been put to culinary use (Katzer, 2000). The twigs are very thorny and the 

leaves are pinnate, with three and four pairs of shinning, glabrous, aromatic 

leaflets that are elliptic to oblong, obtuse and entire with rachis of 10 X 3075 cm 

and recurred thorns. The midribs are also thorny (Irvine, 1961). The plant 

flowers between December to March. The flowers are small, numerous and white 

with dense terminal panicles. The fruits are brown and often split into two to 

produce one shinny blue-black seed that has a spicy taste (Irvine, 1961).

The tree is widely grown in closed and savanna forest habits, and sometimes in 

coastal thickets (Nakanishi and Suzuki, 1998). It also thrives well on drier and 

well-drained soils (Neumann and MullerHaude, 1999).

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Local names mostly reflect the potential of the species in this genus (Table 1). 

Most importantly, in Hausa, Z. xanthoyloides is called 'Fasa Kwari' which means 

'Kills insects' (Gazama, pers. Comm) (Table 1). The plant is very medicinal, being 

used to treat many ailments (Dalziel, 1937; Keharo and Bouquet, 1950 and 

Irvine, 1961).

Several plant metabolites have been identified in Z  xanthoxyloides (Table 2)

The insecticidal property of candlewood was first reported against C. maculatus 

(Escoubas et al, 1994; Ogunwolu and Idowu, 1994; Ogunwolu and Odunlami, 

1996). Following this, promising results were obtained in a trial against several 

stored product pests (Osafo, 1998). Based on these results, Udo (2000) set out 

to investigate the efficiency of candlewood against three stored product pests:

S. zeamais, C. maculatus and T. castaneum., This study showed that the bark 

and roots were the most effective plant parts, against the above-mentioned 

pests providing up to 100% protection of cowpea and maize.

2.7.2 UTILIZATION OF Z  XANTHOXYLOIDES

The seeds of Z  xanthoxyloides are used for making necklaces in Senegal (Irvine, 

1961). The ripe seeds serve as pepper and for flavouring butter, while the dried 

and pulverised leaves are sometimes used in West Africa to flavour food in Cote 

d'Ivoire (Dalziel, 1937). The leaves are fed to sheep in certain Ga villages in 

Ghana (Irvine, 1961). The wood is yellow, hard, durable and resistant to termites

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and as such used for building purposes. It makes excellent firewood as it 

contains an inflammable resin. The young shoots are used as chewing sticks and 

as bitters.

The medicinal values of the plant have long been known as various parts of the 

plants have long been used to treat many ailments. The pounded roots, 

sometimes mixed with guinea grass or capsicum peppers, are used to control 

stomachaches. The powdered roots are used in French West Africa against 

ulcers, sores, including syphilitic sores, and leprous ulceration (Kerharo and 

Bouquet, 1950). The roots are boiled with cereals and used for the treatment of 

fever, as vermifuge and with other drugs to treat paralysis. Pulverized roots, 

sometimes mixed with other hot species are, commonly placed in carious teeth 

as a remedy for toothache. The bark can also be made into poultice and applied 

against rheumatism and swellings (Dalziel, 1937).

In Ghana, post-delivery pains are relieved by an extract of the root in rum 

(Irvine, 1961). The plant has antiseptic and analgesic properties. It has been 

reported that the bark decoction is used as an enema for an unspecified purpose 

and the juice of the bark for eye diseases, especially purulent conjunctivitis 

(Irvine, 1961).

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TABLE 1

Vernacular names of Z. xanthoxyloides

Tribe Local name Source

Twi Okanto, Yea, Bebun Tufour, pers. comm.

Fanti Kanfu Kuukua, pers. comm.

Ga Haatsho Lydia, pers. comm.

Ewe Xe, Xeti Micheal,pers. comm.

Nzema Ayenle, Ayinle Fiifi, pers. comm.

Hausa Faskori, Fasa Kwari Gadzama, pers comm

Table 2

Secondary Plant metabolites in Z  xanthoxyloides. 

Secondary Metabolite Source

Alkaloids

Atarine

Fagaridine

Pseudo-fagarol

Tannin & Saponin

Zantocylol

Pellitorine

Fagaramide

Henry (1949)

Henry (1949)

Irvine (1961)

Irvine (1961)

Irvine (1961)

Elujoba & Nagels (1985) 

Ginesta et. al  (1994) 

Ginesta et a! (1994)

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PLATE 1 SITOPHILUS ZEAMAIS ADULT

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PLATE 2a ROSTRUM OF FEMALE SITOPHILUS ZEAMAIS

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PLATE 3 CALIOSOBRUCHUS MACULA TUS ADULT

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PLATE 4 LEAVES AND THORNY WOODY STEMS OF CANDLEWOOD 
ZANTHOXYLUM XANTHOXYLOIDES

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CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 GRAINS

Maize and cowpea used for this investigation were bought from the Madina 

Market in Accra. The grains were sterilized in an oven at 40°C for six hours and 

then kept in the freezer at -4°C till when they were used, to prevent any 

reinfestation (Owusu, pers. comm.).

The quantity to be used was removed and kept in the rearing room where the 

environment was controlled for one week under culture conditions of 2.8± 2°C, 

68 ± 2% RH and 12L:12D photo regime. This was to allow the grains to 

equilibrate. (Weaver et al., 1994; Osafo, 1998; Udo 2000).

3.2 CULTURING OF INSECTS

3.2.1 S. ZEAMAIS

Insects were collected from a stock culture kept in a laboratory at the 

Department of Zoology of the University of Ghana.

About 500 insects were introduced into 500g of pre-equilibrated grains in a kilner 

jar (Plate 5) and covered with muslin doth held in place by rubber band. The set 

up was left in the controlled environment room at 28± 2°C, 68% R.H and 12L: 

12D photo regime (Weaver, 1994; Osafo, 1998; Udo, 2000).

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After two weeks of oviposition, the adults were sieved out with an impact test 

sieve. This was to enable the production of progeny that was to be used to 

establish a main culture with subsequent reculturing after every eight weeks, so 

that insects of about the same age were always available for the various 

experiments.

3.2.2 C. MACULATUS

C. maculatus were collected from stock cultures kept at the same laboratory at 

the Department of Zoology of the University of Ghana.

About 500 insects were introduced into 500 g of sterilized and pre-equilibrated 

cowpea in a kilner jar (Plate 6) covered with muslin cloth and held in place with 

rubber band. The cultures were left undisturbed in the insectary, maintained at 

28± 2°C, 68 ±2% R.H and 12L: 12D photo regime. The adults were removed 

after two weeks, by which time they had laid eggs. Progeny that emerged were 

sieved and used for subcultures for the various experiments.

3.3 COLLECTION AND PREPARATION OF PLANT MATERIALS

Leaves, roots and bark of Z  xanthoxyloides were collected from the University of 

Ghana farm at Legon, Accra. The materials were dried in a room and pounded 

into smaller pieces using a mortar and pestle. The poundered pieces were 

further milled into powder using a milling machine at the Nutrition and Food 

Science Department, University of Ghana. The powdered materials were then

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sieved with an impact test sieve with mesh size of 710U to obtain fine powder for 

the different tests (Plate 7).

3.3.1 PROPORTIONS

The powdered materials were used as dusts mixed with grains at 5%

concentrations (wt/wt) (Udo, 2000).

The proportions were in the form of mixtures of:
(0-

Leaves (%) Roots (%)
60 40
70 30
80 20
90 10
100 0
0 100

(ii).
Leaves (%) Bark (%)
60 40
70 30
80 20
90 10
0 100

These were tested at 5% concentrations (wt/wt) against 40 mixed sex adults of 

S. zeamais and C. maculatus in 5 kg. of maize and cowpea respectively in jute 

sacks in the laboratory (Plate 8). Each proportion was replicated five times and 

mortality was observed daily for one week. The observation was done by sieving 

out each of the five replicates for each treatment using an impact test sieve and 

then counting the number of dead and alive insects. Insects were considered

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dead if they did not respond to three probings of a blunt forceps. Loss 

assessment of the grains was determined using the F.A.O. (1985) count and 

weigh method:

% Wt loss = (UNd -DNu) x 100 
U(Nd + Nu)

Where U = weight of undamaged grains

D = weight of damaged grains

Nd = No. of damaged grains

Nu = No. of undamaged grains

The most effective proportions were then tested in an on-farm storage facility at 

the same concentration where mortality and loss due to insect damage were 

assessed weekly for one month.

The proportions that proved most effective in the' field were further prepared in 

suitable formulations for application. In this case, the materials were applied as 

tablets.

3.3.2 PREPARATION O f TABLETS

The tablets were prepared at the Zoology Department of the University of 

Ghana. Roots, bark and leaves of Z  xanthoxyloides were chopped into smaller 

pieces and 250 g of each of these parts was mixed with 70% methanol in a 500- 

litre glass jar. The mixture was left in darkness for three days. The methanol

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solution was evaporated using a rotary evaporator (Plate 9) to remove the 

methanol at 30°C-40°C with rotary speed of 3-6 rpm for 8 hours according to 

the procedure of Godefroot et al. (1981). The extracts were stored in a 

refrigerator at 8°C (Ofuya and Okuku, 1994).

Some 3% of agar was prepared as follows: 3 g of agar was boiled with 100ml of 

distilled water in a water bath for 30 minutes. Based on concentrations used by 

Udo (2000) and also concentrations used in earlier trials carried out in the 

laboratory, the extracts were mixed up in proportions of:

(i) leaves and roots, in ratios of (2.2ml leaves to 1.8ml roots), (2.4ml leaves 

to 1.6ml roots), (2.6ml leaves to 1.4ml roots) and (2.8ml leaves to

1.2ml roots).

(ii) leaves and bark, in ratios of (2.2ml leaves to 1.8ml bark), (2.4ml leaves 

to 1.6ml bark), (2.6ml leaves to 1.4ml bark) and (2.8ml leaves to 

1.2ml bark).

The mixtures were then poured in small airtight containers with dimensions of 

3.5cm in diameter and 3.0cm in height. One millilitre of the hot agar solution 

was mixed with each of the extracts in the airtight containers. The mixtures 

were then left to cool down at room temperature into solid tablets with the 

containers tightly closed (Plate 10). The weight of the tablet was

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10.0 g; the weight of the extracts in each tablet was 8.0 g and the weight of 

the agar in each tablet was 2.0g. The tablet had a diameter of 3.5cm and a 

width of 1cm (Plate 11).

The type of agar used was LAM M™ Agar No. 1 MC 2 manufactured by the 

International Diagnostic Group pic. It had a weight of 500g with the typical 

analysis as presented in Table 3. Five tablets of the various concentrations 

were placed at the bottom of the sacks containing the grains and then left in 

the controlled experimental room (Plate 8). Mortality was observed daily for 

one week to determine the effective tablet concentration.

3.4 ON- FARM STORAGE FACILITY.

This is a ventilated crib made of wooden strips of about three meters tall and 

divided into four compartments of one meter, wide. It is situated on the 

University of Ghana farm, Legon. (Plate 12). The following tests described earlier 

were carried out in the crib: persistency test, testing of effective proportions of 

the dust and the tablets, testing for the effects of the dust and the tablets on the 

eggs and immature stages of the insects, and experiments to determine the 

protection ability of the dust and the tablets on the grains against insect attack.

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3.5 TESTS OF DUST AND TABLETS

3.5.1 PERSISTENCY TEST

Five kilograms of maize and cowpea were each admixed with the effective 

powdered dusts at 5% concentrations wt/wt. This was placed in a 35 cm by 45 

cm jute bags and placed in the laboratory and in the crib.

Each treatment was replicated five times in the laboratory and in the crib. Two 

other sets of replicates of both the maize and cowpea treatments were also 

placed in the laboratory and in the crib. 20 S. zeamais adults were put into one 

set of replicates of the maize treatments and 20 C. maculatus adults were also 

put into one set of replicates of the cowpea treatments. These were left in the 

laboratory and in the crib for one month after which the insects were sieved out 

and the number of dead and alive insects recorded. Twenty new S. zeamais and 

C. maculatus adults were put in the second set of replicates of the maize and 

cowpea treatments respectively and the insects were sieved out after another 

one month. The numbers of dead and alive insects were also recorded. The 

same procedure was repeated for the third set of replicates of both the maize 

and cowpea treatments alter the second month, until such period that the 

treatments were no longer effective in controlling the insects. The period was 

recorded.

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The same procedure was used to test the persistency of the tablets but in this 

case five tablets were put in each jute bag and the testing period was done 

weekly for three weeks in the laboratory.

3.5.2 EFFECT OF THE DUST ON EGGS.

Five kilograms each of the equilibrated maize and cowpea placed in the jute sacs 

were infested with 100 adults of S. zeamais and C. maculatus respectively to 

allow for egg laying. The parent adults were removed after seven days. The 

grains were then treated with the effective powdered proportions the following 

day. Each treatment was replicated three times. No treatment was added to the 

control. Adults emerging subsequently were sieved and counted after four weeks 

(Su, 1977). This was done both in the laboratory and on the field.

3.5.3 EFFECT OF THE DUST ON LARVAE

Five kilograms each of the equilibrated maize and cowpea placed in the jute sacs 

were infested with 100 adults of S. zeamais and C. maculatus respectively to 

allow for egg laying. The parent adults were removed after seven days. The 

grains were then treated with the effective powdered dust proportions after one 

week. Each treatment was replicated three times. No treatment was added to 

the control. Adults emerging subsequently were sieved and counted after four 

weeks (Su, 1977). This was done both in the laboratory and on the field.

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3.5.4 EFFECT OF THE DUST ON PUPAE

Five kilograms each of the equilibrated maize and cowpea placed in the jute sacs 

were infested with 100 adults of S. zeamais and C. maculatus respectively to 

allow for egg laying. The parent adults were removed after seven days. The 

grains were then treated with the effective powdered dust proportions after 

twenty-eight days in the case of S. zeamais and after twenty days in the case of 

C. maculatus. Each treatment was replicated three times. No treatment was 

added to the control. Adults emerging subsequently were sieved and counted 

after four weeks (Su, 1977). This was done both in the laboratory and on the 

field.

3.5.5 REPELLENCY TEST OF TABLETS

P.epellency test was assessed in a choice bioassay method using grains treated 

with the Z  xanthoxyloides tablets. Ten grammes of the grains were treated with 

the tablets and a control of another 10 g of grains was placed on a clean filter 

paper adjacent to each other. This was replicated twice. Some 10 adult S. 

zeamais and C. maculatus were introduced onto each experimental set 

separately. The number of insects present on the control (Nc) and treated (Nt) 

grains were recorded after one hour. Percentage repellency (PR) was computed

PR = Nc - Nt x 100 
Nc + Nt

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The data were analysed using ANOVA after transformation into arcsine values. 

Ali negative PR values were treated as zero (Obeng-Ofori e t al, 1997).

3.6 MORTALITY ASSESSMENT

Each replicate of the various treatments was sieved out and the number of dead 

and alive insects counted. Percentage mortality was calculated from the formula:

Number of dead insects X 100%
Total number of insects

The percentage mortalities were corrected using the Abbott's (1925) formula:

P 0 - C X 100%
= 100 - C

where, P = corrected mortality

O = observed mortality

C = 'controlled mortality'

3.7 DATA ANALYSIS

Data involving counts were transformed using square root (Y = Vx) while those 

involving percentages were transformed using arcsine Y = Sin'̂ (Vx/lOO) 

transformation before the data was analyzed using ANOVA (Udo, 2000). The 

transformation was to avoid the effect of zero counts and extreme values on the 

analysis. In all cases, mean separation was done using LSD.

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TABLE 3

TYPICAL ANALYSIS OF AGAR

Gel strength (Nika) 

Melting point

Setting point 

pH

Moisture 

Total ash 

Calcium 

Magnesium 

Sodium chloride

650-100g/m2 

88-95 °C 

32-35 °C.

7.0 7.4 

6 -  8 %

2 -  3 %

< 0.02 %

< 0.03 %

< 0.05 %

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PLATE 5 SITOPHILUS ZEAMAIS REARED ON MAIZE

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PLATE 6 CALLOSOBRUCHUS MACULA TUS REARED ON COWPEA

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POWDERED Z. XANTHOXYLOIDES STORED IN AIR TIGHT BOTTLES

PLATE 7

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CONTROLLED EXPERIMENTAL ROOM SHOWING JUTE BAGS 

CONTAINING GRAINS ARRANGED ON SHELVES.

PLATE 8

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ROTARY EVAPORATOR USED FOR EVAPORATING Z. XANTHOXYLOIDES

EXTRACTS.

PLATE 9

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AIR-TIGHT CONTAINERS USED IN PREPARING THE Z. 

XANTHOXYLOIDES TABLETS

PLATE 10

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Z. XANTHOXYLOIDES TABLETS REMOVED FROM THEIR CONTAINERS 

AND DISPLAYED ON A PLAIN SHEET

PLATE 11

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Z. XANTHOXYLOIDES TABLETS REMOVED FROM THEIR CONTAINERS 

AND DISPLAYED ON A PLAIN SHEET

PLATE 11

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ON-FARM STORAGE FACILITY (WOODEN CRIB) USED FOR STORING

GRAINS ON THE FARM.

PLATE 12

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CHAPTER 4

4.0 RESULTS

4.1 Yield of extracts

The percentage yield of methanol extracts from the various parts of Z  

xanthoxyloides is shown in Fig.1. The extracts were insoluble in acetone but 

soluble in water. The roots gave the highest yield of 31%. This was followed by 

the bark, which gave 24%, and then the leaves gave 19%. Estimation of the 

yield was done by first weighing the various parts of the plant from which the 

extracts were taken. It was then concentrated by evaporating to dryness and the 

concentrate weighed to determine the percentage of the product present.

4.2 Toxicity of various proportions of dry ground plant material

Comparing the control to the various proportions in Table 4, it can be observed 

that all the proportions showed various levels of bioactivity against S. zeamais 

and C. maculatus. There was a significant difference (P< 0.001) in mortality of 

both insects against the various treatments with the roots and bark causing 

above 70% mortality. Further tests conducted on the adult S. zeamais and C. 

maculatus using various proportions showed that 60% leaves and 40% bark, 

70% leaves and 30% bark, 60% leaves and 40% roots, and 70% leaves and 

30% roots induced 60% mortality after 1 week.

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4.3 Toxicity of various concentrations of the tablets

Table 5 shows the percentage mortalities of S. zeamais and C. maculatus in 

grains treated with different concentrations of Z  xanthoxyloides tablets. The 

various tablet concentrations showed some level of bioactivity against the two 

insect pests. Toxicity increased with increasing concentrations of the bark and 

root extracts. There was a significant difference (P< 0.001) in mortality of both 

insects against the various treatments with the 2.2 ml leaves and 1.8 ml roots,

2.4 ml leaves and 1.6 ml roots, 2.2 ml leaves and 1.8 ml bark and 2.4 ml leaves 

and 1.6 ml bark tablet concentrations being the most effective. The 2.2 ml leaves 

and 1.8 ml roots induced the highest mortality of nearly 50 percent and the 2.8 

ml leaves and 1.8 ml bark gave a mortality of almost 10 percent.

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FIG.

firesh
leaves

fresh roots 
31%

1 PERCENTAGE YIELD OF EXTRACTS OF DIFFERENT PARTS OF 
THE Z. XANTHOXYLOIDES

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PRELIMINARY INVESTIGATION OF THE MOST TOXIC

TABLE 4

DU ST PROPORTION OF Z. XANTHOXYLOIDES.

M O R T A L IT Y  ON THE SEVENTH DAY OF APPLICATION OF Z.
XANTHOXYLOIDES POWDER

LABORATORY RESULTS
Mean percentage mortality ± S.E

Treatment S. zeamais C. maculatus

60% L, 40% B 57.0 ± 3.4 78.0 ± 2.5
70% L, 30% B 51.0 ± 4.0 70.0 ± 2.2
80% L, 20% B 26.0 ± 1.9 56.0 ± 4.8
90% L, 10% B 21.0 ± 1.9 31.0 ± 1.9
60% L, 40% R 55.0 ± 3.5 67.0 ± 2.0
70% L, 30% R 69.0 ± 4.3 66.0 ± 4.3
80% L, 20% R 18.0 ± 1.2 32.0 ± 2.5
90% L, 10% R 11.0 ± 1.9 20.0 ± 3.5
100% L 10.0 ± 2.7 20.0 ± 1.6
100% B 70.0 ± 1.6 71.0 ± 2.9
100% R 72.0± 2.5 70.0 ± 1.6
Control 2.00 ± 1.2 2.0 ± 1.2
LSD (P< 0.001) 7.72 8.00

Treatment

FIELD RESULTS
Mean percentage mortality (± S.E'i
S, zeamais C. maculatus

60% L, 40% B 63.0 ± 2.0 67.0 ± 3.0
70% L, 30% B 56.0 ± 3.3 65.0 ± 3.5
60% L, 40% R 65.0 ± 3.2 68.0 ± 2.5
70% L, 30% R 58.0 ±4.1 65.0 ± 3.7
Control 2.0 ± 1.2 2.0 ± 1.2
LSD (P < 0.01) 8.13 8.65

Mean of five replicates of 20 insects.

60%L, 40%B= concentration of 60 percent leaves and 40 percent bark, 
70%L, 30%R= concentration of 70 percent leaves and 30 percent root, 
100% B -  concentration of 100 percent bark.

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TABLE 5

PRELIMINARY INVESTIGATION OF THE MOST TOXIC
Z. XANTHOXYLOIDES TABLET.

M O R T A L IT Y  ON THE SEVENTH DAY OF APPLICATION OF Z.
XANTHOXYLOIDES TABLET

LABORATORY RESULTS
Mean percentage mortality ± S.E

Treatment______________S. zeamais______________ C. maculatus

2.2 ml L, 1.8 ml R 37.60 ± 2.80 47.20 ± 1.90
2.4 ml L, 1.6 ml R 30.20 ± 3.00 41.80 ± 4.30
2.6 ml L, 1.4 ml R 17.80 ± 1.70 35.00 ± 3.60
2.8 ml L, 1.2 ml R 10.80 ± 1.60 12.80 ± 1.10
2.2 ml L, 1.8 ml B 39.60 ± 2.90 44.80 ±3.50
2.4 ml L, 1.6 ml B 34.40 ± 3.80 40.20 ± 3.00
2.6 ml L, 1.4 ml B 13.40 ± 2.00 20.20 ± 2.00
2.8 ml L, 1.2 ml B 9.60 ± 1.00 15.60 ± 1.80
Control 0.20± 0.20 0.40 ± 0.40
LSD (P < 0.001) 6.79 8.38

Mean of five replicates of 20 insects.

2.2 ml L. 1.8 ml R= tablet concentration of 2.2 ml leaves and 1.8 ml root
extracts,

2.8 ml L, 1.2 ml B= tablet concentration of 2.8 ml leaves and 1.2 ml bark
extracts,

2.4 ml L, 1.6 ml R= tablet concentration of 2.4 ml leaves and 1.6 ml root
extracts.

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4.4 Damage assessment of Z  xanthoxyloides du st.

Grains treated with dry ground material showed significant difference (P< 0.001) 

among the treatments in the reduction of the damage caused by S. zeamais and 

C. maculatus (Table 6). The control recorded a damage of over 12% during the 

trial period. Dry bark and roots provided almost complete protection to the grains 

against infestation by the two stored product pests by providing about 99% 

protection. Other tests conducted using 60% leaves and 40% bark, 70% leaves 

and 30% bark, 60% leaves and 40% roots, and 70% leaves and 30% roots 

provided about 96% protection to the grains in both the laboratory and on the 

field.

4.5 Damage assessment of Z  xanthoxyloides tablets .

The protective potential provided by the Z  xanthoxyloides tablets is shown in 

Table 7. There was a significant difference (P< 0.001) between the treatments in 

the reduction of the damage caused by the two stored product pests. The 2.2 mi 

leaves and 2.8 ml root tablets provided the highest protection of 96 percent and 

the 2.8 ml leaves and 1.2 ml bark provided the lowest protection of 91 percent. 

Percentage weight loss due to insect activities was used to determine the 

control.

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TABLE 6

Effect o f Zanthozylum xanthoxyloides on damage caused by S. zeamais
and  C.  macula tus

LABORATORY RESULTS
Mean percentage weight loss ± S.E 

T rea tm en t_____________S. zeamais__________ C. maculatus

60% L, 40% B 3.81 ± 0.50 3.85 ± 0.54
70% L, 30% B 4.70 ± 0.53 4.11 ± 0.42
60% L, 40% R 3.96 ± 0.42 3.75 ± 0.44
70% L, 30% R 4.29 ± 0.23 4.33 ± 024
100% L 8.12 ± 0.31 7.70 ± 0.33
100% B 0.98 ± 0.13 1.00 ± 0.13
100% R 1.05 ± 0.11 1.06 ± 0.34
Control 12.94 ± 0.24 12.63 ± 0.22
LSD (P< 0.01) 0.96 0.98

Treatment

FIELD RESULTS 
Mean percentage weight loss (± S.E')

S. zeamais C. maculatus

60% L, 40% B 4.29 ± 0.41 4.17 ± 0.23
70% L, 30% B 4.58 ± 0.14 4.42 ± 0.20
60% L, 40% R 4.31 ± 0.23 4.34 ± 0.22
70% L, 30% R 4.30 ± 0.24 4.50 ± 0.20
100% L 8.49 ± 0.21 8.24 ± 0.24

100% B 1.12 ± 0.13 1.06 ± 0.14
100% R 1.67 ± 0.10 1.32 ± 0.22
Control 13.65 ± 0.60 14.74 ± 0.73
LSD (P < 0.01) 0.87 0.89

Mean of four replicates of 20 insects.

60%L, 40%B= concentration of 60 percent leaves and 40 percent bark, 
70%L, 30%R- concentration of 70 percent leaves and 30 percent root, 
100%B = concentration of 100 percent bark.

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Table 7

Effect- o f Z. xanthoxyloides tablets on damage caused bv S. zeamais
and C, maculatus

Laboratory results 
Mean percentage weight loss (± S.E)

Treatment_______________ S. zeamais____________C. macuiatus

2.2 ml L, 1.8 ml R 4.83 ± 0.3 5.18 ± 0.3
2.4 ml L, 1.6 ml R 5.70 ± 0.2 5.73 ± 0.1
2.6 mi L, 1.4 ml R 7.08 ± 0.3 7.63 ± 0.3
2.8 ml L, 1.2 ml R 7.95 ± 0.3 8.20 ± 0.2
2.2 ml L, 1.8 ml B 5.35 ± 0.2 5.25 ± 0.3
2.4 ml L, 1.6 ml B 6.50 ± 0.4 6.35 ± 0.2
2.6 ml L, 1.4 ml B 8.03 ± 0.2 7.48 ± 0.3
2.8 ml L, 1.2 ml B 7.90 ± 0.4 8.05 ± 0.2
Control 12.68 ± 0.2 12.80 ± 0.2
LSD (P < 0.001) 0.81 0.69

Mean of five replicates of 20 insects.

2.2 ml L, 1.8 ml R= tablet concentration of 2.2 ml leaves and 1.8 ml root
extracts,

2.8 ml L, 1.2 ml B= tablet concentration of 2.8 ml leaves and 1.2 ml bark
extracts,

2.4 ml L, 1.6 ml R= tablet concentration of 2.4 mi leaves and 1.6 ml root
extracts.

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;.o Effect of Z . xanthoxyloides dust on eggs and immature stages

Grains treated with dry ground plant material significantly (P< 0.001) affected 

the eggs and the immature stages of both insects in the laboratory and on the 

field as summarized in (Tables 8a and 8b). Maize treated after 28 days of adult 

removal and cowpea treated after 20 days of adult removal, recorded the highest 

number of emergence than in treatments applied earlier than 28 days and 20 

days respectively.

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MEAN NUMBERS OF S. ZEAMAIS AND C  MACULATUS ADULTS THAT 
EMERGED FROM GRAINS TREATED WITH Z. XANTHOXYLOIDES DUST 
AFTER. DIFFERENT DAYS OF ADULT REMOVAL

TABLE 8 a

LABORATORY RESULTS

(DAYS'): 1 7 28
S. zeamais 
Control
60% L, 40% B 
70% L, 30% L 
60% L, 40% R 
70% L, 30% R 
100% L 
100% B 
100% R

1137.5 ± 108.7 
57.0 ± 8.7
63.7 ± 3.7 
46.5 ± 7.1
60.7 ± 11.1

148.5 ± 5.8
17.5 ± 1.7 
12.3 ± 1.3

1078.0 ± 67.6
63.7 ± 3.8 
74.2 ± 3.41
51.7 ± 9.8 
49.0 ± 10.1

147.8 ± 4.8 
8.5 ± 1.0 

14.5 ± 1.6

1505.2 ± 167.9 
118.2 ± 6.8
135.0 ± 3.5
126.0 ± 7.6
133.0 ± 9.3 
292.8 ± 16.3

64.7 ± 5.6 
48.5 ± 10.6

LSD (P< 0.01) 113.6 71.7 175.1

C. maculatus

(DAYS): 1 7 20

Control
60% L, 40% B 
70% L, 30% B 
60% L, 40% R 
70% L, 30% R 
100% L 
100% B 
100% R

1447.0 ± 134.1 
53.7 ± 6.8
53.2 ± 6.5
57.0 ± 8.1 
53.5 ± 4.1
132.0 ± 4.5
14.0 ± 1.9
14.3 ± 1.3

1112.0 ± 84.3
61.7 ± 5.6
49.7 ± 4.9 
39.0 ± 9.9
49.5 ± 5.5 

130.0 ± 6.8
12.3 ± 1.7
14.5 ± 2.3

1688.5 ± 31.9 
96.2 ± 2.5 

110.5 ± 13.8
99.7 ± 10.4 

126.0 ± 8.8 
234.3 ± 38.5
50.5 ± 4.1
43.7 ± 7.6

LSD (P< 0.01) 139.2 88.5 56.1

Mean of four replicates of 20 insects.

60%L, 40%B- concentration of 60 percent leaves and 40 percent bark,
70%L, 30%R= concentration of 70 percent leaves and 30 percent root,
100%B = concentration of 100 percent bark.

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MEAN NUMBERS OF S. ZEAMAIS AND C. MACULA TUS ADULTS THAT 
EMERGED FROM GRAINS TREATED WITH Z. XANTHOXYLOIDES DUST 
A FTER  DIFFERENT DAYS OF ADULT REMOVAL

TABLE 8 b

FIELD RESULTS

(DAYS): 1 7 28

S. zeamais
Control 1267.7 ± 112.3 1235 ± 113.1 1564.0 ± 45.1
60% L, 40% B 58.5 ± 7.8 62.0 ± 6.5 128.8 ± 8.9
70% L, 30% B 60.7 ± 5.3 57.7 ± 4.6 196.8 ± 39.1
60% L, 40% R 60.5 ± 7.4 47.5 ± 5.1 130.3 ± 6.1
70% L, 30% R 53.0 ± 8.9 53.7 ± 8.3 128.3 ± 9.2
100% L 139.3 ± 12.9 131.8 ± 14.1 323.3 ± 23.7
100% B 15.0 ± 1.3 10.5 ± 1.6 45.5 ± 2.9
100% R 13.5 ± 1.9 14.5 ± 2.9 55.0 ± 5.5
LSD (P< 0.01) 117.7 118.3 68.2

(DAYS): 1________________Z_________  20
C. maculatus
Control 1039.8 ± 77.6 1159.0 ± 75.3 1479.5 ± 215.5
60% L, 40% B 47.5 ± 6.1 50.5 ± 5.6 96.5 ± 7.2
70% L, 30% B 50.5 ± 5.9 45.5 ± 5.3 104.8 ± 9.5
60% L, 40% R 46.8 ± 6.4 50.3 ± 6.9 133.0 ±10.3
100% L 128.8 ± 5.0 133.0 ± 4.7 288.0 ± 22.0
100% B 17.5 ± 1.0 19.3 ± 0.85 64.3 ± 3.4
100% R_________ 15.3 ± 1.3____________18.3 ± 1.3_____ 53.8 ± 12.8
LSD (P < 0.01) 81.9 79.3 224.9

Mean of four replicates of 20 insects.

60%L, 40%B= concentration of 60 percent leaves and 40 percent bark, 
70%L, 30%R= concentration of 70 percent leaves and 30 percent root, 
100%B = concentration of 100 percent bark.

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4.7 Repl l ency bioassay of tablets

The various concentrations of the tablets showed various levels of repellence to 

both S. zeamais and C. maculatus (Table 9). S. zeamais was least repelled with 

the highest repellence of 32% in the 2.2ml leaves and 1.8ml roots tablet and the 

lowest repellence of 9% in the 2.8ml leaves and 1.2ml bark tablet. C. maculatus 

was repelled most. It recorded its highest repellence of 69% in the 2.2ml leaves 

and 1.8ml bark tablet and its lowest repellence of 19% in the 2.8ml leaves and 

1.2ml roots tablet.

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TABLE 9

Mean % repellency (pr) values for the tablets against S. zeam ais and
C.  maculatus in the choice test:

Mean % repellencv (PR)

TABLET CONCENTRATION S. ZEAMAIS C. MACULATUS

2.2ml leaves and 1.8ml roots 32 ± 0.23 62. ± 0.31

2.4ml leaves and 1.6ml roots 30 ± 1.21 56 ± 1.06

2.6ml leaves and 1.4ml roots 30 ± 0.11 28 ± 0.92

2.8ml leaves and 1.2ml roots 16 ± 0.14 19 ± 1.04

2.2m! leaves and 1.8ml bark 23 ± 1.15 69 ± 0.05

2.4ml leaves and 1.6ml bark 19 ± 0.01 57 ± 1.39

2.6ml leaves and 1.4ml bark 10 ± 0.62 50 ± 0.93

2.8ml leaves and 1.2ml bark 9 ± 1.80 44 ± 1.68

LSD (P< 0.05) 5.32 13.98

2.2 ml L, 1.8 ml R= tablet concentration of 2.2 ml leaves and 1.8 ml root
extracts,

2.8 ml L/ 1.2 ml B= tablet concentration of 2.8 ml leaves and 1.2 ml bark
extracts,

2.4 ml L, 1.6 rnl R- tablet concentration of 2.4 ml leaves and 1.6 ml root
extracts.

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4.8 PERSISTENCY TESTS OF Z. XANTHOXYLOIDES DUST

Ground Z  xanthoxyloides powder was able to protect the grains for two 

months. From Tables 10a and 10b, the 100% leaves treatments provided the 

lowest protection to both the maize and cowpea in both the laboratory and 

on the field while the greatest protection was provided by the 100% roots 

treatments in the first and the second months. During the third month, the 

number of insects found alive in all the treatments was almost the same as 

the control at P<0.001.

4.9 PERSISTENCY TESTS OF Z  XANTHOXYLOIDESTABLETS

All the Z  xanthoxyloides tablets were toxic and repellent to both S. zeamais 

and C. maculatus during first week of application irrespective of the dosage. 

The effectiveness of the tablets was significantly (P< 0.001) reduced to 

approximately zero during the second and third week of application 

irrespecctive of the dosage. From Table 11, there was no significant mortality 

in the insect pests after the second and third week as compared to the 

control.

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TABLE 10 a

 PERSISTENCY TEST OF Z . XANTHOXYLOIDES DUST

NUMBER OF ADULTS FOUND ALIVE AFTER EACH MONTH 

LABORATUORY RESULTS

FIRST MONTH SECOND MONTH THIRD MONTH
S. zeamais 
Control
60% L, 40% B 
70% L, 30% B 
60% L, 40% R 
70% L, 30% R 
100% L 
100% B 
100% R

86.80 ±3.10 
4.40 ± 1.20
4.60 ± 2.10
6.60 ± 1.90 
6.00 ± 1.50

10.80 ± 0.9
1.80 ± 0.7 
1.20 ± 0.6

76.80 ± 6.70
9.80 ± 0.90
9.20 ± 1.10 

10.00 ± 0.70
8.00 ± 1.30

11.80 ± 1.40
5.80 ± 1.10
5.20 ± 0.90

86.21 ± 3.10 
68.2 0± 3.30 
68.40 ± 4.10 
69.60± 4.60 
61.20± 4.30 
81.60 ± 5.20 
69.80± 5.70 
68.00± 4.60

LSD (P< 0,01) 4.87 7.38 12.74

NOAM MUMEAN NUMBER OF ADULTS FOUND ALIVE AFTER EACH MONTH

LABORATORY RESULTS

FIRST MONTH SECOND MONTH THIRD MONTH
C. maculatus 
Control
60% L, 40% B 
70% L, 30% B 
60% L, 40% R 
70% L, 30% R 
100% L 
100% B 
100% R

80.80± 3.70 
2.20 ± 1.10
2.00 ± 0.70
1.00 ± 0.80 
1.60 ± 0.50 
9.40± 1.20 
0.80 ± 0.60 
1.40 ± 0.70

81.20± 5.90
7.40 ± 1.10 
9.00 ± 0.80
7.40 ± 1.10 
8.60 ± 1.20

15.00 ± 1.00 
9.60± 1.00 
9.20± 1.20

82.80 ± 3.80 
61.60± 4.30 
63.00 ± 4.70 
61.60± 6.30 
60.40± 5.20
78.80 ± 3.90 
50.40± 4.90 
44.80± 3.80

LSD (P< 0.01) 4.39 6.65 13.53

60%l, 40%B= concentration of 60 percent leaves and 40 percent bark, 
70%L, 30%R= concentration of 70 percent leaves and 30 percent root, 
100% B = concentration of 100 percent bark.

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TABLE 10 b 

FIELD RESULTS

MEAN NUMBER OF ADULTS FOUND ALIVE AFTER EACH MONTH

FIRST MONTH SECOND MONTH THIRD MOP
S. zeamais 
Control 83.40 ±4.30

oXTCOr\ 6.90 87.40± 3.30
60% L, 40% B 1.80 ± 0.70 9.00 ± 0.70 G\ OO O O hb 8.10
70% L, 30% B 2.00 ± 1 .0 0 8.20± 1.50 75.60 ± 3.70
60% L, 40% R 5.20± 1.70 8.40± 0.90 69.00± 6.10
70% L, 30% R 6.40 ± 1.60 C

O o o H- 0.80 69.40± 5.00
100% L 9.80 ± 1.10 14.00± 0.70 78.40± 6.50
100% B 2.20 ± 0.90 9.20 ± 1.20 60.60± 5.10
100% R 1.40 ± 0.70 00 o o H- 1.10 87.40± 8.70
LSD (P< 0.01) 5.35 7.59 17.54

FIELD RESULTS

MEAN NUMBER OF ADULTS FOUND ALIVE AFTER EACH MONTH

FIRST MONTH SECOND MONTH THIRD MONTH
C . maculatus

Control 80.20± 4.70 83.60± 6.50 82.80± 3.30
60% L, 40% B 2.20 ± 0.90 8.60 ± 1.40 61.60± 7.80
70% L, 30% B 2.00 ± 0.70 9.60± 1.60 63.00 ± 5.10
60% L, 40% R 1.00± 0.50  9.00± 1.40 61.60± 5.60
70% L, 30% R 2.40 ± 0.50 9.80 ± 1.40 60.40± 6.40
100% L 9.40± 1.60 14.00± 0.70 78.80± 4.50
100% B 2.20 ± 0.60 11.40 ± 1.30 50.40± 7.60
100% R__________ 2.00 ± 0.70_________7.80± 0.70_______44.80± 3.50
LSD (p< 0.01) 5.35 7.47 13.53

60%L, 40%B= concentration of 60 percent leaves and 40 percent bark,
70%L, 30%R= concentration of 70 percent leaves and 30 percent root,
100%B = concentration of 100 percent bark.

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Table 11
PERSISTENCY OF Z. XANTHOXYLOIDES TABLETS

Laboratory results 
MEAN NUMBER OF ADULTS FOUND ALIVE AFTER EACH WEEK

S. zeamais
Treatment First week Second week Third week

2.2 ml L, 1 8 ml R 9.00 ± 1.50 19.67 ± 0.30 20.00 ± 0.00
2.4 ml L, 1 6 ml R 10.33 ± 1.20 20.00 ± 0.00 20.00 ± 0.00
2.6 ml L 14 ml R 12.33 ± 0.30 20.00 ± 0.00 19.67 ± 0.30
2.8 ml L, 1 2 ml R 13.67 ± 0.90 20.00 ± 0.00 20.00 ± 0.00
2.2 ml L, 18 ml B 7.33 ± 0.90 20.00 ± 0.00 20.00 ± 0.00
2.4 ml L, 16 ml B 8.67 ± 1.20 19.67 ± 0.30 20.00 ± 0.00
2.6 ml L, 14 ml B 13.00 ± 0.60 20.00 ± 0.00 20.00 ± 0.00
2.8 ml L, 12 ml B 17.00 ± 0.60 19.67 ± 0.30 20.00 ± 0.00
Control 20.00 ± 0.00 20.00 ± 0.00 19.33 ± 0.70
LSD (P < 0.001) 2.72 0.57 0.74

C. maculatus

MEAN NUMBER OF ADULTS FOUND ALIVE AFTER EACH WEEK

Treatment First week Second week Third week

2.2 ml L, 1.8 ml R 7.00 ± 0.60 20;00 ± 0.00 20.00 ± 0.00
2.4 ml L, 1.6 ml R 8.67 ± 1.80 20.00 ± 0.00 20.00 ± 0.00
2.6 ml L ,,1.4 ml R 11.00 ± 1.50 19.67 ± 0.30 20.00 ± 0.00
2.8 ml L, 1.2 ml R 16.33 ± 1.50 20.00 ± 0.00 20.00 ± 0.00
2.2 ml L, 1.8 ml B 7.33 ± 1.30 20.00 ± 0.00 20.00 ± 0.00
2.4 ml L, 1.6 ml B 8.33 ± 1.50 20.00 ± 0.00 20.00 ± 0.00
2.6 ml L, 1.4 ml B 14.67 ± 1.80 20.00 ± 0.00 20.00 ± 0.00
2.8 ml L, 1.2 ml B 16.33 ± 1.50 20.00 ± 0.00 20.00 ± 0.00
Control 20.00 ± 0.00 19.67 ± 0.30 20.00 ± 0.00
LSD (P < 0.001) 4.08 0.47 0.00

Mean of five replicates of 20 insects.
2.2 ml L, 1.8 ml R= tablet concentration of 2.2 ml leaves and 1.8 ml root 

extracts,
2.8 ml L, 1.2 ml B= tablet concentration of 2.8 ml leaves and 1.2 ml bark 

extracts,
2.4 ml L, 1.6 ml R= tablet concentration of 2.4 ml leaves and 1.6 ml root 

extracts.

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CHAPTER 5

5.0 DISCUSSION

5.1 Toxicity of ground materials

The dry ground materials obtained from the leaves, bark and roots of Z. 

xanthoxyloides were toxic to S. zeamais and C. maculatus. According to Adesina 

(1986), the high toxicity of the dry root and bark may be attributed to the 

presence of secondary metabolites, which are highly pungent. The toxicity of the 

secondary metabolites was evident in the various proportions prepared since the 

effective ones were the 60% leaves and 40% roots; 70% and 30% roots; 60% 

leaves and 40% bark and 70% leaves and 30% bark (Table 4). Zanthoxylol 

(Elujoba and Nagels, 1985) has been identified as a phenolic compound known 

for insecticidal activities (Wongo, 1998). Phenols are generally known to be an 

important source of potent bactericides, herbicides, fungicides and insecticides 

for pest control (Obeng-Ofori et a l, 1997). According to Bekele (1994), some 

secondary plant metabolites may act as both insecticides and antifeedant. Thus, 

a combination of more leaves and less bark or roots of Z. xanthoxyloides can be 

used to achieve maximum control of insect pests without destroying the plant. 

This can therefore be used to reduce the overuse of harmful synthetic 

insecticides to control stored maize and cowpea.

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5.2 Antifeedant activity of Z. xanthoxyloides

From Table 5, it can be observed that dry, ground leaf; bark and root of Z. 

xanthoxyloides reduced the feeding activity and damage caused by S. zeamais 

and C. maculatus at 5% (wt/wt) concentration with the roots and bark giving 

nearly 100% protection of the grains. The 60% leaves and 40% roots, 70% 

leaves and 30% roots, 60% leaves and 40% bark, and 70% leaves and 30% 

bark significantly reduced insect damage and increased insect mortality and this 

suggests that the plant acted as an antifeedant (Nawrot et al, 1988; Bekele, 

1994; Niber, 1994). The lowest protection offered by the leaves suggests that 

probably that part of the plant has low presence of secondary plant metabolites. 

This shows that Z. xanthoxyloides can be an essential supplement for synthetic 

insecticides and poor resource farmers could use its powder in traditional post- 

harvest systems in Africa to protect grains.

5.3 Effect of Z. xanthoxyloides powder on eggs and immature stages

Z. xanthoxyloides powder greatly reduced the number of emergence in adults 

form within 7 days after oviposition. The high activity of the powder may be due 

to a phenolic constituent which has been reported to inhibit the development of 

C. maculatus (Wongo, 1998). The high number of adult emergence recorded in 

the treatment after 28 days of oviposition as in the case of S. zeamais and 20

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days of oviposition as in the case of C. maculatus suggest that the secondary 

metabolites may not have had an effect on the beetles because at that time, 

majority of the eggs would have developed into pupae. The probable reason is 

that the pupal cases of the beetles might have offered protection against the 

insecticidal action of the plant. The inhibition of development of the eggs and 

immature stages within the grain kernels increases the protection potential of the 

Z  xanthoxyloides against insect damage in storage and can also provide poor- 

resource farmers an idea as to which stage of infestation they can protect their 

grains against, using Z. xanthoxyloides, since the plant has only ovicidal and 

lavicidal action.

5.4 Persistency of Z. xanthoxyloides dust

From Tables 8a and 8b, the persistence of Z  xanthoxyloides dust was for two 

months. The loss of activity after the second month may be attributed to 

evaporation and degradation of the chemicals in the plant. The persistency could 

be enhanced by developing suitable formulations or combining with natural plant 

oils in simple mixtures (Obeng-Ofori et al., 1997). In traditional post-harvest 

systems in Africa however, powdered dust formulations from Z  xanthoxyloides 

may be economical since the farmers themselves can produce it locally. Thus, Z  

xanthoxyloides could be used to reduce food insecurity caused by insects in 

grains on the African continent.

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5.5 Toxicity of Z. xanthoxyloides tablets

The Z. xanthoxyloides tablets showed various levels of toxicity to S. zeamais and

C. maculatus. The 2.2 ml leaves and 2.8 ml roots tablets induced the highest 

mortality of 47 percent in the C. maculatus and the 2.2 ml leaves and 2.8 ml 

bark tablets induced the highest mortality of 40 percent in the S. zeamais. These 

levels are low compared to the percentage mortalities obtained by the dust. The 

low levels of toxicity could be attributed to loss of some toxic volatile 

constituents through volatilization and during hardening of the tablets (Bekele, 

1994) and extraction (Obeng-Ofori, 1997). According to Udo (2000), the reduced 

susceptibility of the S. zeamais to the toxic effect of the tablets may depend on 

the size of the insect, adaptive physiology and mode of action of the active 

component of the fumigant. The reduced susceptibility of the insects to the toxic 

effects of the tablets may be attributed to the fact that response of insects to 

toxic effects of plant metabolites depends on their sex, size, age and 

physiological status (Busvine, 1971). As observed in the dust, beetles killed in 

treated grains had their metathoracic wings unfolded and stretched outside the 

elytra. This, according to Obeng-Ofori et al (1997), probably suggests that, 

toxicity was not due to only ingestion of treated grains but also due to inhalation 

of toxicants. Ryan and Byrne (1988) attributed the toxicity of several terpenoids, 

representing a wide range of functional groups including Zanthoxylol, Atarine, 

Gamma-fagaronine and Pseudo-fagarol to their reversible competitive inhibition

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of x.-tyl cholinesterase by apparently occupying the hydrophobic site of the

enzyme's active centre.

5.6  e f fect of Z. xanthoxyloides tablets on feeding activity of S.

zeamais and C. maculatus.

The Z. xanthoxyloides tablets provided different levels of activity in protecting 

the grains against insect attack. The 2.2 ml leaves and 2.8 ml root tablets 

provided the highest protection of 96 percent for the maize and the 2.8 ml leaves 

and 1.2 ml bark provided the lowest protection of 91 percent for the cowpea. 

The protection of the grains coupled with the mortalities observed suggests the 

antifeedant properties in the plant (Udo, 2000). The low protection observed in 

the tablets as compared to the dust could be attributed to the loss of toxic 

volatile secondary constituents during drying and extraction process of the 

tablets (Bekele, 1994). Though the dust offered a much higher protection than 

the tablets, it may not be much preferred by consumers since it leads to 

qualitative losses. Thus, the toxicity of the tablets could further be improved for 

protection against post- harvest damage caused by insects. According to Casida

(1990), the bioactivity of the different parts of the plant against stored product 

insects may depend on several factors, including chemical composition, species 

susceptibility and variation in insect behaviour.

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5.7 Repellency of the Z  xanthoxyloides tablets

The various tablets were repellent to both S. zeamais and C. maculatus. S. 

zeamais adults were least repelled as compared to C. maculatus. The difference 

in r e p e llence may be attributed to the fact that the immature stages of the S. 

zeamais Is always found within the grains whiles both the immature and mature 

stages cf C. maculatus is always confined to the surface of the grains. The 

repellent effect of the tablet may be attributed to the presence of secondary 

metabolites in Z  xanthoxyloides. According to Bekele (1994), secondary plant 

metabolites have been shown to have both attractive and repellent properties. 

This repellent action coupled with its inhibition of development of eggs and 

immature stages within the grains and progeny emergence increases the 

protectant potential of the plant against insect damage in storage. However, a 

detailed investigation of the individual constituent of the plant would shed m o re  

light on the protection potential of the plant. 5- /

5.8 Persistency of Z. xanthoxyloides tablets "

Effect from Z  xanthoxyloides tablets was persistent for only one week. The 

highly significant loss of activity after the first week (as explained earlier for the 

dust) may be attributed to rapid evaporation and degradation of the chemical 

constituents in the tablets. This may be related to the physico-chemical 

behaviour of the compounds to the grains. Most unprocessed foodstuffs, such as

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maize and cowpea, lack polar surfaces to which treated chemical may be bound 

to reduce its volatilization (Weaver et al, 1994).

Botanicals, represent an important potential for Integrated Pest Management 

Strategies in developing countries because they have a broad spectrum action, 

based on local materials and potentially less expensive to the traditional farmer 

(Obeng-Ofori e t al., 1997). A lot of these botanicals are safe to the environment 

and man, mammals and beneficial arthropods (Talukder and Howse, 1994).

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CHAPTER 6 

CONCLUSION AND RECOMMENDATIONS

The results obtained from this study have shown that Z  xanthoxyloides has 

insecticidal, antifeedant, ovicidal, lavicidal and repellent properties against some 

stored product beetle pests. The study has also shown that the dust formulation 

is more effective as a toxicant, grain protectant and highly persistent than the 

tablet formulation (fumigation). Candlewood was also found to be effective in the 

field. The most effective proportions of the dust were 60% leaves and 40% 

roots, 70% leaves and 30% roots, 60% leaves and 40% bark and 70% leaves 

and 30% bark. Whilst the effective tablet concentrations were 2.2 ml leaves and

1.8 ml roots, 2.4 ml leaves and 1.6 ml roots, 2.2 ml leaves and 1.8 ml bark and 

2.4 ml leaves and 1.6 ml bark.

It is recommended that, an extensive study be made to improve the efficacy of 

the tablets since grains treated with tablets do not lead to qualitative losses as 

compared to those treated with the dust. An extensive work should also be made 

on the biological active compounds in Z  xanthoxyloides for the control of not 

only stored product pests but also other household pests. Furthermore, 

secondary plant metabolites do not always have the same concentration 

throughout the year. Research should therefore be conducted at different 

seasons of the year to determine the peak period of activity of the secondary 

metabolites.

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Further work should focus on the precise mode of action of the active 

components, its penetration into the insect cuticle and grain as well as the 

metabolic targets in the insect body.

It is also recommended that since the LD50 of various proportions of extracts and 

dust mixed together cannot be determined, the LT50of the effective proportions 

should be determined in order to get the minimum amount of the biopesticide 

that can achieve maximum control.

In order to incorporate the use of the plant products into Integrated Pest 

Management Strategies, the residue levels on crops, its effect on beneficial 

arthropods as well as its toxicological effect on mammals fed on treated grains 

need to be investigated.

Finally, local initiatives aimed at preparation of this traditional botanical 

insecticide that is cheap, readily available, effective, less toxic to mammals and 

environmental friendly at the farm level, should be promoted for resource-poor 

farmers who have no access to commercial pesticides or cannot afford them.

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REFERENCES

Abbott's W.S., (1925). A method for computing the effectiveness of an 

insecticide. Journal o f Economic Entomology. 18,265-267.

Addae-Mensah, I., (1998). The uses of the neem Azadirachta indica A. Juss 

in Ghana and their relationships to the chemical constituents and 

biological activities. In: The potentials of the neem tree in Ghana. 

Proceedings of a seminar held in Dodowa, Ghana GTZ, Eschborn. 11-26.

Adesina, S. K., (1986). Further novel constituents of Zanthoxylum 

xanthoxyloides root and pericarp. Journal of natural products. 49(4), 715- 

716.

Alkofahi, A; Rupprecht,J.K; Anderson,J.E; McLaughlin,J.L; Mikolajczak, 

K.L. and Scott, B.A.(1989) Search for new pesticides from higher 

plants In: Insecticides of plant origin. ACS symposium series 387̂  

American Chemical Society. 25-43

Alzouma, 1.(1990). The Post-harvest situation on Sahel. In: Post Recolte en 

Afrique, Abijan (Cote d'Ivoire), 29th January l990. Proceedings-AUPELP- 

UREF, Paris (France). 9, 22-28.

Anon., (1958). Stored grain pests. USDA Farmers Bulletin 1260. 88pp.

Anonymous, A. (1972). Report on the Expect Panel on Integrated Pest 

Control. Dec.1972. F.A.O., Rome, Italy.

Anon., (1982). Plant protection legislation. FAO. Rome.165 pp

74

University of Ghana                              http://ugspace.ug.edu.gh



Anon., (1991). Recommendations on the symposium on resources for 

sustainable Agriculture: The use of neem and other plant materials for 

pest control and rural development. Neem Symposium. XVII Pacific 

Science Congress (Honolulu: East-West Center), pp. 1-11 

Appert, J. (1958). The storage of food grains and seeds. The Tropical 

Agriculturalist. McMillan, London. 146pp.

Ayertey J.N. (1979). The control of some pests of stored maize using methyl 

bromide or phosphine. Ghana Journal o f Agricultural Science. 12,113- 

124.

Ayertey J.N. (1982). Development of Sitotrogpa cerealella on whole, cracked 

or ground maize. Entomologia, Experimentalis et Applicata 31, 165-165 

Ayertey, J.N. (1986). The role of plant protect in grain storage. An invited 

paper at the symposium on "The role of plant protection in crop storage" 

-16th Annual Conference, Nigerian Society for Plant Protection, A.B.U 

Zaria, 16-20 March, 1986.

Bartali, E,H. (1990). The Post-harvest situation in North Africa. In: Post- 

R'Colte en Afrique, Abidjan (Cote d'Ivoire) 29th January 1990. Proceeding- 

AUPELF-UREF, Paris (France). 17-21.

Bekele, A.J (1984). Effect and use of some Ocimum plant species and their 

essential oils on some storage insect pests. Ph.D thesis, University of 

Nairobi. 200 pp.

75

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Bekele, AJ. Obeng-Ofori, D. and Hassanali, A. (1997). Evaluation of 

Ocimum kenyense (Ayobangira) as source of repellents, toxicants and 

protectants in storage against three major stored product insect pests. 

Journal o f Applied entomology. 121,163-173.

Booker, R.H (1967). Observation on three bruchids associated with cowpeas in 

Northern Nigeria. Journal o f Stored Products Research, 3 (1) 1-15.

Boxall, R.A. (1986). A critical review of the methodology for assessing farm- 

level grain losses after harvest. Tropical Development and Research 

Institute 191, 99-139.

Carson, R. (1962). Silent Spring. Boston: Houghton, Miffin.368 pp.

Casida, J. H. (1990). Pesticide mode of action: evidence for and implications of 

a finite numbe