DIVERSITY AND ABUNDANCE OF ARTHROPODS AND PREDATORS OF THE 

FALL ARMYWORM, SPODOPTERA FRUGIPERDA (J.E. SMITH) (LEPIDOPTERA: 

NOCTUIDAE) IN MAIZE AGROECOSYSTEMS AND THEIR POTENTIAL FOR 

BIOLOGICAL CONTROL 

 

 
BY 

ITOHAN IDEMUDIA 

ID. NO: 10802350 

 

A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL 

FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF DEGREE OF 

MASTER OF PHILOSOPHY (M.PHIL.) IN ENTOMOLOGY. 

 

 
AFRICAN REGIONAL POSTGRADUATE PROGRAMME IN INSECT SCIENCE 

(ARPPIS) 

UNIVERSITY OF GHANA, LEGON. 

 

 
DECEMBER 2021 

 

 
* JOINT INTERFACULTY INTERNATIONAL PROGRAMME FOR THE TRAINING 

OF ENTOMOLOGISTS IN WEST AFRICA. 

 

 
COLLABORATING DEPARTMENTS: 

ANIMAL BIOLOGY AND CONSERVATION SCIENCES 

(SCHOOL OF BIOLOGICAL SCIENCES) 

AND 

CROP SCIENCE 

(SCHOOL OF AGRICULTURE) 

COLLEGE OF BASIC AND APPLIED SCIENCES 

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DECLARATION 

 
I, ITOHAN IDEMUDIA, hereby declare that this thesis is the result of my original work personally 

undertaken by me for the award of Degree of Master of Philosophy in Entomology at the African 

Regional Postgraduate Programme in Insect Science (ARPPIS) in the University of Ghana and has 

not been presented elsewhere in part or whole for the award of a degree. All the references to other 

people’s work have been duly acknowledged. 

 

Signature………………………………..                 Date…………………………………….. 

ITOHAN IDEMUDIA 

 

 

 

Signature………………………………..                 Date…………………………………….. 

DR. KEN OKWAE FENING (PRINCIPAL SUPERVISOR 

 

 

 

 

 

Signature………………………………..                 Date…………………………………….. 

DR. DAVID WILSON (CO-SUPERVISOR) 

 
 

11-09-22

Sep 11, 2022

11-09-2022

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ABSTRACT 

 
The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) is native to the 

tropical and subtropical regions of the Americas. It is currently the most devastating invasive 

arthropod pest of maize in sub-Saharan Africa. Following the first report of S. frugiperda in Ghana 

in 2016, its control has been reliant on synthetic chemical insecticides. Due to reliance and overuse 

of these insecticides, the pest has evolved resistance and requires higher application frequencies 

for control. Furthermore, non-target/beneficial organisms are negatively impacted by insecticides. 

Therefore, this thesis sought to investigate the role of two different management options of S. 

frugiperda on the diversity and abundance of arthropod species, including predators as well as the 

infestation levels of S. frugiperda in maize agroecosystems at the Soil and Irrigation Research 

Centre (SIREC) of the University of Ghana, Kpong, located within the lower Volta basin of the 

Coastal Savannah agro-ecological zone of Ghana. The investigations were conducted in the major 

and minor maize cropping seasons. Also, evaluations of the predatory potential and functional 

response of the predator Rhynocoris bicolor (Fabricius) were made following the 

recommendations by the Centre of Agriculture and Bioscience International (CABI) and the Plant 

Protection and Regulatory Services Directorate (PPRSD) of the Ministry of Food and Agriculture 

(MoFA). The field experiment consisted of two different treatment plots: a biocontrol maize plot 

(BCM) where augmentative releases of the egg parasitoid, Telenomus remus (Nixon) were made 

and maize plot with farmer’s practice (MFP) in which the insecticide; Emamectin benzoate-based 

product, Ataka Super EC®: Emamectin benzoate 19.2 g/l was applied. A control maize plot without 

any treatment was included. The predatory potential of the predator R. bicolor was determined in 

laboratory assays at the PPRSD biocontrol laboratory in Pokuase, Accra. Results showed that both 

in the major and minor maize cropping seasons, significantly more arthropods, including predators 

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were recorded in the control plots than in the MFP plots. Further, the diversity of the arthropods 

including predators was significantly lower in the MFP plot than in the control and BCM plots, 

articulating that the insecticides used by maize growers in Ghana had adverse effects on the 

arthropod communities and reduce biocontrol services. Conversely, a total of seven predatory 

arthropods: Crematogaster striatula (Emery), Cosmolestes pictus (Klug), Haematochares 

obscuripennis (Stal), Hediocoris tibialis (Stal), Rhynocoris sp. Sphedanolestes picturellus 

(Schouteden), and Misumenops sp. were confirmed predators of S. frugiperda after laboratory 

tests. The laboratory assays on R. bicolor revealed that the predator exhibits a type II functional 

response, with S. frugiperda as prey. Hence, could be considered a potential biocontrol agent of S. 

frugiperda in Ghana. 

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DEDICATION 

 
This thesis is dedicated to my darling husband, Dr. Pascal Osabhahiemen Aigbedion-Atalor and 

my beloved son, Aaron Obosaebhihiaye Aigbedion-Atalor for their immense love and support. 

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ACKNOWLEDGEMENT 

 
Firstly, my greatest gratitude goes to the Almighty God for His abundant grace and strength on me 

all through the two (2) years of my study. 

 
 

Sincere thanks to the German Academic Exchange Service (DAAD) for awarding me the ARPPIS- 

DAAD scholarship to pursue this M.Phil. Programme at the University of Ghana. 

 
 

I wish to express my profound gratitude to my supervisors, Dr. Ken Okwae Fening, Dr. David 

Wilson and Dr. Lakpo Koku Agboyi for their immense commitment and contributions to this 

project. I am very thankful for the effective supervision, moral support, guidance and love they 

offered to me that made this work a reality. Further, I would like to reiterate my appreciation to 

my Principal supervisor, Dr. Ken Okwae Fening, for his magnanimity, benevolence, and 

understanding that I enjoyed throughout this study. 

 
 

I am sincerely thankful to the Coordinator of ARPPIS, Dr. Ken Okwae Fening and all the ARPPIS 

lecturers for the quality of the training provided to me. 

 
 

Special appreciation to the Centre of Agriculture and Bioscience International (CABI) through the 

Project Manager – Invasive Species Management West Africa, Dr. Lakpo Koku Agboyi, for 

funding the research work. 

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Appreciation is also extended to the staff of the University of Ghana Soil and Irrigation Research 

Centre (SIREC) and the Plant Protection and Regulatory Services Directorate (PPRSD) of the 

Ministry of Food and Agriculture (MoFA) for giving me space to carry out the research. 

 
 

Many thanks to Dr. Ali Maru of the University of Ghana Soil and Irrigation Research Centre 

(SIREC) for his guidance in the thesis write-up and training on Microsoft suites. 

 
 

I also appreciate the support given to me by my colleague, Babatounde Ferdinand Rodolphe 

Layode and other classmates of ARPPIS 2019. 

 
 

Finally, my sincere gratitude goes to my ever-loving husband, Dr. Pascal Osabhahiemen 

Aigbedion-Atalor for making out time despite his busy schedule to patiently guide, listen and 

correct my numerous mistakes. I am very thankful to my mother, siblings and in-laws for their 

constant prayers and words of encouragement. 

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TABLE OF CONTENTS 

DECLARATION ............................................................................................................................. i 

ABSTRACT .................................................................................................................................... ii 

DEDICATION ............................................................................................................................... iv 

ACKNOWLEDGEMENT ................................................................................................................ v 

TABLE OF CONTENTS .............................................................................................................. vii 

LIST OF FIGURES .......................................................................................................................... x 

LISTS OF TABLES ...................................................................................................................... xii 

LIST OF PLATES .........................................................................................................................xiv 

LIST OF ACRONYMS .................................................................................................................. xv 

CHAPTER ONE .............................................................................................................................. 1 

INTRODUCTION ............................................................................................................................ 1 

1.1 Background information ......................................................................................................... 1 

1.2 Justification ............................................................................................................................. 3 

1.3 Objective ................................................................................................................................. 5 

1.3.1 Main objective ................................................................................................................. 5 

1.3.2 Specific objectives ........................................................................................................... 5 

CHAPTER TWO.............................................................................................................................. 6 

LITERATURE REVIEW ................................................................................................................. 6 

2.1 Origin and distribution of Spodoptera frugiperda .................................................................. 6 

2.2 Taxonomic identity, description and biology of Spodoptera frugiperda ............................... 8 

2.2.1 Taxonomic identity .......................................................................................................... 8 

2.2.2 Description and biology ................................................................................................... 8 

2.2.2.1 Egg ............................................................................................................................ 9 

2.2.2.2 Larva ....................................................................................................................... 10 

2.2.2.3 Pupa ......................................................................................................................... 12 

2.2.2.4 Adult male ............................................................................................................... 13 

2.2.2.5 Adult female ............................................................................................................ 13 

2.3 Movement and dispersal ....................................................................................................... 14 

2.4 Host range of Spodoptera frugiperda ................................................................................... 15 

2.5 Damage and impacts of Spodoptera frugiperda ................................................................... 15 

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2.6 Management of Spodoptera frugiperda................................................................................ 18 

2.6.1 Cultural control .............................................................................................................. 18 

2.6.2 Chemical control ............................................................................................................ 19 

2.6.3 Botanicals ....................................................................................................................... 20 

2.6.4 Push-pull technology (PPT) ........................................................................................... 21 

2.6.5 Host plant resistance ...................................................................................................... 22 

2.6.6 Pheromonal control ........................................................................................................ 23 

2.6.7 Biological control ........................................................................................................... 23 

2.6.7.1 Biopesticides ........................................................................................................... 23 

2.6.7.2 Parasitoids ............................................................................................................... 24 

2.6.7.2 Predators .................................................................................................................. 26 

2.6.8 Integrated management of Spodoptera frugiperda ........................................................ 28 

CHAPTER THREE ........................................................................................................................ 29 

MATERIALS AND METHODS ................................................................................................... 29 

3.1 Field experimental site.......................................................................................................... 29 

3.2 Experimental design and treatments ..................................................................................... 30 

3.3 Land preparation and maize cultivation ............................................................................... 32 

3.4 Weed management ............................................................................................................... 32 

3.5 Fertilizer application ............................................................................................................. 33 

3.6 Insecticide application .......................................................................................................... 33 

3.7 Data collection ...................................................................................................................... 33 

3.7.1 Field sampling and data collection ................................................................................. 33 

3.7.1.1 Sampling for general arthropods ............................................................................. 34 

3.7.1.2 Sampling for arthropod predators ............................................................................ 35 

3.7.1.3 Assessing infestation levels of Spodoptera frugiperda ........................................... 36 

3.7.1.4 Meteorological data ................................................................................................. 37 

3.7.2 Arthropod identification and laboratory assays ............................................................. 37 

3.7.2.1 Identification ........................................................................................................... 37 

3.7.2.2 Potential of the predator, Rhynocoris bicolor as a biological control agent of 

Spodoptera frugiperda ........................................................................................................ 38 

3.8 Statistical analysis ................................................................................................................. 43 

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3.8.1 Relative abundance and diversity ................................................................................. 43 

3.8.2 Infestation level of Spodoptera frugiperda ................................................................... 43 

3.8.3 Predation rate and functional response of Rhynocoris bicolor ...................................... 44 

CHAPTER FOUR ......................................................................................................................... 47 

RESULTS ..................................................................................................................................... 47 

4.1 Diversity and abundance of general arthropod communities associated with maize 

agroecosystems .......................................................................................................................... 47 

4.1.1 Major maize cropping season ........................................................................................ 47 

4.1.2 Minor maize cropping season ....................................................................................... 55 

4.1.3 Diversity indices ........................................................................................................... 63 

4.2 Diversity and abundance of predators and Spodoptera frugiperda infestation levels ......... 63 

4.2.1 Abundance of predators ................................................................................................ 63 

4.2.2 Diversity indices ........................................................................................................... 69 

4.2.3 Spodoptera frugiperda infestation levels ...................................................................... 69 

4.2.3.1 Influence of Climate on Spodoptera frugiperda infestation levels ........................ 72 

4.3 Potential of the predator, Rhynocoris bicolor as a biological control agent of Spodoptera 

frugiperda .................................................................................................................................. 73 

4.3.1 Predation rate ................................................................................................................ 73 

4.3.2 Functional response of Rhynocoris bicolor .................................................................. 76 

CHAPTER FIVE ........................................................................................................................... 83 

DISCUSSION ............................................................................................................................... 83 

5.1 Diversity and abundance of general arthropod communities associated with maize 

agroecosystems .......................................................................................................................... 83 

5.2 Diversity and abundance of predators and Spodoptera frugiperda infestation levels ......... 85 

5.3 Predation rate and functional response of Rhynocoris bicolor, a potential biological control 

agent of Spodoptera frugiperda ................................................................................................. 87 

CHAPTER SIX ............................................................................................................................. 90 

CONCLUSION AND RECOMMENDATIONS .......................................................................... 90 

6.1 Conclusion ........................................................................................................................... 90 

6.2 Recommendations ................................................................................................................ 91 

REFERENCES .............................................................................................................................. 92 

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LIST OF FIGURES 

 
Figure 2.1: Global occurrence and distribution of Spodoptera frugiperda .................................... 6 

Figure 2.2: Occurrence and distribution of Spodoptera frugiperda in Ghana ............................... 7 

Figure 2.3: Life cycle of Spodoptera frugiperda ........................................................................... 9 

Figure 2.4: Eggs of Spodoptera frugiperda ................................................................................. 10 

Figure 2.5: Neonate and the six instar larvae stages of Spodoptera frugiperda. .......................... 11 

Figure 2.6: Pupa of Spodoptera frugiperda ................................................................................. 13 

Figure 2.7: Adult female and male Spodoptera frugiperda ......................................................... 14 

Figure 3.1: Map of Ghana showing the study site: Soil and Irrigation Research Centre (SIREC) 

of the University of Ghana in Kpong where the field research component of this thesis was 

undertaken from May to November 2020. .................................................................................... 30 

Figure 3.2: Schematic design showing the sampling points and the number of sampled maize 

plants in the stratified sampling (i.e., the ‘X pattern’) method. MPs = Maize plants. .................. 35 

Figure 4.1: Weekly abundance (mean ±SE) of predators in the treatments (BCM and MFP) and 

control plots in the (a) major maize cropping season, and (b) minor maize cropping season.   68 

Figure 4.2: Weekly infestation level of Spodoptera frugiperda in the treatment (BCM and MFP) 

and control plots. (a) = larvae counts in the major maize cropping season, (b) egg mass counts in 

the major maize cropping season, (c) larvae counts in the minor maize cropping season, and (d) 

egg mass counts in the minor maize cropping season. .................................................................. 70 

Figure 4.3: Spodoptera frugiperda infestation (Egg batch and larvae density) in the two different 

treatments and control plots in the (a) major maize cropping season and (b) minor maize cropping 

season. Error bars with lowercase letters compared variations in egg batches, while uppercase 

letters compared variations in larvae densities. Different letters in each instance (i.e. lowercase and 

uppercase) indicate significantly different following a Kruskal-Wallis (P < 0.05) and Dunn’s 

multiple comparison tests. Note: Each egg batch indicate a count > 50 eggs/batch. .................... 71 

Figure 4.4: Climate parameters (temperature and rainfall) occurring in the major (May -August) 

and minor (August - November) cropping seasons. ...................................................................... 73 

Figure 4.5: Type II functional response curves fitted by Rogers decreasing prey function random 

predator equation Rhynocoris bicolor nymphs (a) I, (b) II, (c) III, (d) IV, and (e) V, preying on 

newly-emerged (< 1 day old) Spodoptera frugiperda larvae in a 6-hour period. ......................... 79 

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Figure 4.6: Type II functional response curves fitted by Rogers decreasing prey function random 

predator equation Rhynocoris bicolor nymphs (a) I, (b) II, (c) III, (d) IV, and (e) V, preying on 2- 

day old Spodoptera frugiperda larvae in a 6-hour period. ............................................................. 80 

Figure 4.7: Type II functional response curves fitted by Rogers decreasing prey function random 

predator equation for Rhynocoris bicolor males preying on (a) newly-emerged, (b) 2-day old, (c) 

6-day old Spodoptera frugiperda larvae and females preying on (d) newly-emerged, (e) 2-day old, 

and (f) 6-day old S. frugiperda larvae in a 6-hour period. .............................................................. 81 

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LISTS OF TABLES 

 
Table 2.1: Yield losses in maize caused by Spodoptera frugiperda in some African countries, 

including Ghana ............................................................................................................................ 17 

Table 3.1: List of the experimental plots and their GPS coordinate in the experimental field site in 

SIREC ........................................................................................................................................... 31 

Table 4.1: Order, family, and species diversity of arthropod communities in maize plots with 

farmers’ practice (MFP) in the major maize cropping season and parameters of Shannon index 

diversity calculation ...................................................................................................................... 48 

Table 4.2: Order, family, and diversity of arthropod communities in the control plots (i.e. without 

any applied treatment) in the major maize cropping season and parameters of Shannon index 

diversity calculation ...................................................................................................................... 51 

Table 4.3: Order, family, and species diversity of arthropod communities in maize plots with 

farmers’ practice (MFP) in the minor maize cropping season and parameters of Shannon index 

diversity calculation ...................................................................................................................... 56 

Table 4.4: Order, family, and diversity of arthropod communities in the control plots (i.e. without 

any applied treatment) in the minor maize cropping season and parameters of Shannon index 

diversity calculation ...................................................................................................................... 59 

Table 4.5 Diversity indices of arthropod species in the treatment (MFP) and control plots in the 

major and minor maize cropping seasons ..................................................................................... 63 

Table 4.6: Predators occurring in the treatment (BCM and MFP) and control plots in the major 

and minor maize cropping season ................................................................................................. 64 

Table 4.7: Predators attacking Spodoptera frugiperda in the laboratory. Unfortunately, colonies 

of the predators were unsuccessfully reared for further testing and assessments. ......................... 67 

Table 4.8: Diversity indices of predators in the treatments (BCM and MFP) and control plots in 

the major and minor maize cropping seasons ............................................................................... 69 

Table 4.9: Spodoptera frugiperda egg batches and larvae infestation levels (pooled from the BCM, 

MFP, and control plots) recorded in the major and minor maize cropping season ....................... 72 

Table 4.10: Mean number (± SE) of prey (S. frugiperda larvae), at different prey densities, 

consumed by the five nymph stages and adults (female and male) of Rhynocoris bicolor. n: number 

of replicates. .................................................................................................................................. 75 

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Table 4.11: Logistic regression analysis of the proportion of host age of Spodoptera frugiperda 

predated by all life-stages of Rhynocoris bicolor in the R environment for statistical computing 

(version 4.00) ................................................................................................................................. 77 

Table 4.12: Functional response estimates of a = attack rate and Th = handling time during the 

considered time interval (6 hours) of the five nymphs and adults of Rhynocoris bicolor, and the 

95% CI = confidence interval ......................................................................................................... 82 

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LIST OF PLATES 

 
Plate 2.1: Spodoptera frugiperda feeding damage on maize (A) leaves, (B) whorl, and (C) cob. 

....................................................................................................................................................... 16 

Plate 3.1: Experimental field with (a) affixed sticky traps in the field, (b) trap positions in the field, 

and (c) trap catches. ....................................................................................................................... 34 

Plate 3.2: Visual examination of maize plants in the sampling area (“X” pattern) for predators of 

the S. frugiperda ............................................................................................................................ 36 

Plate 3.3: Laboratory set-up for rearing Spodoptera frugiperda .................................................. 39 

Plate 3.4: Life stages of Rhynocoris bicolor (a) male and female R. bicolor in the rearing arena, 

(b) newly hatched eggs of the female R. bicolor, (c) 1st Nymphal stage of R. bicolor, (d) 2nd 

Nymphal stage of R. bicolor, (e) 3rd Nymphal stage of R.bicolor, (f) 4th Nymphal stage of R. 

bicolor, (g) 5th Nymphal stage of R. bicolor, (h) dorsal view of male (i) ventral view of male, (j) 

dorsal view of female, (k) ventral view of female attached with a newly killed S. frugiperda larva. 

....................................................................................................................................................... 40 

Plate 3.5: Experimental design and replicates used in assessing the functional response of R. 

bicolor with S. frugiperda as prey in a six-hour assay .................................................................. 42 

Plate 4.1: Some predators attacking Spodoptera frugiperda in the laboratory. These predators were 

collected from the treatments (BCM and MFP) and control plots. ............................................... 67 

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LIST OF ACRONYMS 

 
ALP - Alkaline phosphatase 

ARPPIS - African Regional Postgraduate Programme in Insect Science 

BCM - Biocontrol maize plot 

BNARI - Biotechnology and Nuclear Agriculture Research Institute 

CABI - Centre of Agriculture and Bioscience International 

CIs - Confidence intervals 

CRD - Completely randomized design 

DAAD - German Academic Exchange Service 

EPPO - European Public Prosecutor's Office 

FAO - Food and Agriculture Organization 

FAOSTAT - Food and Agriculture Organization Corporate Statistical Database 

GAEC - Ghana Atomic Energy Commission (GAEC) 

IFPRI - International Food Policy Research Institute 

IITA - International Institute of Tropical Agriculture 

IPM - Integrated pest management 

M.PHIL.-Master of Philosophy 

MFP - Maize plot with farmer’s practice 

MoFA - Ministry of Food and Agriculture 

MPs - Maize plants 

Mt/ha - Metric tons per hectare 

PPRSD - Plant Protection and Regulatory Services Directorate 

PPT - Push-pull technology 

SIREC - Soil and Irrigation Research Centre 

SSA - sub-Saharan Africa 

UF/IFAS - University of Florida's Institute of Food and Agricultural Sciences 

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CHAPTER ONE 

 

INTRODUCTION 
 

1.1 Background information 

 

Maize (Zea mays L.), also referred to as corn, is a cereal crop belonging to the grass family 

Poaceae, originating from the Western hemisphere (Fast and Caldwell 2000). It is ranked third, 

after rice and wheat, as the world's most cultivated cereal crop, and it is grown on approximately 

197 million hectares in more than 125 developing countries (FAOSTAT, 2021). Maize is a 

fundamental driver of food security and sustainable livelihood in developing countries (De 

Groote et al., 2013). The demand for maize has been projected to double in the developing world 

by 2050 (Rosegrant et al., 2009). Maize accounts for approximately 30% of the daily food caloric 

intake of over 4.5 billion people in about 94 developing countries in the world (Oyewo, 2011). 

Due to its wide geographic and climatic adaptability, maize is successfully cultivated across 

various agro-ecological zones (temperate zones, sub-tropical zone, and tropical zones) globally, 

especially in Latin America and sub-Saharan Africa (SSA) (Ranum et al., 2014). 

 
 

In SSA, maize is the most important cereal crop, and it provides food and livelihood means for 

more than 300 million smallholder farmers (Mathenge et al., 2014). It is cultivated on 

approximately 37 million hectares in SSA (Hruska, 2019). A large proportion of maize produced 

in SSA is used as human food albeit processed into various forms (Badu-Apraku and Fakorede, 

2017). The immature field maize (green maize) is normally eaten as a snack after boiling or 

roasting as corn on the cob (Badu-Apraku and Fakorede, 2017). The dried maize grains are milled 

and consumed as a starchy base in the form of porridge, gruels and soups. Maize is also a key 

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constituent in animal feeds and serves as raw materials in industrial products, including the 

production of biofuels (Shiferaw et al., 2011). 

 
 

The nutritional composition of maize, include high amounts of carbohydrate (mostly as starch or 

sugar) and low quantities of proteins, lipids, vitamins, and minerals (Ranum et al., 2014). It is a 

vital source of all the dietary requirements accounting for about 20% of the basic calorie intake of 

50% of the population in SSA (Badu-Apraku and Fakorede, 2017). Due to its dietary importance, 

agricultural policies favouring the promotion of a steady supply of maize through increased 

productivity have been developed in Africa to improve the value chain (Thorne et al., 2002). 

However, several abiotic and biotic factors such as poor climate conditions, declining soil fertility, 

socio-economic constraints, pests, and diseases have increased in recent years, thus exemplifying 

the severe constraints on maize production in SSA. The impacts of pests are particularly severe on 

impoverished smallholder farmers in rural areas who rely solely on agriculture for their food and 

means of livelihood. 

 
 

Among the abundance of arthropod pests significantly threatening maize production in Africa, 

such as the African sugarcane stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae), the 

African pink borer Sesamia calamistis Hampson (Lepidoptera: Noctuidae), maize leafhopper 

Cicadulina mbila Naude (Hemiptera Cicadullidae), a potential vector of the maize streak virus, the 

maize stalk borer Busseola fusca Fuller (Lepidoptera: Noctuidae), and Chilo partellus Swinhoe 

(Lepidoptera: Crambidae), the fall armyworm Spodoptera frugiperda J.E. Smith (Lepidoptera: 

Noctuidae), an invasive pest, is currently the most damaging (Tambo et al., 2020), and there is no 

apparent sign of it abating. 

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In SSA, the annual economic losses in maize yield attributed to S. frugiperda has been estimated 

at US$ 2.5 - 6.2 billion (Abrahams et al., 2017; Day et al., 2017). Since the first report of this pest 

in Ghana, in 2017, annual yield losses in maize have been estimated at US$ 177 million 

(Rwomushana et al., 2018). The application of chemical pesticides is the main method used for 

the control of S. frugiperda in Ghana and across SSA (Rwomushana et al., 2018), and Asia (Tambo 

et al., 2020). However, over-reliance and irrational use of these chemicals have resulted in the 

development of resistance in the pest, thus exacerbating its impacts (Carvalho et al., 2013). The 

implications of these are severe, because of the significant increases in management costs resultant 

from the development of new classes of insecticides and higher frequencies of application required 

(Tambo et al., 2020). Furthermore, the indiscriminate use of insecticides is a threat to 

environmental health and ecosystem functioning due to its inimical effects on beneficial/non-target 

organisms, including pollinators, pathogens, parasitoids, and predators. This continues to be the 

case to date, hence the need for an integrated pest management approach (Tambo et al., 2020). 

 

 
1.2 Justification 

 

Maize is a primary cereal crop widely grown by most of the smallholder farmers in Ghana 

accounting for over 50% of the total cereal production (Akramov and Malek, 2012). Despite its 

importance in ensuring food security, maize production in Ghana has remained lower than 

expected (IFPRI, 2014). For example, the average maize yields in the country in 2012 was 

estimated between 1.2 - 1.8 metric tons (Mt) per hectare (ha), as against an expected potential yield 

of 4 - 6 Mt/ha (IFPRI, 2014). This was also the case in 2016 where 1.99 Mt/ha was recorded against 

the potential average yield of 5.5 Mt/ha (MoFA, 2017). The low productivity in maize yield can 

be attributed to several factors such as drought, low soil nutrients, unfavourable climatic 

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conditions, poor agronomic practices, diseases and pests’ infestations of which S. frugiperda has 

become the most destructive. 

 
 

Evidently, the impact of S. frugiperda in Ghana is alarming and the main management response 

(i.e., the application of pesticides) adopted by farmers have proven ineffective, justifying the need 

for the development of integrated pest management (IPM) strategies against the pest (Tambo et 

al., 2020). Globally, there is consensus on the use of IPM; a strategy that aims to preserve the 

integrity of functioning ecosystems by conserving and promoting the natural mortality factors of 

pests through the combination of multifaceted pest management methods in a compatible manner 

for the management of agricultural pests (Stern et al., 1959; Barzman et al., 2015). Therefore, 

biological control, that is the use of natural enemies including parasitoids, predators and 

entomopathogens for the suppression of pest populations below levels of economic and ecological 

significance is generally considered as an effective and long-term control strategy for managing 

invasive insect pests and a proven alternative to the use of synthetic insecticides (Agboyi et al., 

2020). 

 
 

In contributing to S. frugiperda IPM in Ghana, the aim of the research reported in this thesis was 

to investigate the role of different management practices on the diversity and abundance of 

arthropod predators and other arthropod communities in the maize agroecosystems. It also sought 

to understand the potential of R. bicolor as a biological control agent of S. frugiperda in Ghana. 

Studies on this predator (i.e., R. bicolor) was recommended by the West African sub-station of the 

Centre for Agriculture and Bioscience International (CABI) and the Plant Protection and 

Regulatory Services Directorate of the Ministry of Food and Agriculture (PPRSD/MoFA) after 

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collaborative joint-surveys of natural enemies of S. frugiperda in Ghana in 2018. This thesis is the 

first report of the functional response, efficacy, and potential of R. bicolor for the management of 

S. frugiperda in Ghana, with the rationale of providing relief of the pest to smallholder farmers. 

 

 
 

1.3 Objective 

 

1.3.1 Main objective 

 

The study aimed to investigate the effects of augmentative release of an egg parasitoid and 

insecticide use on the diversity and abundance of arthropods, predators, and Spodoptera frugiperda 

infestation levels in maize agroecosystem in Ghana. Further, it assessed the potential of a 

promising naturally occuring predator, for biological control of S. frugiperda. 

1.3.2 Specific objectives 

 

1. Determine the diversity and abundance of the general arthropod communities associated 

with maize agroecosystems in treatment MFP and the control plots. 

2. Determine the diversity and abundance of the predators as well as Spodoptera frugiperda 

 

infestation levels in BCM, control and MFP plots. 

 

3. Evaluate the potential of the predator, Rhynocoris bicolor as a biological control agent of 

 

Spodoptera frugiperda. 

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CHAPTER TWO 

 

LITERATURE REVIEW 

 
2.1 Origin and distribution of Spodoptera frugiperda 

 

Spodoptera frugiperda is native to the tropical and subtropical regions of the Americas, occurring 

from the farthest south in Argentina to southern Florida and Texas in the north (Nagoshi et al., 

2012; Early et al., 2018). In early 2016, S. frugiperda was detected in Benin Republic, Nigeria, 

São Tomé and Príncipe, and Togo, in West and Central Africa (Georgen et al., 2016). This was 

the first report of S. frugiperda in Africa and outside of its native range (Georgen et al., 2016). 

One year later (i.e., 2017), the pest had spread into 30 countries on the continent (Abrahams et al., 

2017; FAO, 2018a), and by late 2018, 41 of the 54 countries in Africa, including Madagascar had 

been invaded by S. frugiperda (Chinwada, 2018). In 2019, four more countries were invaded by 

the pest, resulting in a cumulative of 45 invaded countries in Africa (Fig. 2.1). Currently, S. 

frugiperda occurs in all sub-Saharan African counties, except Lesotho (FAO, 2019). 

 

 
Figure 2.1: Global occurrence and distribution of Spodoptera frugiperda. 

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In early 2018, S. frugiperda was reported in Asia, following its detection in Karnataka and Andhra 

Pradesh in India (EPPO, 2018; IITA, 2018; Sharanabasappa et al., 2019). Recent reports have 

confirmed the spread of S. frugiperda in 12 other countries in Asia, including Bangladesh, China, 

Japan, Indonesia, Malaysia, Myanmar, Nepal, Sri Lanka, Thailand, Vietnam, and Yemen (FAO, 

2018; Baloch, 2020) (Fig. 2.1). Just recently, in 2020, S. frugiperda was detected on the Australian 

continent (Maino, 2021) (Fig. 2.1). 

 
 

Spodoptera frugiperda was first reported in the Yilo Krobo district of the Eastern region of Ghana 

in 2016 and later in the Volta and Northern Regions in 2017 (Cock et al., 2017). The pest has since 

spread into all maize agroecosystems and agroecological zones in the country (Fig. 2.2). 

 

 
Figure 2.2: Occurrence and distribution of Spodoptera frugiperda in Ghana. 

Source: Rwomushana et al. (2018). 

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2.2 Taxonomic identity, description and biology of Spodoptera frugiperda 

 

2.2.1 Taxonomic identity 

 

Spodoptera frugiperda was previously identified and described as Caradrina frugiperda, 

Laphygma frugiperda Guenee, 1852, Laphygma inepta Walker, 1856, Laphygma macra Guenee, 

1852, Noctua frugiperda J.E. Smith, Phalaena frugiperda Smith and Abbot, 1797, Prodenia 

autumnalis Riley, 1870, Prodenia plagiata Walker, 1856, Prodenia signifera Walker, 1856, 

Trigonophora frugiperda Geyer, 1832. However, the preferred and generally acceptable scientific 

name is Spodoptera frugiperda J.E. Smith. The taxonomic classification of S. frugiperda is given 

below: 

 
 

Kingdom: Animalia 

 

Phylum: Arthropoda 

 

Class: Insecta 

 

Order: Lepidoptera 

 

Family: Noctuidae 

 

Genus: Spodoptera 

 

Species: Spodoptera frugiperda 

 

 

 
2.2.2 Description and biology 

 

Spodoptera frugiperda is a holometabolous pest. Its life cycle has an egg, six instar larvae, pupa, 

and adult stages (Fig. 2.3). In tropical climates, it completes its life cycle in about 30 - 40 days and 

55 days under temperate conditions (Prasanna et al., 2018). Diapause does not occur in S. 

frugiperda. Therefore, like all ectothermic species, all aspects relating to its 

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survival, reproduction, and phenology are completely dependent on climate parameters such as 

temperature and precipitation, as well as availability of host plants, thus a multivoltine pest (i.e., 

overlapping generations occurring in a year) (Abrahams et al., 2017; Prasanna et al., 2018). 

 

 

 

 

 

 

Figure 2.3: Life cycle of Spodoptera frugiperda. Source: Naharki et al. (2020). 

 

 

2.2.2.1 Egg 

 

The egg is dome-shaped with a flattened base and an upward curve at the apex and a broadly 

rounded point (Luginbill, 1928; Capinera, 2000). It is about 0.4 mm in diameter and 0.3 mm in 

height (Fig 2.4). Eggs are pale yellow or cream-coloured at the time of oviposition and become 

light brown prior to eclosion (Luginbill, 1928). Maturity takes about 2 - 3 days between 20 - 30°C. 

Eggs are usually laid in batches, ranging between 150 - 200 eggs which are laid in two to four 

layers deep on the surface of the leaf (Luginbill, 1928; Prasanna et al., 2018). The egg mass is 

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usually covered with a protective layer of grey-pink scales (setae) from the female abdomen. The 

number of eggs per mass varies considerably but is often 100 to 200 and the total egg production 

per female during her entire life cycle averages about 1500 with a maximum of over 2000 

(Luginbill, 1928; Prasanna et al., 2018). Eggs masses may be laid on the underside of the leaves, 

or top of the leaves (Fig. 2.4). In a few cases, particularly on very young crops, eggs may be laid 

on the stem (Luginbill, 1928; Prasanna et al., 2018). The eggs hatch into neonate larvae within 4 

days (Simmons and Lynch 1990; Prasanna et al., 2018). 

 
 

 

Figure 2.4: Eggs of Spodoptera frugiperda. Source: UF/IFAS Extension revised, (2017), 

http://edis.ifas.ufl.edu 

 

 

2.2.2.2 Larva 

 

The larval stage consists of six instars (Pitre and Hogg, 1983). The head capsule widths for the 1st 

 

- 6th instar larvae are averaged at 0.35, 0.45, 0.75, 1.3, 2.0, and 2.6 mm, respectively and attain 

 

lengths of about 1.7, 3.5, 6.4, 10.0, 17.2, and 34.2 mm, respectively (Pitre and Hogg, 1983) (Fig. 

 

2.5). 

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Figure 2.5: Neonate and the six instar larvae stages of Spodoptera frugiperda. 

 

Source: Coverta agriscience, Australia. https://www.corteva.com.au/agronomy-hub/faw.html 

 

 

 
 

The mean development time for each of the six instar larvae has been estimated at 3.3, 1.7, 1.5, 
 

1.5, 2.0, and 3.7 days, respectively at 25 ºC (Pitre and Hogg, 1983). Upon emergence, the first 

instar larvae are greenish with a blackhead and become orange-coloured at the second instar larvae 

stage. The dorsal surface of the body becomes brownish and white lateral lines form at this stage 

(i.e., 2nd instar larvae). The white lateral lines become conspicuous in the third instar larvae. The 

head of the fourth to the sixth instar larvae is reddish-brown, mottled with white, and the brownish 

body bears white sub-dorsal and lateral lines. Elevated spots occur dorsally on the body and are 

usually dark in colour with spines. The head of the mature larva is also marked with a white 

inverted "Y" and the epidermis of the larva is rough or granular in texture when examined closely 

(Oliver and Chapin, 1981). Four black spots in square form occur on the last abdominal segment 

(Pitre and Hogg, 1983). 

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The young larvae (1st - 3rd instars) are usually found in the leaf whorl of young maize plants. They 

feed gregariously, mostly at night, on the underside of maize leaves, resulting in semi-transparent 

patches on the leaves called “windows”. They can spin silken threads that propel them to new host 

plants (Luginbill, 1928; Capinera, 2000). The larvae are often cannibalistic in the second and third 

instar stages, thus only one or two larvae are found per whorl of the maize plant. The older larvae 

(4th - 6th instars) are found in the whorl of the plants where most of its damage occurs resulting in 

ragged holes on leaves. Continuous feeding by larvae can kill the host growing points resulting in 

no new leaves being formed. 

 

 
 

Often only one or two mature larvae are found per plant, as they become cannibalistic when larger 

and feed on each other to reduce competition for food resources (Chapman et al., 1999). They 

produce large frass quantities that resemble sawdust when dried. Mature larvae can eat their way 

through the protective leaf bracts into the side of maize cobs and then feed on the developing maize 

seeds. The duration of the entire larval stage averages about 14 days in sunny seasons and 30 days 

in the wet season, and then drop to the soil for pupation. 

 

 

 
2.2.2.3 Pupa 

 

Pupation normally occurs in soil depths of 2 - 8cm (Pitre and Hogg, 1983). The larva constructs a 

loose cocoon which is about 20 - 30 mm in length by tying together particles of soil with silk. 

Larvae may web together leaf debris and other material to form a cocoon on the soil surface when 

the soil is very hard. The pupa is reddish-brown, measuring about 14 - 18 mm in length and about 

4.5 mm in width (Luginbill, 1928; Capinera, 2000) (Fig. 2.6). The duration of the pupa stage takes 

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about 8 - 9 days during sunny seasons but reaches 20 - 30 days during the wet season (Capinera, 

2017). 

 

 

 

 
 

Figure 2.6: Pupa of Spodoptera frugiperda. 

 

Source: CABI, 2019, Fall Armyworm Handbook: identification and management 

https://www.cabi.org/isc/FullTextPDF/2019/20197200644.pdf 

 

 

 
2.2.2.4 Adult male 

 

The body length of the male is 1.6 cm, while the wingspan measures about 3.7 cm. A mottled 

forewings occur in males (i.e., light brown, grey, and straw). About 75% of the forewing has a 

discal straw coloured cell and the rest contains triangular white spots proximal to the centre of the 

wing (Luginbill, 1928; Sparks, 1979) (Fig 2.7). 

 

 

2.2.2.5 Adult female 

 

The body length of the female is 1.7 cm, while the wingspan measures about 3.8 cm. Ranging 

between an apparent grey-brown to either a brown or grey mottling, the forewings of females are 

less distinctly marked than males (Fig 2.7), and the hind wings are straw coloured albeit with a 

dark-brown margin. The peak of activity of both adults (male and female) occur in warm, humid 

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https://www.cabi.org/isc/datasheet/29810#39070793-05af-42fc-b7ab-3628c75403a1
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evenings, and they are nocturnal species. Almost the entire eggload are laid following a 3-4 days 

of preoviposition. However, egg-laying may continue for about three weeks and the average life- 

span of adults is about 10 days, ranging between 7 - 21 days (Luginbill, 1928; Sparks, 1979) (Fig. 

2.7). 

 

Figure 2.7: Adult female and male Spodoptera frugiperda. 

 

F indicates a female, while M indicates a male. 

 

Source: Integrated Pest Management University of Missouri 

https://ipm.missouri.edu/pestMonitoring/faw/identification.cfm 

 

 
 

2.3 Movement and dispersal 

 

Spodoptera frugiperda is nocturnal and can fly over long distances, encompassing 100 kilometres 

(km) per night (Johnson, 1987; Cock et al., 2017). This innate dispersal propensity facilitates its 

ability to find different habitats and favourable environmental conditions 

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https://www.cabi.org/isc/datasheet/29810#960a98e4-ad3f-4ccc-bda9-c86091d54374
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(Tendeng et al., 2019). Three-day-old moths have the strongest flight capacity and can attain an 

average flight distance, flight duration, and flight velocity of 29.21 km, 11.00 hours, and 2.69 km 

h–1, respectively in 24 hours (Ge et al., 2021). The fast spread of S. frugiperda in Africa has been 

linked to the moth’s notable migratory ability, prevailing wind conditions, and the availability of 

varied host species (CABI, 2019). 

 

 
2.4 Host range of Spodoptera frugiperda 

 

Spodoptera frugiperda is a polyphagous pest but demonstrates a preference for the Poaceae family 

(Casmuz et al., 2010). It is frequently found attacking wild and cultivated grasses, including maize, 

rice, sorghum, and sugarcane. In a recent review by Montezano et al. (2018), S. frugiperda was 

reported to attack 353 host plant species from 76 plant families, principally Poaceae (n = 106), 

Asteraceae (n = 31), and Fabaceae (n = 31). 

 

 
2.5 Damage and impacts of Spodoptera frugiperda 

 

Feeding by the larvae of S. frugiperda on the vegetative and reproductive structures of maize 

(leaves, tassels and ears) causes severe defoliation and reduction in photosynthesis (Abrahams et 

al., 2017). The first instar larvae usually consume the leaf tissues from one side, leaving the 

opposite epidermal layer intact. The second and third instar larvae create holes in leaves and feed 

on the edges of the leaves and then inward. At the seedling and early-whorl stages of maize, 

infestations induce defoliation and apical meristematic damage. Chimweta et al. (2019) and 

Hruska (2019) both argue that defoliated maize leaves caused by S. frugiperda larvae on maize 

seldom exceeds 50%. Their arguments are supported by the innate capacity of the crop to recover 

from leaf damage. In the mid-whorl stage, the plant suffers excessive damage due to the burrowing 

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 B 

 

feeding effects of the fourth to sixth instar larvae of S. frugiperda. The resultant effects are stunted 

growth, deformity, and plant death, thus a decline in the crop population, and substantial yield 

losses thereof. At the tasselling stage, the larvae of S. frugiperda move towards the tassel, causing 

injury and reduced pollen production and fertility. At the post-tasseling stage (the first reproductive 

stage when the ear formation starts), the larvae move to the developing ear to feed on the silks, 

leading to reduced fertilization and hence a reduced number of kernels per ear. A study by Pannuti 

et al. (2016) showed that young maize leaves are suitable for the development and survival of S. 

frugiperda larvae, while mature maize leaves are unsuitable, hence the larvae preference of settling 

and feeding in the ear of the maize, especially the silk tissues. 

 

 

 

 

Plate 2.1: Spodoptera frugiperda feeding damage on maize (A) leaves, (B) whorl, and (C) cob. 

 

Photo credit: Itohan Idemudia 

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Yield losses associated with S. frugiperda damage on maize are significant (Table 2.1). 
 

 

 
 

Table 2.1: Yield losses in maize caused by Spodoptera frugiperda in some African countries, including 

Ghana. 

Country Percentage yield losses (%) References 

Benin 42.8 - 59.5 Adeye et al. (2018) 

Ethiopia 11.9 Kassie et al. (2020) 

Ghana 0 – 40 Houngbo et al. (2020) 

Kenya 32 – 34 Kassie et al. (2020) 

South Africa 26.5 -56.8 Rwomushana et al. (2018) 

Tanzania 10.8 Britz (2020) 

Uganda 0 – 50 Otim et al. (2018) 

Zambia 0 – 50 Abrahams et al. (2017), Houngbo et al. (2020) 

Zimbabwe 11.57 Kansiime et al. (2019) 

 

 

In Africa, maize losses due to S. frugiperda have been estimated at 8.3 to 20.6 million tons, causing 

annual losses of US $2.5 to 6.2 billion (Abrahams et al., 2017; Day et al., 2017). Surveys 

conducted in Ghana and Zambia reported an average yield loss in maize, due to S. frugiperda, as 

26.6% in Ghana and 35% in Zambia, cumulating to an estimated annual loss of US$ 177 million 

in Ghana and US$ 159 million in Zambia (Rwomushana et al., 2018). In addition, to yield 

reductions, some African countries have also incurred significant expenditures on insecticides 

purchase and monitoring. For example, in 2017, the Ghana Government allocated US$ 4 million 

for the purchase of pesticides and education of farmers. Similarly, the government of Zambia 

allocated US$ 3 million to subsidize pesticide and protective clothing purchases. Furthermore, the 

Ugandan Government allocated US$ 7 million for the supply of pesticides to control S. frugiperda 

(Abrahams et al., 2017). Therefore, in the absence of appropriate and effective control strategies, 

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the pest will continue to cause huge destruction to maize production thereby posing a serious threat 

to sustainable food security. 

 

 
2.6 Management of Spodoptera frugiperda 

 

Considering the significant economic impacts of S. frugiperda on maize production in Africa, 

efficient and affordable management practices of the pest for smallholder farmers are required. 

Some of the recommended and widely adopted management practices that minimize damage 

caused by S. frugiperda include cultural control, chemical control, botanicals, (Abrahams et al., 

2017); biological control, push-pull technology, host plant resistance and an integrated S. 

frugiperda management strategy (Prasanna et al., 2018). 

 

 

2.6.1 Cultural control 

 

The cultural control method is an essential management strategy for S. frugiperda as it is the 

starting point to minimize the pest’s population densities prior to the application of other control 

methods. It mainly involves the application of proper agronomic practices that promote and 

strengthen maize agroecosystems, making it less attractive to the pest. Cultural practices that can 

help reduce the prevalence and high risk of infestation of S. frugiperda include the use of clean 

seed varieties (FAO, 2018), early planting (late-planted maize crops are more susceptible to high 

infestations of S. frugiperda than early planted crops) (Assef and Ayalew, 2019). Also, appropriate 

planting depth, regular field weeding, appropriate fertilizer application to improve crop vigour, 

proper irrigation, intercropping - preferably with non-grass species such as cowpea. Furthermore, 

good cultural practices include crop rotation with non-host plants, removal of damaged plants from 

the field, and destruction of all crop residues after harvesting. 

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Other cultural practices that can also be utilized in managing this invasive pest include early and 

regular visual inspection, handpicking, destroying egg masses and larvae of S. frugiperda, 

ploughing soil deeply to expose larvae and pupae to the upper surface of the soil, and putting sand 

mixed with lime or ash in the whorl of attacked maize to kill the larvae (Abrahams et al., 2017, 

CABI, 2017). Kumela et al. (2019) reported that 14% and 39% of the farmers in Ethiopia and 

Kenya practised cultural methods such as handpicking in managing S. frugiperda. In Ghana, 56% 

of smallholder maize growers adopt early planting, while 22%, 7%, 58%, and 24% adopt regular 

weeding, crop rotation, ash or sand, handpicking eggs and larvae of S. frugiperda, respectively 

(Tambo et al., 2020). 

 

 

2.6.2 Chemical control 

 

The chemical control method which involves the application of synthetic insecticides is the most 

adopted method for controlling S. frugiperda (Assefa and Ayalew, 2019). For example, following 

the outbreak of S. frugiperda in sub-Saharan Africa, the emergency response action, to mitigate 

the pest, taken by governments of the affected countries rely solely on chemical pesticides. In the 

surveys conducted by CABI in 2017, in Ghana and Zambia, it was revealed that though 

Cypermethrin was the most used chemical pesticide by farmers in the two countries for the control 

of S. frugiperda, Lambda Cyhalothrin was significantly more effective (Rwomushana et al., 2018). 

Also in Ghana, Emamectin benzoate is considered moderately effective against the pest, while 

most of the farmers who applied Chlorpyrifos deemed it partially effective (Rwomushana et al., 

2018). However, the over-reliance and seldom rationale application of several chemical pesticides 

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with common active ingredients have resulted in the development of resistance in S. frugiperda to 

these chemicals (Fatoretto et al., 2017). 

 
 

The resistance or tolerance mechanisms of S. frugiperda to insecticides comprises of two 

components: the detoxification/metabolic mechanism and the target resistance mechanism (Zhang 

et al., 2020). The increased activity of detoxification metabolizing enzymes is fundamental in the 

pests’ resistance to insecticides (Yu et al. 2003). Detoxification-related gene families such as 

mixed-function oxidases (MFO), glutathione S-transferase GSTs, cytochrome P450 (P450), 

esterases (ESTs), alkaline phosphatase, trypsin, aminopeptidase and chymotrypsin are also 

associated with insecticide resistance and contribute to the invasiveness of S. frugiperda (McCord 

and Yu 1987; Yu et al., 2003; Zhu et al., 2015). 

 
 

Also, chemical insecticides are considered not effective in reducing the populations of S. 

frugiperda due to the polyphagous nature, high reproductive capacity and rapid migratory 

behaviour of the pest (Goergen et al., 2016). Furthermore, some chemical pesticides are highly 

hazardous pesticides posing negative impacts on the environment, human health and natural 

enemies (Bateman et al., 2018; Prasanna et al., 2018). 

 

 

2.6.3 Botanicals 

 

Botanicals are naturally occurring chemicals extracted or derived from plants with insecticidal 

properties. The use of botanicals is usually a preferred alternative to synthetic insecticides, such as 

pyrethroids and organophosphorus that negatively impacts the environment and induce both 

resurgence and resistance of S. frugiperda to the synthetic insecticides (Arya and Tiwari, 2013; 

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Bateman et al., 2018). Some of the extracted botanicals from plants that have been used to 

effectively control insect pests, including S. frugiperda are Azadirachta indica Juss. (Meliaceae), 

Milletia ferruginea (Hochst.) Baker (Fabaceae), Croton macrostachyus Hochst. (Euphorbiaceae), 

Phytolacea docendra, Jatropha curcas L. (Euphorbiaceae), Nicotiana tabacum L. (Solanaceae) 

and Chrysanthemum cinerariifollium (Jirnmci, 2013). Azadirachtin obtained from neem has been 

proven to be effective against S. frugiperda in the Americas. Silva et al. (2015) reported that high 

mortality of S. frugiperda larvae can be obtained by using seed cake extract of A. indica. In a study 

carried out by Martínez et al. (2017), it was observed that the ethanolic extracts of Argemone 

ochroleuca from Papaveraceae family resulted in the mortality of S. frugiperda larvae due to a 

depletion in feeding and retarded larval growth. In Ghana, several products based on azadirachtin 

are already registered for S. frugiperda management and control (Rwomushana et al., 2018). 

 

 

 
2.6.4 Push-pull technology (PPT) 

 

The push-pull technology (PPT) is a control technique that involves intercropping cereal crops 

with a repellent plant (i.e. push plant) such as desmodium, Desmodium uncinatum J. 

(Leguminaceae) that repels insect pests and planting a trap plant (i.e., pull plant) such as Napier 

grass, Pennisetum purpureum Schumach (Poaceae) that is highly apparent and attractive to the 

target pest, acting as a border crop around the intercropped field to enhance the control of pests 

(Midega et al., 2018; Harrison et al., 2019). The PPT has proven to be an effective, affordable, 

climate-smart, and farmer-friendly control strategy for mitigating S. frugiperda populations 

(Haftay and Fissiha, 2020). The volatile chemicals such as (E)-β-ocimene and (E)-4, 8-dimethyl- 

1, 3, 7-nonatriene emitted by the push plants are unattractive to S. frugiperda adults and repels 

them to the pull plant where they lay eggs. When the eggs hatch, the neonates burrow into the pull 

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plant. The pull plant then produces a sticky glue-like substance that traps and kills the young larvae. 

In a field experiment in Ethiopia, PPT treated maize plots significantly reduced S. frugiperda 

infestation as compared to monocropping maize plots (Haftay and Fissiha, 2020). 

 

 

 
2.6.5 Host plant resistance 

 

Plants may evolve resistance to pests through interference with one or multiple aspects of a pest- 

plant interaction by expressing resistance-related traits (Stout, 2014). Because host-plant resistance 

constitutes an integral part of integrated pest management, it explores and encompasses the 

utilization of resistant crop varieties with or without other management strategies, with the 

rationale of mitigating crop yield and quality losses caused by pests (Stout, 2014). For example, 

the mechanism of resistance by some pests to Bacillus thuringiensis (Bt) crops involves the trigger 

of toxins and toxin receptor mutation, as well as immune system regulation (Xiao and Wu, 2019). 

Bt-resistance in S. frugiperda has been poorly understood albeit until recently. Some researchers 

have underscored that resistance to Bt toxin proteins by the pest is due to both the activation and 

mutation of toxin receptors. For instance, Cry1F resistance in S. frugiperda induces down- 

regulated expression of Bt receptor alkaline phosphatase (ALP) (Monnerat et al., 2015; Jakka et 

al., 2016). When the receptor of both Cry1F and Cry1A.105, ABCC2 (ATP-binding cassette sub- 

family C member 2), mutates, cross-resistance to Cry1F and Cry1A.105 occurs (Flagel et al., 

2018). Rodriguez-Cabrera et al. (2010) articulates decline in S. frugiperda sensitivity to Cry1Ca1 

toxin is caused by the down-regulated expression of serine protease. In Brazil and USA delta- 

endotoxins from Bacillus thuringiensis kurstaki have been encoded and commercialized in 

transgenic maize (CABI, 2019). 

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2.6.6 Pheromonal control 

 

The sex pheromone (Z)-9-Tetradecenyl acetate (Z-9-14:OAca) is used for the control of S. 

frugiperda. It is also used for Spodoptera exigua (Lepidoptera: Noctuidae) and Agrotis ipsilon 

exigua (Klun et al., 1996). Mating disruption in S. frugiperda using pheromones is considered a 

possibility due to the successes recorded on S. exigua in which (9Z,12E)-9,12-tetradecadienyl 

acetate released at high concentrations, caused mating disruption in tomato, lucerne and cotton 

fields (Shorey et al., 1994). 

 

 

2.6.7 Biological control 

 

Biological control of pests utilizes living organisms (natural enemies) to reduce the densities oof 

pests below critical economic and ecological thresholds, thus less damaging than if left untreated 

(Eilenberg et al., 2001). Biological control is generally believed to be an excellent alternative to 

chemical control because it is environmentally safe, posing no adverse threat to non-target species, 

thus and sustainable and feasible plant protection option (Assefa and Ayalew, 2019). A wide range 

of natural enemies including parasitoids, arthropod predators and entomopathogens have been 

reported to readily attack the different life stages of S. frugiperda in the Americas and Africa 

(Molina-Ochoa et al. 2003; Bateman et al. 2018; Prasanna et al. 2018, Agboyi et al., 2019, 2020; 

Akutse et al., 2019; Kenis et al., 2019; Koffi et al., 2020). 

 

 

2.6.7.1 Biopesticides 

 

Several recent reports have higlighed the impotance and effectiveness of virus-based insecticides, 

notably, the Baculovirus group, including the multiple nucleopolyhedrovirus (SfMNPV) for the 

control of S. frugiperda (Behle and Popham, 2012; Gómez et al., 2013; Haase et al., 2015). Their 

University of Ghana http://ugspace.ug.edu.gh 

https://www.cabi.org/isc/datasheet/29810#b2cb4cd5-bc2a-47c3-91d7-3bd9b677b443
https://www.cabi.org/isc/datasheet/29810#78e78cf6-1498-49a8-a61b-6143381bb0af
https://www.cabi.org/isc/datasheet/29810#e250eb13-ddd8-41be-bf79-e018eaef51e3


24 

 

 

high host specificity, littlee or no toxic or adverse effects to non-target and beneficial organisms, 

accentuate the importance of biopesticides for S. frugiperda control. There is evidence showing 

that the SfMNPV is specific to S. frugiperda. When S. frugiperda ingests baculoviruses, feeding 

rates declines, and the larvae becomes blemish following skin yellowing (CABI, 2019). 

 
 

Both Beauveria bassiana and Metarhizium anisopliae are effective biopesticides of S. frugiperda 

eggs and second-instar larvae (Akutse et al., 2019). Beauveria bassiana can cause 30% moratlity 

in second-instar larvae, while M. anisopliae causes 79.5 - 87.0% in egg mortalities (Akutse et al., 

2019). Akutse et al. (2019) further documented that when M. anisopliae is combined with some 

other fungal isolates, about 96 % mortality of eggs and larvae of S. frugiperda occurs. Bateman et 

al. (2018) reviewed registered biopesticide products in 30 countries: 11 in the native range of the 

pest and 19 in Africa. A total of 50 biopesticide active ingredients were identified for control of S. 

frugiperda (Bateman et al., 2018) 

 

 

2.6.7.2 Parasitoids 

 

In the Americas, over 150 parasitoid species recorded from 13 families (nine in Hymenoptera and 

four in Diptera) have been reported to attack S. frugiperda (Molina-Ochoa et al. 2003). Among 

them, the egg parasitoids such as Trichogramma pretiosum Riley (Hymenoptera: 

Trichogrammatidae), Trichogramma atopovirilia Oatman and platner (Hymenoptera: 

Trichogrammatidae) and Telenomus remus Nixon (Hymenoptera, Platygastridae), larval 

parasitoids such as Campoletis sonorensis Cameron (Hymenoptera: Icheumonidae) and Chelonus 

insularis Cresson (Hymenoptera: Braconidae) and pupa parasitoids such as Diapetimorpha 

introita Cresson (Hymenoptera: Ichneumonidae) and Ichneumon promissorius are the most 

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promising candidates for classical biological control in Africa and across the invasion range of S. 

frugiperda (Molina-Ochoa et al. 2003; Beserra et al. 2005; Jourdie et al. 2009; Pomari et al. 2013). 

 
 

In Africa, surveys conducted by Sisay et al. (2018) in three East African countries (Ethiopia, 

Kenya, and Tanzania) revealed the presence of four hymenopteran species (Cotesia icipe 

Fernandez-Triana and Fiobe (Braconidae), Chelonus curvimaculatus Cameron (Braconidae), 

Coccygidium luteum (Brulle) (Braconidae), Charops ater Szepligeti (Ichneumonidae) and one 

dipteran parasitid (Palexorista zonata (Curran) (Tachinidae). Except for C. curvimaculatus – an 

egg-larval parasitoid, the others are larval parasitoids (Sisay et al., 2018). These species are new 

associations of the pest that have never been reported in the native range. Among the above 

parasitoids, C. icipe is considered the predominant larval parasitoid in Ethiopia, achieving a 

parasitism rate of 33.8 - 45.3%. In Kenya, P. zonata, is the primary parasitoid of the pest with 

12.5% parasitism, while C. luteum is the most found parasitoid of S. frugiperda in Tanzania, 

having a parasitic capacity of 4 - 8.3% (Sisay et al., 2018). 

 
 

A survey of S. frugiperda natural enemies in maize and sorghum fields between 2017 and 2018 in 

Niger revealed the occurrence of three egg parasitoids: Trichogrammatoidea sp. (Hymenoptera: 

Trichogrammatidae), Trichogramma sp. (Hymenoptera: Trichogrammatidae) and Telenomus sp. 

(Hymenoptera: Platygastridae), one egg-larval parasitoid: Chelonus sp. (Hymenoptera: 

Braconidae), and four larval parasitoids: Cotesia sp. (Hymenoptera: Braconidae), Charops sp. 

(Hymenoptera: Ichneumonidae) and unidentified ichneumonid and tachinid fly (Amadou, et al., 

2018). Surveys conducted in Benin, Cote d’Ivoire, Kenya, Niger, and South Africa indicated the 

presence of an egg parasitoid, T. remus (Kenis et al., 2019). 

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In Ghana, Koffi et al. (2020) reported the occurrence of seven parasitoids species: Chelonus 

bifoveolatus (Szpligeti) (Hymenoptera: Braconidae), Coccygidium luteum (Brull) (Hymenoptera: 

Braconidae), Cotesia icipe (Fernandez) (Hymenoptera: Braconidae), Meteoridea testacea 

(Granger), Bracon sp. (Hymenoptera: Braconidae), Anatrichus erinaceus (Loew) (Diptera: 

Chloropidae), and an undetermined tachinid fly (Diptera: Tachinidae). 

 

 

 
2.6.7.2 Predators 

 

The occurrence of several insect predators of eggs and larvae of S. frugiperda is fundamental in 

managing populations of the pest. Predators of S. frugiperda are often generalists, feeding on 

multiple prey species. Predators including ground beetles (Coleoptera: Carabidae), ladybird 

beetles (Coleoptera: Coccinellidae), earwigs (Dermaptera: Forficulidae, Carcinophoridae) and 

bugs (Hemiptera: Pentatomidae, Anthocoridae, Reduviidae), have been reported to associate with 

S. frugiperda in its native range (Prasanna et al. 2018). For instance, the earwig, Doru taeniatum 

Dohrn (Dermaptera: Forficulidae) has been reported as a promising predator of S. frugiperda in 

Central America (Jones et al., 1988; Lastres, 1990). 

 
 

Similarly in Brazil, the predatory earwig, Doru luteipes (Scudder) (Dermaptera: Forficulidae) 

seems to be the most abundant and efficient in reducing populations of S. frugiperda and 

Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in soybean (Lanza Reis et al., 1988; Cruz 

1992, 1995). Under laboratory conditions, Sueldo et al. (2010) reported the efficiency of the 

earwig, Doru lineare (Eschscholtz) (Dermaptera: Forficulidae) in reducing the abundance of S. 

frugiperda larvae. In India, the adults and nymphs of two native pentatomid predatory bugs, 

Eocanthecona furcellata (Wolff) (Hemiptera: Pentatomidae) and Andrallus spinidens (Fabr.) 

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(Hemiptera: Pentatomidae) were found to be effective predators of the larvae of S. frugiperda in 

organically grown maize (Shylesha and Sravika, 2018). Also, Zeng et al. (2021) investigated the 

predatory capacity, behaviour and functional response of the bug, Orius similis (Hemiptera: 

Anthocoridae) on S. frugiperda in China. Results from the study showed that both females and 

males of O. similis successfully preyed on S. frugiperda eggs, suggesting that the predator may be 

a promising candidate for the biological control of S. frugiperda eggs and first-instar larvae (Zeng 

et al., 2021). 

 
 

Ants (Hymenoptera: Formicidae) are often predators of S. frugiperda larvae and pupae. Perfecto 

(1989) studied the interactions among ants, S. frugiperda, and pesticides in maize systems in 

Nicaragua. From the study, it was reported that ants are important predators of S. frugiperda and 

that the use of pesticides had a negative impact on the population and effectiveness of ants as 

biological control agents of S. frugiperda. When the pupae of S. frugiperda were placed in the soil 

in maize fields, it was discovered from the study that 92% of the pupae were removed within four 

days in fields without insecticide treatments, compared with only 4% in fields with insecticidal 

treatments. 

 
 

Assassin bugs (Hemiptera: Reduviidae) is a large family of true bugs that are considered 

economically important taxa due to their important group of generalist predators associated with 

various agricultural pests. They are polyphagous, feeding on prey at higher densities (Ambrose, 

2003). In Africa, assassin bugs have been seen attacking and killing larvae of S. frugiperda in 

maize fields. For example, Koffi et al. (2020), reported the presence of three predators (one species 

of ant and two species of assassin bugs) namely, Pheidole megacephala (F.) (Hymenoptera: 

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Formicidae), Haematochares obscuripennis Stål (Hemiptera: Reduviidae), and Peprius nodulipes 

(Signoret) Hemiptera: Reduviidae) preying on S. fruigerida larvae in maize fields in Ghana. 

Although much is not known of Rhynocoris bicolor, this reduviid predator has been reported as a 

natural enemy of the larvae of Acraea eponina (Cramer) (Lepidoptera: Nymphalidae) in Nigeria 

(CABI, 2019). 

 

 

2.6.8 Integrated management of Spodoptera frugiperda 

 

Integrated pest management is a holistic and flexible control strategy that employs a variety of 

integrated approaches including cultural, chemical and biological control that provides control of 

pests’ populations below economic damage thresholds. Adoption of this management approach 

has the least disruption of the cropping ecosystem, and it is safe for environmental, human, and 

animal health. In managing the S. frugiperda, it is important to consider an integrated approach as 

it is sustainable and prevents the development of pest resistance to chemical pesticides and pest 

resurgence (Orr, 2003). Integrated management of S. frugiperda in farmers’ fields should be 

augmented with effective monitoring, growing healthy plants in a healthy system, conserving 

natural enemies, and training on the application. 

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CHAPTER THREE 

 

MATERIALS AND METHODS 
 

3.1 Field experimental site 

 

The experimental field study (i.e., objectives 1 and 2) was conducted at the Soil and Irrigation 

Research Centre (SIREC) of the University of Ghana in Kpong (Fig. 3.1), during the major maize 

cropping season (May to August) and the minor maize cropping season (August to November) in 

2020. The study location (i.e., Kpong) is situated in the Coastal Savanna agro-ecological zone of 

Ghana – a part of the Accra Plains and it is characterized by a bimodal rainfall pattern (i.e., major 

and minor rainy seasons). Annual average rainfall, temperature, and relative humidity in Kpong 

range between 700 - 1100 mm, 28°C, and 59 - 93 % RH, respectively (Fening et al., 2020). The 

soil type at the experimental site (i.e., SIREC) is the black clayey soil also called vertisol – which 

forms deep wide cracks from the surface downward when dry and becomes sticky when wet with 

a high-water retention capacity (Fening et al., 2020). 

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Figure 3.1: Map of Ghana showing the study site: Soil and Irrigation Research Centre (SIREC) 

of the University of Ghana in Kpong where the field research component of this thesis was 

undertaken from May to November 2020. This original figure was designed and generated in QGIS 

3.16.1. 

 

 
3.2 Experimental design and treatments 

 

The field experiment consisted of two different treatment plots: (i) a biocontrol maize plot and (ii) 

an insecticide application maize plot. A control maize plot (i.e., without treatments i or ii) was 

included. Four replicates of each of the treatments and control were made in a Randomised 

Complete Block Design (RCBD), giving a total of 12 maize plots. The biocontrol, control and 

insecticide plots each measured 0.5 hectares. Each plot had a minimum distance of 200 metres 

apart. The two field treatments and control are delineated further below: 

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i. Biocontrol maize plot (BCM): The treatment applied in this plot was the egg parasitoid, T. 

remus. Augmentative releases of the egg parasitoid were made in the four replicated plots, 

a total of 45,000 parasitized eggs of FAW by T. remus were released per biocontrol plot. 

ii. Maize plot with farmer’s practice (MFP): The treatment applied in this plot was 

insecticides (an Emamectin benzoate-based product, Ataka Super EC®: Emamectin 

benzoate 19.2 g/l) used by local farmers, 

iii. Untreated maize plot (control): no release of T. remus or insecticide application. 
 

 

 

 
Table 3.1: List of the experimental plots and their GPS coordinate in the experimental 

 

field site at SIREC 

Experimental plots Replicates GPS Coordinate 

BCM 1 6°07ˈ48.6ˈˈN 0°04ˈ10.2ˈˈE 

BCM 2 6°08ˈ09.2ˈˈN 0°04ˈ35.7ˈˈE 

BCM 3 6°08ˈ04.9ˈˈN 0°04ˈ54.3ˈˈE 

BCM 4 6°07ˈ53.2ˈˈN 0°04ˈ41.3ˈˈE 

MFP 1 6°08ˈ11.2ˈˈN 0°04ˈ44.4ˈˈE 

MFP 2 6°08ˈ09.8ˈˈN 0°04ˈ41.6ˈˈE 

MFP 3 6°07ˈ48.6ˈˈN 0°04ˈ25.3ˈˈE 

MFP 4 6°08ˈ09.8ˈˈN 0°04ˈ41.7ˈˈE 

Control 1 6°07ˈ59.6ˈˈN 0°04ˈ36.6ˈˈE 

Control 2 6°07ˈ59.6ˈˈN 0°04ˈ36.0ˈˈE 

Control 3 6°07ˈ58.4ˈˈN 0°04ˈ40.7ˈˈE 

Control 4 6°07ˈ50.6ˈˈN 0°04ˈ37.3ˈˈE 

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3.3 Land preparation and maize cultivation 

 

In the BCM treatment and control plots, a tractor was used in ploughing and harrowing the land 

before maize seeds were planted. However, no-tillage was made on the MFP plots. The maize 

variety, Obatanpa which is widely cultivated by farmers in Ghana, was planted in all experimental 

plots. In the major and minor maize cropping seasons, maize seeds were planted on 29th April 2020 

and 30th September 2020 in the BCM and control plots, respectively. Planting on the MFP plots, 

however, occurred on 6th May 2020 in the major maize cropping season and 23rd September 2020 

in the minor maize cropping season. In the BCM and control plots, maize seeds were sown with 

the following layout: 2 maize plants per hole/hill, with a spacing of 40 cm along rows and 80 cm 

between rows. However, in the MFP plots, 2 or 3 maize seeds each were planted by the farmers 

per hole/hill, with a spacing of 40 to 70 cm along rows and 80 to 100 cm between rows. 

 

 
3.4 Weed management 

 

Prior to planting in the BCM and control plots, weeds were managed by applying a pre-emergent 

weedicide, Agristomp 500E: Pendimethalin 500 g/l, using a calibrated 15 litres capacity knapsack 

sprayer. Following maize germination, weeding was done manually once in two weeks in both 

cropping seasons (i.e., major and minor cropping seasons). In the MFP plots, a different pre- 

emergence weedicide; Sunphosate 360 SL: glyphosate 360 g/l was applied before sowing using a 

calibrated 15 litres capacity knapsack sprayer. Thereafter, a selective weedicide (Super Nicogan 

800 WDG: 570 g/kg Maesotrione + 230 g/kg Nicosulfuron) was applied after germination. The 

first application of the selective weedicide was done 3 to 4 weeks after the application of the 

emergence weedicides and the second application was done at the tasseling stage of the crop. 

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3.5 Fertilizer application 

 

Ten days after planting in all treatment and control plots, in both cropping seasons, NPK 20:10:10 

 

+ 3S fertilizer was applied in an amount of 60 kg/ha of the nutrients N, P2O5, and K2O. A second 

fertilizer application, 30 kg/ha of urea 46% N, was applied to all plots 6 weeks after sowing in 

both cropping seasons. In the BCM and control plots, the fertilizer was applied into small holes 

(about 7-10 cm) near individual maize plants. However, in the MFP plots, the fertilizer was 

broadcast on the soil surface in proximity to the maize plants. 

 

 
3.6 Insecticide application 

 

The insecticide applied on the MFP fields was an Emamectin benzoate-based product (Ataka Super 

EC®: Emamectin benzoate 19.2 g/l), which is a common and effective insecticide used by farmers 

for the control of S. frugiperda in Ghana. In both cropping seasons, the insecticide was applied 

once using a calibrated 15 litres tank capacity knapsack sprayer fitted with a fine plastic hollow 

cone nozzle at the manufacturers recommended dose of 15ml/15liters of water. This was done 

during the vegetative stage of the crop. However, no insecticide was applied in the BCM and 

control plots. 

 
 

3.7 Data collection 

 

3.7.1 Field sampling and data collection 

 

Field sampling and data collection (i.e., sampling for arthropods, including predators, and 

infestation levels of S. frugiperda) began two weeks after planting and was sustained for six weeks 

per season in each plot. Sampling was conducted weekly from 8th May to 12th June 2020 and 19th 

October to 23rd November in the major and minor maize cropping seasons, respectively. 

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a b 

c 

3.7.1.1 Sampling for general arthropods 

 

The sampling for arthropods was conducted in the MFP and control plots using yellow sticky traps 

(10 cm×20 cm) purchased from Matrix Innovation Company, Accra. The traps were affixed in five 

sampling points, in a stratified ‘X pattern’ sampling area, in the MFP and control plots to avoid 

border effects (Wyckhuys and Neil, 2006). The yellow sticky traps were affixed on both sides 

using short slender lines on two 2.03 m pegs proximal to maize plants. The pegs were hammered 

into a ground depth of 0.30m, thus leaving 2 m above ground. The traps were affixed at a height 

on the pegs corresponding with the heights of the maize plants (Plate 3.1). However, the traps were 

intermittently adjusted upwards as the maize plants grew taller. 

 

 

 

Plate 3.1: Experimental field with (a) affixed sticky traps in the field, (b) trap positions in the field, 

and (c) trap catches. 

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Traps were collected and replaced weekly. Collected samples were immediately placed in 

colourless polythene bags (Ziploc bags), labelled, and preserved under laboratory conditions. This 

process maintained the integrity of the samples, thus preventing trap/samples damage before 

identification. The traps were not placed in the BCM plots to avoid trapping the released T. remus 

which was introduced intermittently through augmentative releases. 

 

 

3.7.1.2 Sampling for arthropod predators 

 

The sampling for predators of S. frugiperda in the BCM, control, and MFP plots was conducted 

once weekly, from 6 am to 10 am (morning sampling event) and from 4 pm to 6 pm (evening 

sampling event). In both treatment and control plots (i.e., BCM, control, and MFP), 15 maize 

plants occurring in each of the five sampling points in the stratified sampling area (i.e., the ‘X 

pattern’) were randomly selected and sampled (Fig. 3.2). This yielded a total of 75 sampled maize 

plants per plot. 

 

 

 

 
 

Figure 3.2: Schematic design showing the sampling points and the number of sampled maize 

plants in the stratified sampling (i.e., the ‘X pattern’) method. MPs = Maize plants. 

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Visual counts of predators occurring on the plants within the stratified sampling area (“X” pattern) 

including those preying on the eggs and larvae of S. frugiperda were made and predators were 

collected with either a pair of forceps or an insect aspirator. Collected samples (i.e. the predators) 

were then coded using different morphological keys to ease the sorting out, stored in 70% alcohol 

in labelled plastic tubes, and transported to the laboratory for proper identification. Also, some of 

the collected predators were sampled from other points in each of the experimental plots and were 

kept in aerated transparent plastic cups (650 ml) and taken to the SIREC laboratory where they 

were introduced to the egg masses and larvae of S. frugiperda under laboratory conditions. Egg 

masses and larvae of S. frugiperda were separately placed in petridishes (diameter 8.5cm, height 

1.3cm) using a camel brush and some of the collected predators were introduced under 

laboratory environmental conditions (Temperature max/min: 32.7°C/26.7°C; R.H max/min: 

79%/36%) to investigate their potential for control. 

 

Plate 3.2: Visual examination of maize plants in the sampling area (“X” pattern) for predators of 

the S. frugiperda. 

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3.7.1.3 Assessing infestation levels of Spodoptera frugiperda 

 

The same number of maize plants (n = 15) in the same sampling points (i.e., five points) in the 

same stratified sampling area (i.e., the ‘X pattern’) in all treatment and control plots (i.e. BCM, 

control, and MFP), described above (Fig. 3.2) were used to assess the infestation levels of S. 

frugiperda. Here, egg batches and larvae of S. frugiperda in the sampling area were collected, 

counted and then recorded. 

 

 

3.7.1.4 Meteorological data 

 

Temperature and rainfall data were recorded daily from the SIREC weather station and were 

examined to determine their influence (if any) on seasonal infestation levels of S. frugiperda and 

the abundance of predators. 

 
 

3.7.2 Arthropod identification and laboratory assays 

 

3.7.2.1 Identification 

 

The collected samples from the field (i.e., arthropods, including predators) were morphologically 

identified to species level using an insect taxonomic identification key guide, under a 

stereomicroscope provided by CABI at PPRSD in Pokuase, and with the guidance of an insect 

taxonomist. Also, ten (10) samples of the predator species were preserved in 70% ethanol and sent 

to CABI Switzerland where they were morphologically identified and confirmed by a renowned 

entomologist, Dr, Marc Kenis. All identified groups (i.e., order and family, and species) were 

recorded in a data recording notebook and then transcribed to Microsoft excel sheets for analysis. 

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3.7.2.2 Potential of the predator, Rhynocoris bicolor as a biological control agent of 

 

Spodoptera frugiperda 

 

Following the recommendation to evaluate the potential of R. bicolor as a biological control agent 

of S. frugiperda by CABI and PPRSD/MoFA, the functional response of the predator was 

determined in laboratory assays. To do this, vibrant colonies of both the pest and predator were 

first reared and maintained at the PPRSD biocontrol laboratory in Pokuase. Approximately seven 

generations of R. bicolor had been reared in the laboratory prior to this study. Environmental 

conditions in the laboratory were maintained at 27 ± 1 °C and 60 ± 10% RH. 

 
 

Fifty pupae of S. frugiperda were collected from the insectary of the Biotechnology and Nuclear 

Agriculture Research Institute (BNARI), Ghana Atomic Energy Commission (GAEC), Accra. The 

pupae were collected in an aerated transparent plastic jar (500ml) and taken to the PPRSD 

biocontrol laboratory. Emerging adult moths were transferred into another set of transparent 

aerated plastic insect rearing cages. The adults were then provided with a 10% honey-water 

solution marinated in cotton wool. Two freshly collected young maize leaves were excised and the 

distal ends were plugged into cotton wool balls – soaked in water – and inserted into small vials. 

The vials, mimicking potted maize plants, were then placed in each cage to serve as the substrate 

for oviposition. The potted plants were replaced daily and checks for egg masses were made. The 

eggs were incubated in aerated transparent plastics boxes (650ml) containing a piece of dry tissue 

paper for moisture absorption. Following hatching, the larvae were fed with maize or castor leaves, 

depending on the availability of each of the host plants. Over 50 newly emerged larvae were reared 

together in each rearing container. However, at the second instar larvae stage, only five were placed 

together to prevent cannibalism. 

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Plate 3.3: Laboratory set-up for rearing Spodoptera frugiperda. 

 
 

Following the establishment of the laboratory S. frugiperda colony, described above, 30 R. bicolor 

adults were collected from the mother colony already established in the PPRSD biocontrol 

laboratory. They were then transferred into transparent aerated plastic insect rearing containers (15 

cm x 13 cm x 9 cm) to allow for ventilation. However, only five male-female adult pairs were 

maintained together in each cage to prevent cannibalism. This is because females can kill and eat 

males when deprived of food (Personal observation in the laboratory). The adults were fed with a 

10% honey-water solution marinated in cotton wool. The rearing containers were examined for 

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h 

a b c 

d e  g 

h i j k 

eggs daily, and eggs were collected and then transferred carefully into aerated transparent plastic 

cups (650 ml) until eclosion of the first nymphal instar, approximately nine days after oviposition. 

 

 

 
Plate 3.4: Life stages of Rhynocoris bicolor (a) males and females R. bicolor in the rearing arenas, 

(b) newly hatched eggs of the female R. bicolor, (c) 1st Nymphal stage of R. bicolor, (d) 2nd 

Nymphal stage of R. bicolor, (e) 3rd Nymphal stage of R.bicolor, (f) 4th Nymphal stage of R. 

bicolor, (g) 5th Nymphal stage of R. bicolor, (h) dorsal view of male (i) ventral view of male, (j) 

dorsal view of female, (k) ventral view of female attached with a newly killed S. frugiperda larva. 

 
 

Following the establishment of laboratory colonies of the predator (R. bicolor) and prey (S. 

frugiperda), the functional response of R. bicolor was investigated from January to April 2021 in 

the biocontrol laboratory of the PPRSD with environmental conditions, described above, in rearing 

the predator and S. frugiperda colonies. The feeding responses of all nymphal instars and adults 

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of R. bicolor were tested against all instars of S. frugiperda larvae. Prior to the assays, each of the 

tested R. bicolor predators was starved for 24 h. The different S. frugiperda larval instars were 

each introduced in six different densities: 5, 15, 25, 30, 35, 40, respectively into Petri dishes 

(Diameter 8.5cm, height 1.3cm) using a camel’s hairbrush. Thereafter, one each of the five 

nymphal stages and two adult sexes of R. bicolor was introduced to each of the larval instars and 

densities of S. frugiperda delineated above. After six hours, the predator was removed, and the 

number of larvae alive and dead were recorded. The dead larvae were not replaced. Ten replicates 

were made for each of the prey densities. 

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Plate 3.5: Experimental design and replicates used in assessing the functional response of R. 

bicolor with S. frugiperda as prey in a six-hour assay. 

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𝐢=𝟏 

3.8 Statistical analysis 

 

3.8.1 Relative abundance and diversity 

 

The relative abundance (RA) of all identified arthropod species including predators per treatment 

 

and season were calculated using the expression: 𝑹𝑨 = 
𝑵𝒊 

× 𝟏𝟎𝟎 where Ni = total number of 
𝑵𝒕 

 

individuals of the ith species and Nt = total number of individuals of all species. Thereafter, 

Shannon–Wiener diversity index (H) was used to calculate the diversity of the arthropod species 

including predators among the different treatments and seasons. This was done using the formula: 

𝐒𝐡𝐚𝐧𝐧𝐨𝐧 𝐢𝐧𝐝𝐞𝐱 (𝐇) = − ∑𝐬 𝐩𝐢 𝐈𝐧 𝐩𝐢 where p is the proportion (n/N) of individuals of one 
 

particular species found (n) divided by the total number of individuals found (N), ln is the natural 

log, Σ is the sum of the calculations, and s is the number of species. Shannon's equitability or 

evenness (EH) was then calculated using the formula: H/Hmax where H max = ln (S) = the 

maximum value that H can have for a particular sample, i.e., total even distribution, S = total 

number of species in the sample. 

 

 

3.8.2 Infestation level of Spodoptera frugiperda 

 

To satisfy the assumptions of parametric tests, the count data (i.e., egg batches and larvae density) 

from the BCM, MFP, and control plots were first subjected to Shapiro-Wilk’s and Bartlett’s tests, 

respectively (Bartlett 1937; Shapiro and Wilk 1965). Both tests indicated that the data violated the 

assumptions of parametric tests. Therefore, variations in the egg batches and larvae density 

between treatments (BCM and MFP) and control plots for each of the major and minor cropping 

seasons were subjected to the Kruskal-Wallis H test. Following the indication of a significant test 

(P < 0.05) in each instance, Dunn’s multiple comparisons, with p-values adjusted with the Holm 

method, was used to identify heterogeneous mean ranks. Variations in the overall egg batch counts 

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t t 

and larvae infestation level of the pest recorded in the major and minor maize cropping seasons 

also violated the assumptions of parametric tests. So, the Mann-Whitney-Wilcoxon test with 

continuity correction was used to test for significance in variations. 

 

 

3.8.3 Predation rate and functional response of Rhynocoris bicolor 

 

Two different steps, described by Juliano (2001), were used in disentangling the functional 

response of R. bicolor. The first phase was the determination of the type and estimation of the 

parameters of the functional response curve. Fundamentally, identification of the functional 

response type, using a proper model, is crucial for calculating functional response parameters such 

as attack rate and handling time. The response type of R. bicolor was investigated by applying a 

logistic regression of the proportion of prey eaten as a function of the initial prey density offered 

to the predator. A polynomial logistic regression equation assuming a binomial distribution of data 

to define the type of functional response (Juliano, 2001) was fitted as in equation 1 below: 

Na = exp (P0 + P1 Nt + P2 N2 + P3N3 ) 
Nt 1+exp (P0+P1Nt+P2Nt2+P3Nt3) 

 

 

 

where Nt is the initial prey density, Na is the number of prey eaten, and Na/Nt is the probability of 

being eaten. P0, P1, P2, and P3 are the intercept, linear, quadratic, and cubic coefficients, 

respectively. Maximum likelihood was used in calculating the coefficients. The nature of 

functional response – type II or type III – was obtained by the values of the linear and quadratic 

coefficients. When the value of a linear parameter is negative, the functional response is described 

as type II. However, if the linear parameter is positive with a negative quadratic coefficient, then 

the response is delineated as type III. The type II response shows that the proportion of prey 

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45 

 

 

consumption decreases as the prey density increases, while the type III response indicates that the 

proportion of prey consumed increases until an inflection point and then decreases. 

 
 

Following the determination of the functional response type of each of the different life-stages of 

 

R. bicolor, the second phase was initiated to determine the functional response parameters of each 

of these stages. To do this, the data were fitted to the Rogers’ type II random predator equation, 

using non-linear least square regression, because prey was not replaced during the entire 

experiment (Rogers, 1972). The random predictor model was used to calculate the attack rate (a) 

and handling time (Th) of each of the different life-stages of R. bicolor as given in equation 2 

below: 

Na = No [1 − exp (a (Th Na – T ) ) ] 
 

 

 

Where Na is the number of prey eaten, No is the initial prey density (prey.arena−1), a is the attack 

rate (arena.hour−1), Th is the handling time (hour.prey−1), and T is time available for predator 

during the experiment (6 h). Here, the logistic regression and the response parameters (at