Africa Regional Postgraduate Programme in Insect Science
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Item Direct and Indirect Infection Effects of Four Potent Fungal Isolates on the Survival and Performance of Fall Armyworm Larval Parasitoid Cotesia icipe(Sustainability, 2023) Chepkemoi, J.; Fening, K.O.; Ambele, F.C.; et al.Fall armyworm (FAW), Spodoptera frugiperda, has recently invaded Africa, where it is seriously threatening food security. Current management methods rely heavily on synthetic insecticides which are harmful to humans, the environment, and non-target beneficial insects. Cotesia icipe was recently identified as a major FAW-associated indigenous parasitoid causing a high parasitism rate on the pest in Kenya. Previous studies have demonstrated the efficacy of Metarhizium anisopliae ICIPE 7, ICIPE 41, ICIPE 78, and Beauveria bassiana ICIPE 621 against FAW. However, limited information is available on the interactions between these potent isolates and C. icipe. This study, therefore, assessed direct and indirect infection effects of these fungal isolates on C. icipe, induced 2nd instar FAW mortality, and parasitism rates of the infected C. icipe. Results showed that when C. icipe were directly exposed to dry conidia of the fungal isolates, ICIPE 7 and ICIPE 41 caused the highest (100%) C. icipe adult mortality seven days post-exposure. Both isolates also induced the highest FAW larval mortality of 55% and 53%, respectively. ICIPE 78 recorded the highest parasitism rates after direct infection. In the indirect exposure (fungal-infected FAW larvae exposed to the parasitoid), 1 × 109 conidia mL−1 recorded high C. icipe adult and FAW 2nd instar mortalities for all fungal isolates. This study provides: an important baseline for effective fungal-based biopesticide development that could also be used in augmentative biological control. However, further studies are warranted to assess the performance of C. icipe in combination with these potent biopesticides in the field.Item First report of the predatory potential and functional response of the red flower assassin bug Rhynocoris segmentarius (Germar), a natural enemy of Spodoptera frugiperda (J.E. Smith)(Biological Control, 2024) Idemudia, I.; Fening, K.O.; Wilson, D.; et al.The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is currently the most devastating invasive arthropod pest of maize in sub-Saharan Africa. Following its first report in Ghana in 2016, control has been reliant mainly on synthetic chemicals. However, biocontrol has been an effective, sustainable, cheaper, and environmentally friendly option for FAW management. We tested the potential of the red flower assassin bug, Rhynocoris segmentarius (Germar) (Hemiptera: Reduviidae) as a natural enemy candidate for augmentative biocontrol of FAW in Ghana by assessing its predatory rate and functional response under labo ratory conditions in Ghana. The feeding responses of the five nymphal instars and adults (female and male) of R. segmentarius were tested against three larvae ages of FAW: (i) < 1 day old or newly emerged (NE), (ii) 2 days old, and (iii) 6 days old, at six different prey densities: 5, 15, 25, 30, 35, and 40, respectively. All life-stages of R. segmentarius successfully attacked, killed, and fed on the larvae of S. frugiperda, and exhibited a Type II functional response. However, the first and second nymphal stages of R. segmentarius did not successfully attack or kill six-day-old FAW larvae. Females had a significantly higher attack rate (7.79 ± 1.01) and the shortest handling time (1.17 x 10–1) than all life-stages. Our results suggest that R. segmentarius is a potential candidate for augmentative biocontrol of S. frugiperda.Item Fertilizer-bioinsecticide synergy improves maize resilience to Spodoptera frugiperda infestation(Crop Protection, 2024) Fiaboe, K.R.; Agnamba, A.O.; Fening, K.O.; et al.Fall armyworm (FAW), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), invasion in Africa has threatened food security. Optimization of plant tolerance and post-infestation recovery are among the management tactics that are being promoted for the integrated management of this pest, but these techniques are poorly studied in sub-Saharan Africa. Our study examined the efficacy of enriched compost, split-NPK fertilization, conventional fertilization, and bioinsecticides on FAW infestation rates, maize plant resilience, natural enemy presence, and grain yield. We found that split-NPK fertilization significantly improved maize plant robustness and reduced FAW incidence and leaf damage in a phenology-dependent manner, leading to higher grain yields. A synergistic effect was observed when split-NPK was coupled with bioinsecticides, resulting in increased populations of natural predators, and specifically the egg endoparasitoid, Telenomus remus (Nixon) (Hymenoptera: Scelionidae). Multivariate analyses confirmed that factors like split-NPK fertilization, bioinsecticide usage, stem circumfer ence, and overall plant robustness are major determinants of maize grain yield. Our results endorse soil fertility management via split-NPK fertilization as an effective cultural control measure against FAW, providing an alternative to synthetic insecticides. These insights set the stage for future research focused on assessing the economic viability of this integrated approach, exploring the integration of split-NPK with alternative in secticides, evaluating environmental impacts, and examining the underlying resilience mechanisms to FAW, among other avenues.Item Bionomic responses of Spodoptera frugiperda (J. E. Smith) to lethal and sublethal concentrations of selected insecticides(PLOS ONE, 2023) Fiaboe, K.R.; Fening, K.O.; Gbewonyo, W.S.K.Since 2016, the invasive insect Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctui dae) from the Americas has made maize production unattainable without pesticides in parts of Sub-Saharan Africa and Asia. To counteract this pest, farmers often resort to the use haz ardous pesticides. This study aimed to investigate botanicals, microbials, and semi-syn thetic insecticides in Ghana for pest control without harming local ecosystems. Under laboratory and on-station conditions, the present study evaluated the acute and sublethal responses of S. frugiperda to: (i) Pieris rapae Granulovirus (PrGV) + Bacillus thuringiensis sub sp. kurstaki (Btk) 5 WP, (ii) Btk + monosultap 55 WP, (iii) ethyl palmitate 5 SC, (iv) aza dirachtin 0.3 SC, (v) acetamiprid (20 g/l) + λ-cyhalothrin (15 g/l) 35 EC, (vi) acetamiprid (30 g/l) + indoxacarb (16 g/l) 46 EC, and (vii) emamectin benzoate 1.9 EC. The results showed that at 96 hours post-exposure emamectin benzoate-based formulation has the highest acute larvicidal effect with lower LC50 values of 0.019 mL/L. However, the results suggested strong sublethal effects of PrGV + Btk, azadirachtin, and ethyl palmitate on the bionomics of S. frugiperda. Two seasons on-station experiments, showed that the semi-synthetic ema mectin benzoate and the bioinsecticide PrGV + Btk are good candidates for managing S. frugiperda. The promising efficacy of emamectin benzoate and PrGV + Btk on the bionomics of S. frugiperda in the laboratory and on-station demonstrated that they are viable options for managing this pest.Item The natural control agents of the fall armyworm, Spodoptera frugiperda in Togo: moderating insecticide applications for natural control of the pest?(Springer Science and Business, 2023) Adom, M.; Meagher, R. L.; Agboka, K.; et al.Although there has been intensive use of insecticides for the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) management, their effects on population reduction and natural enemies’ performance have not been adequately studied. Therefore, this study investigated the diversity and activity of natural enemies under insecticide and insecticide-free applications. Natural enemies were collected annually from 2016 to 2022 from 348 maize farms throughout the West African nation of Togo. The collections included an entomopathogenic nematode, unidentified bacteria from Enterobacteriaceae and Enterococcus, unidentified viruses from Ascoviruses and Baculoviruses, and several fungal species. Parasitoids collected included hymenopteran and dipteran species that attacked eggs and larvae. The collected predators included species in the following families: Anthocoridae, Carabidae, Chrysopidae, Coccinellidae, Forficulidae, Formicidae, Mantidae, and Reduviidae. The parasitism rates were from 14.72% in 2018 to 45.38% in 2022 for egg masses and from 1.32% in 2016 to 41.85% in 2021 for larvae. The parasitism rates were three to four times higher in unsprayed farms than sprayed farms.Item Differential effects of weather, plant phenology and predators on the seasonal variation of aphids on cabbage(Journal of Applied Entomology, 2023) Forchibe, E.E.; Fening, K.O.; Narh-Madey, B.; Afreh-Nuamah, K.; Cobblah, M.A.; Wamonje, F.O.; Carr, J.P.The aphids Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) pose serious threats to the production of cruciferous crops in the tropics. Understanding their population dynamics is important for developing integrated pest management programmes to minimize their damage to crops. This study investigated the effects of climatic factors, natural enemies and plant age on the population dynamics of these pests. The population density of aphids and their natural enemies in 20 cabbage plants, and weather conditions were monitored for five cropping seasons from 2019 to 2021 in two agroecological zones of Ghana (Coastal Savannah and Deciduous Forest zones). The highest population density of L. e pseudobrassicae was recorded in January (dry season) in both agroecological zones, while the highest population density for M. persicae occurred in September (minor rainy season) and August (dry spell) in the Coastal Savannah and Deciduous Forest zones, respectively. The highest aphid densities were noted to occur during periods with low relative humidity and low rain fall. The population density of L. e. pseudobrassicae was significantly negatively related to plant age, air temperature and relative humidity, and positively related to syrphids (Paragus borbonicus) and spiders in the Coastal Savannah zone, while in the Deciduous Forest zone, it was significantly positively related to coccinellids. On the other hand, M. persicae population density was significantly positively related to syrphids and coccinellids in the Deciduous Forest zone. Rainfall negatively affected syrphids in the Coastal Savannah zone, while air temperature positively affected syrphids and negatively affected spiders in the Deciduous Forest zone. Coccinellids had a significant positive relationship with relative humidity in the Deciduous Forest zone. This study provides important insights into the key factors that regulate aphid population densities on cabbage and will support development of timely interventions to manage these pests.Item Farmers’ knowledge and practices on pollination and insecticide use in cocoa farming in Ghana(INTERNATIONAL JOURNAL OF AGRICULTURAL SUSTAINABILITY, 2022) Umeh, B.C.; Avicor, S.W.; Dankyi, E.; Kyerematen, R.ABSTRACT Although evidence of the limiting role of pollination in cocoa production is mounting, concern about the potential harm of insecticides to pollinators is also increasing. However, effort at examining farmer knowledge and practices on pollination and insecticide use aimed at promoting cocoa pollination is limited. This study assessed farmers’ knowledge and practices on pollination and insecticide usage in four cocoa-growing communities (two organic and two conventional) in the Eastern region of Ghana. Data from interviewing cocoa farmers (200) with a structured questionnaire were analysed using various statistical techniques. Less than 50% of the farmers had knowledge of pollination and its influence on yield. Only 1% of the respondents identified midges as pollinators of cocoa, while 11% and 19.5% identified honey bees and ants as pollinator agents, respectively. Less than 50% of respondents believed insecticide application might impact on beneficial insects, including pollinators. Farmers’ responses were highly influenced by farming system, educational background, farmer groups and extension officers. Our findings show that educating smallholder farmers on pollination and judicious insecticide use is crucial in improving long-term cocoa yields. These findings have implications for pest management policies and farmer sensitization on the impact of indiscriminate insecticide application on the environment and pollinators.Item Assessment of impacts of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize production in Ghana(Oxford University Press, 2021) Koff, D.; Kyerematen, R.; Eziah, V.Y.; Osei-Mensah, Y.O.; Afreh-Nuamah, K.; Aboagye, E.; Osae, M.; Meagher, R.L.Spodoptera frugiperda was considered an insect pest only in the Americas until its first report in African countries in 2016. In this study, farmers and agricultural officials in Ghana were interviewed on their perceptions and knowledge of the pest, on infestation and maize yield variations across years, and on management practices. Farms were inspected to determine the infestation level of 100 plants per hectare. Interviews revealed that farmers were familiar with the larval stages of this pest and noticed that the pest occurred throughout the year, but populations of S. frugiperda increased only during cropping seasons. Infestation levels reported by farmers in surveys were much lower in 2018 (30.38%) than in 2017 (80.92%). Farm inspections confirmed that infestation levels were much lower in 2018 (20.90%) than 2017 (73.70%). The belt formed by Guinea Savannah, Transitional Zone, and Semi Deciduous Forest Agro-Ecological Zones (AEZs) recorded the highest infestations while the lowest were observed from the Sudan Savannah and Tropical Rain Forest AEZs. Insecticides were the most commonly used tactic to manage populations of this new pest. Maize yields increased across Ghana between 2013 and 2015 from 1.52 to 1.73 t/ha, decreased between 2015 and 2017 to 1.55 t/ha, and increased to 1.69 t/ha in 2018. The impact of fall armyworm injury to maize production is discussed.Item Assessment of Bacillus thuringiensis and emamectin benzoate on the fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) severity on maize under farmers’ fields in Ghana(Springer, 2021) Koffi, D.; Kyerematen, R.; Osae, M.; Amouzou, K.; Eziah, V.Y.The introduction of fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) into Ghana is a threat to maize production. This study determined the severity of this pest on maize production subjected to Bacillus thuringiensis (Bt), emamectin benzoate (Eb) sprayed and unsprayed farms under farmers’ practices in Ghana. At least one farm per treatment was selected in each Agro-Ecological Zone (AEZ) for data collection throughout the maize phenology during three production seasons. Percent damaged plants and ears were determined, the proportion of feeding damage on leaves and ears was scored, and yields measured on each farm. Ear damage was most severe in the Guinea Savannah Agroecological Zone with a correspondingly lower yield. The highest yield was recorded from the Tropical Rain Forest zone. The damage levels decreased when plants aged, but the scoring of damage level on attacked ears was greater than that on leaves. Maize plant damage was highest with corresponding lowest yields on unsprayed farms compared to sprayed farms which recorded similar results for both insecticides. Bt and Eb based insecticides (applied at 50g/15L H2O/ha and 75mL H2O/ha, respectively) are efective on FAW larvae and are therefore recommended for FAW management in Ghana.Item Pest status, bio-ecology and management of the false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) and its implication for international trade(Cambridge University Press, 2021) Adom, M.; Fening, K. O.; Billah, M. K.; Wilson, D. D.; Hevi, W.; Clottey, V. A.; Ansah-Amprofi, F.; Bruce, A. Y.The false codling moth (FCM), Thaumatotibia leucotreta (Lepidoptera: Tortricidae) is an insect pest which represents an important threat to the production and marketing of a wide range of agricultural crops in the African-Caribbean-Pacific (ACP) countries. The FCM reduces not only the yield and quality of the crop but also as a quarantine insect pest, restricts the trade of susceptible agricultural produce on the international market. In add ition, little research has been conducted in the ACP countries on the bio-ecology and sustain able management of this pest, especially on vegetables for export. Thus, action-oriented research aimed at understanding the bio-ecology of this important pest is essential to achieve effective management. Various management interventions against this pest have been used in some parts of the world, especially in South Africa on citrus. Currently, farm sanitation is regarded as the key management strategy. Exploring and improving on other interventions such as Sterile Insect Technique, monitoring and mass trapping of male moths, augmentative biological control, use of bio-pesticides, protected cultivation and cold treatment may help to mitigate the expansion of FCM into other countries, especially in the European and Mediterranean Plant Protection Organization region where it has become a regulated insect pest since 2014. This review discussed the bio-ecology of FCM and highlighted some of the challenges and opportunities for its effective management and its implication for international trade, especially the export of chillies from the ACP countries into the European Union market which requires strict phytosanitary regulations