During its Annual General Meeting held on 18 November 2021, the icipe Governing Council, which consists of globally renowned scientists, honoured eight outstanding postgraduate scholars, currently undertaking their research at the Centre.

Best published science paper by an icipe scholar

Ayaovi Agbessenou (PhD, Togo)
icipe Mentors – Drs. Akutse K. S., Ekesi S., Subramanian S., and Khamis F. M

Paper: Agbessenou A., Akutse K.S., Yusuf A.A., Ekesi S., Subramanian S. and Khamis F. (2020) Endophytic fungi protect tomato and nightshade plants against Tuta absoluta (Lepidoptera: Gelechiidae) through a hidden friendship and cryptic battle. Scientific Reports 10, 22195. https://www.nature.com/articles/s41598-020-78898-8 IF 4.379

Contribution to Science: The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) which is native to South America, has become an invasive and serious economic pest of tomato and several crops belonging to the Solanaceae family in Africa. In Kenya, tomato crop is the most preferred host plant by T. absoluta with high infestation causing up to 100% yield losses. In addition, nightshade an important indigenous vegetable of nutritional importance in Kenya, is an alternative host plant highly preferred by the pest. Current T. absoluta management strategies heavily rely on the indiscriminate use of synthetic insecticides with adverse environmental and human health effects, as well as increased resistance development. Additionally, conventional synthetic pesticides are not effective against the destructive immature stages of T. absoluta due to their concealed feeding behavior. As a viable alternative to the use of synthetic insecticides, antagonists such as endophytic fungi have been reported to improve crop protection.

Endophytic fungi play an important role as plant growth promoters as well as increase yield, nutrition, and tolerance to biotic and abiotic stresses. A new strategy to achieve this crop protection approach involves “vaccinating” the host plants against insect pests and diseases with endophytic fungi through leaf spraying, soil drenching or seed inoculation. In this study, we demonstrated that when tomato and nightshade seeds get vaccinated/inoculated with the fungal inoculum, the fungus spreads throughout the plant without producing substances that cause an infection to the host cell but induces insecticidal properties which negatively affect the destructive immature stages of T. absoluta. The vaccine/endophyte stimulates the production of secondary metabolites or antibiotics, that triggers a defense mechanism in tomato and nightshade plants, a mechanism known as induced systemic resistance.

We therefore identified three most potent endophytic fungal isolates belonging to Trichoderma,Beauveria and Hypocrea genera (mainly T. asperellum M2RT4, B. bassiana ICIPE 706 and H. lixiiF3ST1) mediating improvement of tomato and nightshade anti-herbivore defense against T. absolutaby reducing adult oviposition, leafmining, pupation and adult emergence. These findings could significantly contribute to the development of new generation endophytic fungal-based biopesticides against this cryptic pest in tomato and other solanaceous production systems. The discovery of these potent endophytic fungal-based biopesticides to manage T. absoluta offers the potential to greatly improve Solanaceae crops production/productivity in a nature-inclusive, circular and economic way, while mitigating the environmental effects on these entomopathogenic fungi when applied in inundative approach. Furthermore, these scientific findings will not only impact tomato and other solanaceous growers’ management approaches against T. absoluta, but also significantly contribute to reducing the misuse of synthetic pesticides, due to the economic importance of the pest and the challenges encountered for controlling it sustainably.

Funding: This research was funded by the African Union (AU) (Tuta-IPM Project, Contract Number: AURG II-2-123- 2018), UK’s Foreign, Commonwealth and Development Office (FCDO) (FCDO Biopesticide Project, B2291A- FCDO -Biopesticides), and BioInnovate Africa Phase I project “Promoting smallholder access to fungal biopesticides through Public Private Partnerships in East Africa” (BA/CI/2017-02 (PROSAFE) through the International Centre of Insect Physiology and Ecology (icipe). The authors gratefully acknowledge the icipe core funding provided by UK’s Foreign, Commonwealth and Development Office (FCDO); Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

University: The scholar is registered at the University of Pretoria, South Africa.

Trizah Koyi Milugo (PhD, Kenya)
icipe Mentors – Drs. Tchouassi D.P and Torto B.

Paper:  Milugo T.K., Tchouassi D.P., Kavishe R. A., Dinglasan R. R. and Torto B. (2021) Root exudate chemical cues of an invasive plant modulate oviposition behavior and survivorship of a malaria mosquito vector. Scientific Reports 11, 14785.  https://doi.org/14710.11038/s41598-14021-94043-14785. IF 4.379

Contribution to science:  Parthenium hysterophorus is an invasive plant that grows in areas prone to flooding. In Kenya, the plant has invaded vast tracts of land in the western part of the country, a high endemic area for malaria. Previous reports had shown the invasive weed to be a preferred nectar source for the malaria vector An. gambiae. However, the potential impact of the plant’s allelochemicals on An. gambiae oviposition and bionomics remain poorly understood. To address this gap in knowledge the current study was designed: The study adopted a comparative research design to compare survival of mosquitoes exposed to the plant allelochemicals to the control groups. The key finding was the observation that larvae exposed to the plant allelochemical parthenin developed two to three days earlier but survived four to five days longer as adults than the non-exposed control. The findings revealed the impact of plant allelochemicals on malaria vector adult survival which has potential implications in malaria transmission.  The results therefore serve as a useful baseline for future investigations into the impact of invasive plant species on disease vectors and thus, open new areas for further research.

Funding: We gratefully acknowledge the financial support for this research by Training of Health Researchers into Vocational Excellence (THRiVE); and International Foundation for Science (IFS) for providing funds for my PhD studies and for this research. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

University: The scholar is registered at Tumaini University, Tanzania.

Rose Nyakemiso Sagwe (PhD, Kenya)
icipe Mentors – Drs. Dubois T. and Lattorff H.M.G

Paper: Sagwe R.N., Peters M., Dubois T., Steffan-Dewenter I.and Lattorff H.M.G (2021) Pollinator supplementation mitigates pollination deficits in smallholder avocado (Persea americana Mill.) production systems in Kenya. Basic and Applied Ecology,  https://doi.org/10.1016/j.baae.2021.1008.1013    IF 3.414

Contribution to science:  Avocado (Persea americana Mill.) is a major horticultural crop that relies on insect mediated pollination. In avocado production, a knowledge gap exists as to the importance of insect pollination, especially in East African smallholder farms. In this study, conducted in a leading smallholder avocado production region in Kenya, we assessed the dependence of avocado fruit set on insect pollination and whether current smallholder production systems suffer from a deficit in pollination services. Furthermore, we assessed if supplementation with colonies of the Western honey bee (Apis mellifera L.) to farms mitigated potential pollination deficits. Our results revealed a very high reliance of avocado on insect pollinators, with a significantly lower fruit set observed for self- and wind-pollinated (17.4%) or self-pollinated flowers (6.4%) in comparison with insect-pollinated flowers (89.5%). We found a significant pollination deficit across farms, with hand-pollinated flowers on average producing 20.7% more fruits than non-treated open flowers prior to fruit abortion. This pollination deficit could be compensated by the supplementation of farms with A. mellifera colonies. Our findings suggest that pollination is limiting fruit set in avocado and that A. mellifera supplementation on farms is a potential option to increase fruit yield.

Funding: German Federal Ministry for Economic Cooperation and Development (BMZ) commissioned and administered through the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) Fund for International Agricultural Research (FIA), Contract No. 81219433 and Project No. 17.7860.4–001.00; The Norwegian Agency for Development Cooperation, the Section for Research, Innovation, and Higher Education, grant number RAF-3058 KEN-18/0005; UK’s Foreign, Commonwealth & Development Office (FCDO); the Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

University: The scholar is registered at University of Würzburg, Germany.

Best science poster by an icipe scholar

Dorcus Omoga (PhD, Kenya)

Poster:  One Health surveillance; Evidence of known and new zoonotic arboviruses circulation in multiple hosts with potential impact to Human

Supervisors: Drs. Rosemary Sang¹, David P. Tchouassi¹, Marietjie Venter², & Prof. Sandra Junglen³.

¹International Centre of Insect Physiology and Ecology, Nairobi, Kenya

²University of Pretoria, South Africa

³Institute of Virology, Charité—Universitätsmedizin Berlin,Germany

Brief Summary: Arboviruses (arthropod-borne virus) are diverse and include zoonotic viruses like Crimean Congo Haemorrhagic Fever Virus (CCHFV), Rift Valley Fever virus (RVFV), and West Nile Virus (WNV) among others, mostly with epidemic potential. They cause diseases ranging from mild febrile illnesses to haemorrhagic and/or encephalitic fevers as well as death in animals and humans, therefore of great public health, social, and economic importance worldwide. In many African countries including Kenya, their impact is undetermined due to paucity of active surveillance, poor disease reporting systems, and lack of appropriate diagnosis leading to more than 90% of cases being undiagnosed or misdiagnosed and therefore treated as other common endemic diseases like malaria in humans and Rift Valley fever in livestock. As a result, the possibility of these viruses circulating unnoticed causing unresolved disease and/or outbreaks both in humans and animals cannot be underestimated.

In this study, we carried out a one health laboratory based cross-sectional survey in Baringo and Kajiado Counties in Kenya involving humans, livestock, and rodents to understand the transmission of arboviruses. Sampling was done at varied times and algorithms of virological methods applied to screen the samples for viruses.  The findings confirm known and unknown arboviruses actively circulating in diverse hosts, highlighting the need for sustained routine surveillance and differential diagnosis in both healthcare facilities and veterinary diagnostic centres, to enhance detection, early warning and combat zoonotic diseases emergence and outbreaks.  The study creates awareness of circulating known zoonotic arboviruses including tick-borne CCHFV and mosquito borne Ngari virus in unusual hosts, rodents, and livestock respectively. Additionally, a new mosquito borne Orbivirus previously not known in Kenya was isolated from cattle for the first time.

Funding: This work was supported by The German Research Foundation (DFG).  The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at University of Pretoria, South Africa.

Tracy Maina (MSc. Kenya)

Poster title: Horizontal Transmission of Plasmodium-Blocking Symbiont Microsporidia MB In Anopheles Arabiensis.

Supervisors: Drs. Jeremy K. Herren and Tullu Bukhari - International Centre of Insect Physiology and Ecology (icipe

Brief Summary: A novel microsporidian (Microsporidia MB), recently isolated from An. arabiensis in regions of Central and Western Kenya., was found to effectively block Plasmodium transmission. Itseffects on wild caught mosquitoes were examined and there were no significant differences between the infected and the non-infected mosquitoes.

We showed that, in addition to Microsporidia MB being vertically transmitted from field mothers to the offspring (45%-100% depending on the Microsporidia density in the female), it is also horizontally transmitted in adults through mating; From infected male to uninfected female transmission rate was 59% and from F1 infected female to uninfected male transmission rate was 33%. Females that acquired Microsporidia MB from infected males were able to transmit to 37% of their offspring. Analysis of the male seminal secretions by qPCR proved Microsporidia MB presence. These results show that Microsporidia MB is transmitted horizontally through mating and has the potential to be a self-sustainable control strategy for malaria. 

Funding: This work was supported by Open Philanthropy (SYMBIOVECTOR Track A) and the Bill and Melinda Gates Foundation (INV0225840).  We also gratefully acknowledge icipe core funding provided by Foreign, Commonwealth & Development Office, and Government of the United Kingdom, Swedish International Development Cooperation Agency (SIDA), Swiss Agency for Development and Cooperation (SDC), Federal Democratic Republic of Ethiopia, and the Kenyan Government. The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at Jomo Kenyatta University of Agriculture and Technology.

Ayaovi Agbessenou (PhD, Togo)

Poster Title: Temperature-dependent modelling approach and spatial prediction reveal suitable areas for deployment of two Metarhizium anisopliae isolates for sustainable management of Tuta absoluta

Supervisors: Drs. Komivi S. Akutse and Fathiya M. Khamis, International Centre of Insect Physiology and Ecology (icipe) and Dr. Abdullahi A. Yusuf, University of Pretoria, South Africa

Brief Summary: We previously demonstrated the efficacy of Metarhizium anisopliae isolates ICIPE 18, ICIPE 20 and ICIPE 665 against adult Tuta absoluta. However, adequate strain selection and accurate spatial prediction are fundamental to optimize their efficacy and formulations prior to field deployment. This study therefore assessed the thermotolerance, conidial yield and virulence (between 15-35 ^oC) of these potent isolates as a prerequisite for the selection of the best candidate biopesticides for sustainable management of T. absoluta. Our findings demonstrate that M. anisopliaeICIPE 18 and ICIPE 20 can successfully and easily be mass produced at low cost that could enable their uptake by private sector for business incubation. In addition, both isolates were found to be more effective against adult T. absoluta based on their efficacy (germination, growth and virulence) against the pest and their tolerance to different temperature regimes. Spatial prediction, an important decision-making approach for effective field deployment, revealed several suitable locations for ICIPE 18 and ICIPE 20 application against T. absoluta in Kenya. Based on temperature and location-specific modelling, ICIPE 18 and ICIPE 20 could therefore be deployed in the field using an autodissemination approach against adult T. absoluta for effective suppression of the pest thereby reducing the misuse of synthetic pesticides.

Funding: This research was financially supported by the African Union (AURG II-2-123-2018) and UK’s Foreign, Commonwealth & Development Office (FCDO) (B2291A-FCDO-BIOPESTICIDE) through icipe. We gratefully acknowledge icipe core funding provided by Foreign, Commonwealth & Development Office, Government of the United Kingdom, Swedish International Development Cooperation Agency (SIDA), Swiss Agency for Development and Cooperation (SDC), Federal Democratic Republic of Ethiopia, and the Kenyan Government. The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at University of Pretoria, South Africa.

Rose Nyakemiso Sagwe (PhD, Kenya)

Poster Title: Pollination efficiency and visitation frequency of avocado (Persea americana) flower insect visitors

Supervisors: Drs. Michael G. Lattorff and Thomas Dubois - icipe

Ingolf Steffan-Dewenter and Marcell K. Peters – University of Würzburg

Brief Summary: Pollination services from insects are critical for higher yield and better fruit quality in avocado (Persea americana Mill.), a crop that significantly depends on insect pollination. Measuring pollinator effectiveness is vital in capturing the relative contributions of different insect taxa to pollination services to identify the essential pollinators. Various insect species attend flowers, but it is unclear how effectively these flower visitors pollinate, a better understanding of the specific contribution of different pollinators to the production of this globally important crop is necessary. In the present study, we tested pollinator efficiency based on pollen deposition after single visits by different pollinator species in avocado flowers and recorded their frequency. The estimated pollination efficiency was highest in honeybees (Apis mellifera), followed by the hoverfly species Phytomia incisa. These two species had both the highest pollen deposition and high pollen grain loads on their bodies. Furthermore, honeybees were the most frequent avocado flower visitors, followed by flies. Our results imply that managed honeybees can be maintained to achieve substantial pollination services for avocado, particularly in areas lacking efficient wild pollinators. Furthermore, we demonstrated that it is possible to estimate the pollination efficiency of flower-visiting insects using a single-visit pollen deposition. This approach can be applied in other crops to determine the pollination efficiency of common flower-visiting insects.

Funding: This research was financially supported by the German Federal Ministry for Economic Cooperation and Development (BMZ) commissioned and administered through the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) Fund for International Agricultural Research (FIA), Contract No. 81219433 and Project No. 17.7860.4–001.00; the  Norwegian Agency for Development Cooperation, the Section for Research, Innovation, and Higher Education, grant number RAF-3058 KEN-18/0005; UK’s Foreign, Commonwealth & Development Office (FCDO); the Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.  The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at University of Würzburg, Germany.

Evanson Omuse (MSc. Kenya)

Poster Title: Safety of Biopesticides on the Honeybee Apis mellifera and African Stingless Bee Meliponula ferruginea

Supervisors: Dr Thomas Dubois and Dr Saliou Niassy (icipe), Dr John Maina Wagacha and Dr George Otieno Ong’amo (University of Nairobi)

Brief Summary: Bees provide pollination services to over 75% of world food crops, in addition to hive products and by-products, which are essential for food and nutritional security. However, insect pests are major threats to agricultural-based food security, prompting the application of chemical insecticides which have partly contributed to the unprecedented declines of bees globally. Biopesticides may be a “soft” option but their impact on bee survival and pollination biology are least investigated. The performance of biopesticides in bee colonies’ conditions as well as in the field (conditions of target pests) can suitably be described by predictive models, including those yet to be tested on fungal-based biopesticides. Therefore, a tiered study was undertaken to screen the non-target effects of biopesticides Metarhizium anisopliae (ICIPE 7, ICIPE 20, ICIPE 62, ICIPE 69, ICIPE 78) and Beauveria bassiana (ICIPE 284) on the honeybee Apis mellifera and the African stingless bee Meliponula ferruginea. In the first part of the study, bees were exposed in a group of 25-30 bees/cage to 10⁸ conidia/mL of biopesticides and their survival was monitored for 10 days. In the second part of the study, these biopesticides were cultured and incubated at a wide range of temperatures (12, 16, 20, 24, 28, 32, 36°C). Their germination and growth at these temperatures were recorded and fitted to eight nonlinear models to quantitatively predict the thermal requirements of these biopesticides. In the third part of the study, Metarhizium anisopliae ICIPE 69 was applied on flowering cucumber crops that were actively foraged by the stingless bee Meliponula ferruginea in the screenhouses. The pollination behaviour (flight activity, foraging activity, survival of bee foragers) and pollination success (fruit set, maturation and weight) were recorded and compared to the control (plots treated with distilled water). This tiered study established that; (1) the tested biopesticides have no effect on bees and can be safely used in bee-resourced agricultural systems, and (2) the cardinal temperature model with inflection (CTMI), Ratkowsky 3 and generalized β function are convenient models for predicting the performance of biopesticides in bee colonies field. Therefore, this study has the following impacts: (i) promoting the application of biopesticides as alternatives to chemical insecticides in pest management practices, (ii) advocating the use of best temperature-dependent models for routinely screening of promising biopesticides and (iii) giving insight for improving food and nutritional security and ecological health by protecting bees for continuous provision of pollination services and hive products.

Funding: This research was financially supported by the German Federal Ministry for Economic Cooperation and Development (BMZ) commissioned and administered through the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) Fund for International Agricultural Research (FIA), Contract No. 81219433 and Project No. 17.7860.4–001.00; UK’s Foreign, Commonwealth & Development Office (FCDO); the Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.  The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at University of Nairobi, Kenya.