Determinants of spatiotemporal dynamics of maize pests.
En charge des activités suivantes:
En charge du suivi d’une dizaine de colonies sur le site de Gif-sur-Yvette. En lien avec l’équipe de Jean-Christophe Sandoz, production de reines, mâles et ouvrières.
En lien avec Lionel Garnery, suivi des ruchers du CANIF (Cernay, Bullion, Rochefort).
Extraction du miel et entretien du matériel ( ruches et miellerie).
Avec l’équipe de Laure Kaiser-Arnauld, participation au suivi d’élevage des sésamies.
Postdoctoral consultant at ICIPE in Data Management, Modelling and Geoinformation Unit
Main responsibility: Implement a project on: “Measuring and modelling crop yield losses due to insect pests under a warming climate”
- Develop a system dynamics model of the population dynamics of insect pest in cropping agroecosystems,
- Design and conduct experiments on temperature and CO2-dependent potential of insect pest to damage the host plant into phytotron,
- Design and conduct experiments on damage-dependent yield losses into greenhouse,
- Develop models with a process-based dynamic modelling (insect pest phenology and crop models),
- Test, evaluate, and analyse the models for future predictions:
- formulate and fit the damage functions representing the conversion of insect injury into yield loss,
- formulate and fit the loss function converting injury into economic losses,
- evaluate the developed model by comparing simulation outputs against observed datasets,
- estimate the applicability of the model to new environmental conditions through comparison of the behaviour to key factors and processes.
- Develop methodological approach for predicting and mapping the phenological adaptation of tropical cereal crops (maize) using multi-environment trials,
- Train on system dynamics modelling,
- Supervise/assist under- and postgraduate students and technicians.
Sokame, B.M., Ntiri, E., Ahuya, P., Torto, B., Le Ru, B.P., Kilalo, D.C., Juma, G., Calatayud, P.-A. (2019). Caterpillar-induced plant volatiles attract conspecific and heterospecific adults for oviposition within a community of lepidopteran stem borers on maize plants. Chemoecology, 29, 89-101.
Sokame, B.M., Rebaudo, F., Musyoka, B., Obonyo, J., Mailafiya, D.M., Le Ru, B.P., Kilalo, D.C., Juma, G., Calatayud, P.-A. (2019). Carry-over niches for lepidopteran maize stemborers and associated parasitoids during non-cropping season. Insects, 10, 191, doi:10.3390/insects10070191.
Sokame B.M., Rebaudo F., Malusi P., Subramanian S., Killo D.C., Juma G., Calatayud P.-A. (2020). Influence of Temperature on the Interaction for Resource Utilization between Fall Armyworm, Spodoptera frugiperda(Lepidoptera: Noctuidae) and a Community of Lepidopteran Maize Stemborers Larvae. Insects, 11, 73. doi:10.3390/insects11020073.
Sokame B.M., Subramanian S., Kilalo D.C., Juma G., Calatayud P.-A. (2020). Larval dispersal of the invasive fall armyworm, Spodoptera frugiperda, the exotic stemborer Chilo partellus, and indigenous maize stemborers in Africa. Entomologia Experimentalis et Applicata, 168, 322–331.
Sokame B.M., Obonyo J., Sammy E.M., Mohamed S.A.,Subramanian S., Kilalo D.C., Juma G., Calatayud P.-A. (2020). Impact of the exotic fall armyworm on larval parasitoids associated with the lepidopteran maize stemborers in Kenya. BioControl, https://doi.org/10.1007/s10526-020-10059-2
Sokame B.M., Tonnang H.E.Z., Subramanian S., Bruce A.Y., Dubois T., Ekesi S., Calatayud P.-A. 2021. A system dynamic model for pests and natural enemies interactions. Scientific Reports, 11, 1401, https://doi.org/10.1038/s41598-020-79553-y
Title of the PhD: Mechanisms of resistance in the African maize germplasm to the fall armyworm, Spodoptera frugiperda (J.E. Smith)
Abstract: Maize (Zea mays L.) is the third largest crop in the world after rice and wheat. In Africa, it is the most important food crop in terms of area harvested and alone provides more than 30% of the total calories of the human population in sub-Saharan Africa. The fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), a pest of maize native to the Americas was first reported in West Africa in 2016, is severely threatening food security in sub-Saharan Africa through the loss of tens of millions of tons of maize production each year according to FAO’s 2018 estimates. In the African context where the majority of maize producers are smallholder farmers with limited access to knowledge and adequate inputs to properly manage this new pest, the use of resistant varieties of the host, obtained either through conventional plant breeding methods or through silica induction (a known inducer of resistance in Grasses against pests), is therefore one of the most effective means of control, compatible with other integrated pest management strategies. The first step is to check whether an increase in the silica content of maize disrupts the development of S. frugiperda larvae. While silica induces a significant increase in stem diameter and height of potted maize plants, it has no influence on the development and mortality of S. frugiperda, ruling out the use of silica in maize resistance to this pest. Some resistant maize varieties have been bred and exist in the Americas against S. frugiperda but none are currently available as they are not adapted to the African continent. The other main objective of this thesis is therefore to develop a strategy to control S. frugiperda in Africa by using resistant varieties derived from African maize germplasm. The first results of the work on breeding and genetic improvement of (sub)tropical maize varieties against S. frugiperda, initiated by the International Maize and Wheat Improvement Center in Kenya (CIMMYT) between 2018 and 2019, indicate that five maize lines out of 1303 genotypes tested in greenhouses under artificial infestation have appreciable levels of resistance to S. frugiperda based on leaf and ear damage. After obtaining hybrids from these lines that are potentially resistant to S. frugiperda, this research is divided into three steps: 1) identify the mechanisms of S. frugiperda resistance in lines and hybrids selected for their resistance, 2) check whether these resistant genotypes are avoided by S. frugiperda females for oviposition, 3) and finally identify the chemical compounds responsible for resistance.
Titre de la thèse (en anglais): Environmental demogenetics of potato late blight in Colombia
Résumé (en anglais): The potato late blight is known for its part in the Irish potato famine during the 19th century. This disease has been extensively studied ever since. However, despite being one of the most well studied plant diseases in the world it remains one of the biggest threats to global food security. The late blight is caused by the Oomycete Phytophthora infestans. This is an hemi-biotrophic pathogen that infects the economically important crops potato (Solanum tuberosum) and tomato (Solanum lycopersicum).
In Colombia due to the prevalence of this disease and the extended use of susceptible potato cultivars, the main control strategy against this disease is the continuous application of fungicides. This constitutes a major problem because the repeated exposure of P. infestans to these fungicides results in the development of acquired resistance, and the effects on the health of the growers and the increased costs of continuously using fungicides during the growth cycle of the crop.
One way of reducing the continuous use of fungicides that has been practiced with some degree of success is the use of simulation and epidemiological models. These models project the proliferation of P. infestans based on environmental conditions such as temperature and relative humidity. This allows the growers to optimize the use of fungicides by applying them exclusively during the most favorable periods for the late blight development instead of a continuous use.
These models however have a few limitations. First, these do not consider the spatial configuration beyond each individual field. This could be an important addition due to the possibility of P. infestans dispersal between fields. Second, these disregard other possible management strategies and conditions that could be informative for the projection of late blight. And third, these are deterministic mechanistic models which have required decades of study to find the response of P. infestans to a variety of environmental conditions. Even though there have been adaptations of these models to tropical conditions, these models have a limited applicability outside the US because of the differences in environmental conditions and the responses of the different lineages present elsewhere.
Our main goal in this work is to develop an integrative model that considers several sources of information including environmental, epidemiological, genetic and spatial within a Bayesian learning framework. The idea is to start with a simple model that can be calibrated through this approach using collected field data. This would allow us to develop both a model for potato late blight in Colombia which would be continually calibrated with newly collected information, and a generic framework that can be used to develop models for lesser known plant pathogens that could be calibrated relying heavily on the collected field data and not previous mechanistic studies.