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The fall armyworm (FAW), Spodoptera frugiperda is a real threat to food security. It is able to totally destroy the cereal crops in a country. It can cause famine in Sub-Saharan Africa where cereals are subsistence crops. Reported in Africa in 2016, the FAW succeded to colonize 47 countries in one year. Its migration capacities wich are of around 100 km per night can allow it have fully infest a country like Senegal (ca 200 000 km²) in less than a week. The FAW is very difficult to fight because resistant to several insecticides. Invasive species often invade a new environment without their natural enemies, which promotes their multiplication and damage to crops. To estimate the generation number per year and evaluate the impact of biological control of indigenous natural enemies on the FAW, larvae were collected in maize fields and monitored in the laboratory. The results show that the development cycle of S. frugiperda takes 25 days on average, that is to say fifteen (15) generations per year. The study confirms the presence of three species of native natural enemies, a nematode Hexamermis sp. and two Hymenopterans Chelonus sp. and Campoletis sp. detected for the first time in West Africa on FAW larvae. The overall parasitism rate is 25.8%. These native natural enemies are a very promising means of control against FAW populations. The introduction of agricultural techniques to promote the maintenance and the proliferation of the FAW auxiliaries is an alternative to the use of pesticides.

Ants are a very diverse taxonomic group. They display remarkable social organization that has enabled them to be ubiquitous throughout the world. They make up approximately 10% of the world's animal biomass. Ants provide ecosystem services in agrosystems by playing a major role in plant pollination, soil bioturbation, bioindication, and the regulation of crop-damaging insects. Over recent decades, there have been numerous studies in ant ecology and the focus on tree cropping systems has given added importance to ant ecology knowledge. The only missing point in this knowledge is the reasons underlying difference between the positive and negative effects of ants in tree cropping systems. This review article provides an overview of knowledge of the roles played by ants in orchards as functional elements, and on the potential of Oecophylla weaver ants as biological control agents. It also shows the potential and relevance of using ants as an agro-ecological diagnosis tool in orchards. Lastly, it demonstrates the potential elements which may determine the divergent negative and positive of their effects on cropping systems.

22 pagesInternational audienceIn this paper, we classify all (complete) non elementary algebraic solutions of Garnier systems that can be constructed by Kitaev's method: they are deduced from isomonodromic deformations defined by pulling back a given fuchsian equation E by a family of ramified covers. We first introduce orbifold structures associated to a fuchsian equation. This allow to get a refined version of Riemann-Hurwitz formula and then to promtly deduce that E is hypergeometric. Then, we can bound exponents and degree of the pull-back maps and further list all possible ramification cases. This generalizes a result due to C. Doran for the Painleve VI case. We explicitely construct one of these solutions