Utilisation De Metarhizium flavoviride Gams & Rozsypal Contre les Sauteriaux Dans des Essais Participatifs en Milieu Paysan au Niger

Participatory trials on the use of a mycoinsecticide based on spores of the entomopathogenic fungus Metarhizium Flavoviride were carried out to control grasshoppers on farmers’ plots at Gouré, Niger. The study was conducted in collaboration with the natural resources management project financed by Africare. From a fallow area of about 800 ha, six plots of 5 ha each were selected. Three of these plots were treated with M. flavoviride, strain IM 330189, while the three remaining plots served as controls. An emulsion of the fungus was prepared with 50 g of dry spores mixed with paraffin and ground oil at a ratio of 7:3. This formulation represents a concentration of 2.5×10¹² spores per litre. The mycoinsecticide was applied at the rate of 2 litres/ha with a Micron ULVA sprayer. Immediately after spraying and three days later, two batches of 50 L4 and L5 Oedaleus senegalensis larvae were collected per plot and each batch kept in a separate cage. One of the two cages was kept in the experimental plot, whereas the second one was taken to the station, in order to follow the grasshoppers’ mortality. Cages were checked daily for two weeks starting from the day of fungus application, and insect mortality recorded. Dead insects were transferred into Petri dishes with moistened filter paper to allow the fungus to sporulate from the cadavers. Grasshoppers kept in cages suffered 80% mortality, 12 days after application. Reduction in grasshopper population density between treated and untreated plots was significantly different, but did not convince farmers, as full grown L5 larvae had emerged as adults and began migrating. However, cadavers collected from cages containing insects from treated plots allowed farmers to follow how the fungus sporulates and contaminates healthy grasshoppers. Farmers were interested in the product but were reluctant to buy a slow-acting insecticide.