CONTROL OF GRASSHOPPERS, PARTICULARLY HIEROGLYPHUS-DAGANENSIS, IN NORTHERN BENIN USING METARHIZIUM-FLAVOVIRIDE

Trials on the use of Metarhizium flavoviride Gams and Roszypal conidia in oil-based formulation for the control of grasshoppers, particularl y Hieroglyphus daganensis Krauss, in Malanville, north Benin, are desc ribed. Preliminary work examined sprayer types, application rate, and time of application. In a trial on 4-ha plots with three replicates, M . flavoviride mycoinsecticide application to H. daganensis nymphs resu lted in field population reductions of 70% after 14 days. In samples i ncubated in cages, mortality was higher in the samples taken 3 or 7 da ys after application than in the sample taken immediately after applic ation, indicating the possibility of residual pick-up compared with di rect spray impact in this environment. Significant mortality was still bring observed in samples collected 37 days after application; to inv estigate this further, a method for bioassaying the spore load in the field was developed and used to monitor the spore load in the field. T he possibility that the results indicate the occurrence of secondary i nfections resulting from horizontal transmission of M. flavoviride is discussed.