Trials on the use of Metarhizium flavoviride Gams and Roszypal conidia in oil-based formulation for the control of grasshoppers, particularly Hieroglyphus daganensis Krauss, in Malanville, north Benin, are described. 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 resulted in field population reductions of 70% after 14 days. In samples incubated in cages, mortality was higher in the samples taken 3 or 7 days after application than in the sample taken immediately after application, indicating the possibility of residual pick-up compared with direct spray impact in this environment. Significant mortality was still being observed in samples collected 37 days after application; to investigate this further, a method for bioassaying the spore load in the field was developed and used to monitor the spore load in the field. The possibility that the results indicate the occurrence of secondary infections resulting from horizontal transmission of M. flavoviride is discussed.

Three experiments were conducted to examine the effects of spray applications of a mycoinsecticide against the rice grasshopper, Hieroglyphus daganensis, in northern Benin. The experiments were designed to expand on previous evaluation studies and contribute to a better understanding of the overall impacts of mycoinsecticide applications. The first experiment showed that acquisition of spores from the spray residue had a significant effect on mortality rate and a greater single influence on mortality than direct contact with spores from the spray aerosol. The second and third experiments revealed the mycoinsecticide to have sub‐ and pre‐lethal effects, causing a significant reduction in per capita feeding rate and increasing susceptibility to predation. The significance of these results for the overall impact of spray applications and for development of comprehensive evaluation methods are discussed.

Surveys of egg pods of agriculturally important grasshoppers were carried out in northern Benin between 1992 and 1995. Searches were made of oviposition sites under shrubs of the perennial legume Piliostigma thonningi along field margins. In 1993 and 1995, surveys were extended to include sorghum, Sorghum bicolor, and the perennial thatch grass Vetiveria nigritana. The four principal grasshopper species found at these oviposition sites were Hieroglyphus daganensis Krauss, Cataloipus fuscocoeruleipes Sjostedt, Kraussaria angulifera (Krauss) and Tylotropidius gracilipes Brancsik comprising 86% of 4545 identified egg pods while 651 egg pods could not be identified to species level. Predation by meloid beetles (Epicauta, Mylabris and Psalydolytta spp.) varied between 0 and 50% for the four dominant grasshopper species. From 1993 and 1994 data, nymphal eclosion from egg pods damaged by meloids was significantly lower than emergence from undamaged egg pods. The hymenopterous parasitoids Scelio africanus Risbec and S. mauriticanus Risbec were reared from the four dominant grasshopper species and parasitism levels of 0.0-3.3% were recorded from these hosts. There were significant differences in nymphaJ emergences between parasitized and unparasitized egg pods of H. daganensis.

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