| Abstract: | Laboratory and so-called extended laboratory bioassays were conducted in Benin, West Africa, to investigate the pathogenicity and virulence of the entomopathogenic fungus Metarhizium anisopliae var. acridum , a biocontrol agent against locusts and grasshoppers, to two hymenopteran parasitoids, Apoanagyrus ( = Epidinocarsis ) lopezi and Phanerotoma sp. Treatments were carried out under simulated field conditions at standard field dose rates of 2.5 and 5.0 ×10 12 conidia ha -1 . Test organisms were continuously (3 weeks) exposed to spray residues in artificial or simulated natural environments. The standard strain IMI 330 189 of the mycopesticide Green Muscle caused a significant reduction of 24% in the longevity ( = average survival time, AST) of A. lopezi , relative to the untreated control. Mycosis was confirmed in 16% of all cadavers. AST was shorter under low relative humidity (RH) conditions, and these conditions seemed to enhance susceptibility to fungal infection. However, this effect was only marginally significant. In contrast, average longevity of untreated A. lopezi was slightly yet significantly shorter at low RH (50-60%) than at high RH (80-90%). In the extended laboratory assay, the same isolate had no significant effect on mortality, parasitoid emergence ( = beneficial capacity) and sex ratio. In a further screening test with isolates IIBC I91 609, IIBC I93 833 and IMI 330 189 (reference), no infection of A. lopezi was confirmed. Similarly, Phanerotoma sp. was not susceptible to IMI 330 189. It is concluded that mycopesticides based on the three strains tested pose a low risk to parasitic hymenopterans under field conditions. |
