Laboratory Testing of Metarhizium spp. and Beauveria bassiana on Sahelian Non-target Arthropods

Abstract

Laboratory experiments were conducted to investigate the host specificity of 11 isolates of Metarhizium sp. and one isolate of Beauveria bassiana , all deuteromycete entomopathogenic fungi that are being tested as potential biocontrol agents against locusts and grasshoppers. Metarhizium sp. (isolate IMI 330 189) was applied topically to Pimelia senegalensis and Trachyderma hispida, two Sahelian tenebrionid beetles. No infection was observed at a dose of ca. 2.5 x 106 conidia per insect, much higher than dose rates likely to occur in the field. The hymenopteran parasitoids Bracon hebetor (Braconidae) and Apoanagyrus lopezi (Encyrtidae) were exposed to surfaces treated with the entomopathogens at a rate equivalent to ca. 5 x 1012 spores ha-1, the recommended field rate against locusts. All 12 isolates tested resulted in 100% mortality of the parasitoids. Average survival times ranged from 1.6 to 4.1 days. In all cases there was fungal outgrowth on the cadavers. Exposure time-response experiments further confirmed the pathogenicity of these fungi to the parasitoids. The possibility of these parasitoids being affected in the field is discussed.