Virulence of the Entomopathogenic Fungus Metarhizium flavoviride Gams and Rozsypal and Toxicity of Diflubenzuron, Fenitrothion-Esfenvalerate and Profenofos-Cypermethrin to Nontarget Arthropods in Mauritania

Abstract.

Within the framework of the GTZ project, Biological and Integrated Control of Locusts and Grasshoppers, a laboratory screening for Metarhizium flavoviride (strain Mfl 5) blastospore pathogenicity to the nontarget arthropods Pharoscymnus anchorago F. (Coleoptera: Coccinellidae), Trachyderma hispida (Forskål) (Coleoptera: Tenebrionidae), Palpares cf. tesselatus Rambur (Neuroptera: Myrmeleontidae) and Thanatus sp. (Araneae: Philodromidae) was conducted in Akjoujt research station, Mauritania. Various larval stages of desert locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae), were tested as positive controls. The insect growth regulator diflubenzuron was used as a reference in the bioassay with P. anchorago. In addition, two organophosphate-pyrethroid insecticides widely used in locust control, fenitrothion-esfenvalerate (P. anchorago, T. hispida) and profenofos-cypermethrin (Thanatus sp.) were tested as toxic standards. M. flavoviride was not pathogenic to nontargets, but very virulent to S. gregaria. The results provided further evidence that the host range of M. flavoviride (Mfl5), a strain isolated from migratory locust in Madagascar, is very narrow. Diflubenzuron was toxic to P. anchorago and to S. gregaria. The LD50s of both chemical insecticides tested were considerably lower than the expected initial environmental concentration. The beneficial P. anchorago, a natural enemy of scale insects in date palms, was considered most at risk in the course of chemical locust control. The use of mycopesticides to control desert locust in date palm plantations offers an environmentally safe and economically viable alternative to chemical control.