PATHOGENICITY OF THE ENTOMOGENOUS FUNGI METARHIZIUM-ANISOPLIAE AND BEAUVERIA-BASSIANA AGAINST CRUCIFER PESTS AND THE HONEY-BEE

The susceptibility of the cabbage stem flea beetle (Psylliodes chrysocephala; Coleoptera: Chrysomelidae) to different isolates of the entomogenous, hyphomycete fungi Beauveria bassiana and Metarhizium anisopliae, all from heterologous hosts, was investigated. The most pathogenic isolates were of M. anisopliae (V208, V233, V234, V242, V245, and V248). Studies were conducted to determine the virulence of V208 and V245, and their specificity for three other crucifer pests, Phaedon cochleariae, Myzus persicae and Lipaphis erysimi and a beneficial insect, Apis mellifera. Flea beetle mortality rates increased with dose; the estimated LC50s of V208 and V245 at 14 days post-inoculation were c. 10(6) conidia ml-1. The respective estimated LT50 values of V208 and V245 for P. chrysocephala at 1 x 10(7) conidia ml-1 were 10.0 and 9.3 days, and at 1 x 10(10) conidia ml LT50s were 3.8 and 4.2 days. Both V208 and V245 were pathogenic for P. cochleariae, M. persicae and L. erysimi. Myzus persicae and L. erysimi died within 4 days of inoculation. Bees were less susceptible to infection at low doses, but at 1 x 10(10) conidia ml-1 almost all bees had died by day 5 when the estimated LT50s for V208 and V245 were 4.4 and 8.5 days respectively.