Susceptibility of the Convergent Lady Beetle (Coleoptera: Coccinellidae) to Four Entomogenous Fungi

Abstract

Many entomogenous fungi used as biological control agents of insect pests have broad host ranges and may infect nontarget organisms, potentially causing unanticipated environmental effects. We tested the susceptibility of a predatory beetle, Hippodamia convergens Gueerin-Meneville, to five entomogenous fungi, all of which are being considered or used for pest control; Metarhizium anisopliae, Paecilomyces fumosoroseus, Nomuraea rileyi , and two strains of Beauveria bassiana. First-instar beetle larvae were exposed in laboratory bioassays to five concentrations of fungal preparations ranging from 104 to 108 conidia/ml. M. anisopliae caused up to 97% mortality, an aphid-derived strain of B. bassiana caused up to 95% mortality, a beetle-derived strain of B. bassiana caused up to 75% mortality, and P. fumosoroseus caused up to 56% mortality. The rate of mortality was dependent on exposure concentration. No infection was detected with N. rileyi. We conclude that M. anisopliae , B. bassiana , and P. fumosoroseus have the potential to infect H. convergens if used in crops where this predator occurs, whereas N. rileyi does not. The original host species of the fungi did not indicate their degree of virulence toward the beetle, probably because most of the fungi tested have very broad host ranges in general.