Interactive Effects of an Antifeedant Used with Bacillus thuringiensis var. san diego Delta Endotoxin on Colorado Potato Beetle (Coleoptera: Chrysomelidae

The effects of citrus limonoid antifeedants used alone and in sequence with a Bacillus thuringiensis var. san diego delta endotoxin product against the Colorado potato beetle, Leptinotarsa decemlineata (Say), were examined in laboratory and field tests. In the laboratory, prior exposure to citrus limonoid did not alter Colorado potato beetle mortality in response to the endotoxin. Larval development time was significantly slower among larvae treated with limonoid or endotoxin; the most delayed development occurred among larvae receiving endotoxin following limonoid treatment. In field tests, rates of Colorado potato beetle adult colonization and oviposition were significantly lower in plots treated with endotoxin following treatment with limonoid compared with plots treated with either compound alone. Bioassays and chemical analyses of residues indicate that limonoids persist on potato foliage for ≈6-8 d under field conditions. The tests indicate that citrus limonoid antifeedants may be effectively used in conjunction with B. thuringiensis var. san diego endotoxin in an integrated approach to Colorado potato beetle management.