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), w ere examined in laboratory and field tests. In the laboratory, prior e xposure to citrus limonoid did not alter Colorado potato beetle mortal ity in response to the endotoxin. Larval development time was signific antly slower among larvae treated with limonoid or endotoxin; the most delayed development occurred among larvae receiving endotoxin followi ng 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 anal yses of residues indicate that limonoids persist on potato foliage for almost-equal-to 6-8 d under field conditions. The tests indicate that citrus limonoid antifeedants may be effectively used in conjunction w ith B. thuringiensis var. san diego endotoxin in an integrated approac h to Colorado potato beetle management.