EFFECTS OF BACILLUS-THURINGIENSIS TOXIN EXTRACTS ON FEEDING-BEHAVIOR AND DEVELOPMENT OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) LARVAE

Protein extracts of Escherichia coli expressing the toxin gene from Bacillus thuringiensis Berliner were tested for effect on the behavior and development of Leptinotarsa decemlineata Say using in vitro bioassays. Potato leaf disks coated with protein extracts were used as a diet. Toxicant properties and sublethal effects were scored with no-choice tests, and the relationship between dose of protein extract and larval growth and mortality was defined using regression analysis. Feeding behavior of young larvae was studied with choice tests. No antifeedant effects of B. thuringiensis toxins were found, even at concentrations that caused mortality or severely inhibited larval growth. The lack of feeding inhibition may limit strategies for producing transgenic potato plants with a low selection pressure against the target insect in the field.