GEOGRAPHIC SUSCEPTIBILITY OF HELIOTHIS-VIRESCENS AND HELICOVERPA-ZEA (LEPIDOPTERA, NOCTUIDAE) TO BACILLUS-THURINGIENSIS

Geographic variability in sensitivity of field-collected Heliothis virescens (F.) and Helicoverpa zea (Boddie) to Bacillus thuringiensis (Berliner) was studied to establish a geographic baseline for comparison of future population responses to the increased use of B. thuringiensis-based insect control products. Colonies of H. virescens and H. zea were established from populations collected from several southern states, plus Hawaii and the Virgin Islands. Populations were evaluated for their susceptibility to a microbial B. thuringiensis product, Dipel, and to purified CryIA(c) endotoxin protein. The range of LC50s among populations in response to Dipel and purified endotoxin, respectively, were 3.6- and 8-fold for H. virescens and 13- and 16-fold for H. zea.