Susceptibility of Field Populations of the Cotton Bollworm in the Southern U.S. to Four Individual Bt Proteins

The cotton bollworm, Helicoverpa zea (Boddie), is one of the most important insect pests of cotton, Gossypium hirsutum L. Transgenic cotton plants expressing one or more Bacillus thuringiensis (Bt) proteins have been widely planted for control of cotton bollworms since 1996. However, extensive and constant exposure of cotton bollworms to Bt proteins may result in a shift towards a reduction in susceptibility. To estimate the susceptibility of the field populations of cotton bollworm to Bt proteins, we compared the survivorship of F1 or F2 generations of field-derived cotton bollworms collected from Mid-South region in the U.S. to four individual Bt proteins (Cry1Ac, Cry1F, Cry2Ab2, and Vip3a) with that of a susceptible counterpart using diet overlay bioassays. Results generated from this study would provide essential information for Bt resistance management in the Southern U.S.