Baseline Susceptibility of the Fall Armyworm (Lepidoptera: Noctuidae) to CrylAb Toxin: 1998–2000

‘Attribute’ sweet corn containing a crylAb gene (Bt11 Event) from Bacillus thuringiensis Berliner was registered for commercial use in 1998. A requirement of registration was to conduct baseline susceptibility studies to CrylAb toxin in fall armyworm populations collected from sweet corn growing areas in south Texas and south Florida. In addition, fall armyworm populations collected in sweet corn growing areas must be annually monitored for changes in susceptibility to the CrylAb protein. Fall armyworm larvae were collected near Belle Glade, FL, Homestead, FL, Weslaco, TX, and Corpus Christi, TX, in 1998 through 2000 and evaluated for susceptibility to CrylAb toxin. The Tifton Laboratory colony of fall armyworm that has been in culture for more than 10 yrs was used as the susceptible control. Comparison of the calculated LC₅₀S for the various colonies did not indicate an appreciable change in susceptibility during the period 1998–2000. These data provide baseline information as to the susceptibility of the fall armyworm to CrylAb protein produced in insect-resistant transgenic corn.