Baseline susceptibility of the fall armyworm (Lepidoptera: Noctuidae) to Cry1Ab toxin: 1998-2000

Abstract

'Attribute' sweet corn containing a cry1Ab 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 Cry1Ab 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 Cry1Ab 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 Cry1Ab 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 Cry1Ab protein produced in insect-resistant transgenic corn.