Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2002
Publication Date: 7/1/2003
Citation: LYNCH, R. E., HAMM, J. M., MYERS, R. E., GUYER, D., STEIN, J. BASELINE SUSCEPTIBILITY OF THE FALL ARMYWORM (LEPIDOPTERA: NOCTUIDAE) TO CRY1AB TOXIN: 1988-2000. J. ENTOMOL. SCI. 38(3):377-385. 2003. Interpretive Summary: Sweet corn for both the fresh market and for processing is sprayed intensively with insecticides to prevent insect damage to the ears. The most important pests of sweet corn are the European corn borer, corn earworm and fall armyworm. Novartis Seeds, Inc. (Currently Syngenta Seeds, Inc.) developed transgenic sweet corn, `Attribute', that contained a gene from the bacterium Bacillus thuringiensis (Bt) that confers a high level of resistance to European corn borer and corn earworm, and a moderately high level of resistance to the fall armyworm. However, one of the main concerns is that insects will develop resistance to the Bt gene and it will no longer be effective in controlling these insects. The EPA developed a resistance management program as part of the approval for commercialization of Attribute sweet corn which required annual monitoring of these insects for resistance to the toxin produced by the Bt gene. We monitored susceptibility of fall armyworm collected from Belle Glade, FL, Homestead, FL, Weslaco, TX, and Corpus Christi, TX in 1998, 1999, and 2000. Based on mortality data when larvae were fed the Bt toxin, fall armyworms from these locations were not developing resistance to the Bt toxin found in Attribute sweet corn.
Technical Abstract: `Attribute' sweet corn containing a Cry1Ab gene (Bt11Event) from Bacillus thuringiensis 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 over 10 years 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.