Effect of <I>Bacillus thuringiensis</I> Transgenic Corn for Lepidopteran Control on Nontarget Arthropods

Abstract

Field populations of nontarget arthropods in transgenic corn with the MON 810 event expressing the Cry1Ab endotoxin from Bacillus thuringiensis variety kurstaki (Bt) were compared with those in conventional, near isogenic corn. The study was conducted at two locations in Georgia in 2001 and 2002 using visual counts, pitfall traps, and corn ear insect evaluations. Results were analyzed by trial using a repeated-measure analysis of variance (ANOVA) and a combined ANOVA of all trials. The only insect whose numbers were strongly affected by the Bt corn was the corn earworm, Helicoverpa zea (Boddie), a target insect. When averaged over all trials, larvae and adults of sap beetles, Carpophilus spp. (mostly C. lugubris Murray), and larvae of the otitid fly Euxesta stigmatis Loew were less abundant on Bt than non-Bt corn ears. Kernel damage caused by H. zea was less in Bt corn, which presumably made Bt corn ears less attractive to these insects. There were no consistent significant differences in nontarget phytophagous and predaceous arthropods in the visual counts and pitfall traps between Bt and non-Bt corn. One exception was Nabis spp., which was less abundant in Bt than non-Bt corn in the combined analysis. Flea beetles, mostly corn flea beetle, Chaetocnema pulicaria Melsheimer, were more abundant on Bt than non-Bt corn in the combined analysis but presumably were not adversely affected by the Bt corn. With the exception of nabids, these results indicate that transgenic Bt field corn containing the MON 810 event did not have an adverse effect on populations of nontarget phytophagous or predaceous arthropods in the Georgia corn system.