Effects of cultivation of genetically modified Bt maize on epigeic arthropods (Araneae; Carabidae)

A field study was conducted in Germany to determine the possible effects of transgenic maize cultivation on nontarget epigeic predator organisms. During the growing period of 2001-2003, the activity abundances of spiders and carabid beetles were recorded and compared in three treatments: (1) Bt-maize (Mon 810) expressing the Cry1ab protein from Bacillus thuringiensis (Berliner), (2) an isogenic variety, and (3) the isogenic variety treated with insecticide. All three treatments were replicated in eight plots. The results were evaluated using three different methods. The activity abundances of single species were statistically analyzed by confidence interval methods. In addition, the phenological behaviors of the spider and carabid beetle species were determined, and multivariate statistical evaluation of the community by principal component analysis was conducted. Significantly different activity abundances in Bt plots compared with isogenic control plots were observed both for spiders and carabid beetles during 2001. However, in 2002 and 2003, no changes in community structure were detectable in any of the treatments. The change in the first year may have been caused by the influence of a massive cornborer infestation and accompanying large changes in microclimatic factors.