Season-long abundance of generalist predators in transgenic versus nontransgenic potato fields

We estimated the effect of deploying Cry3A-transgenic potatoes resistant to the Colorado potato beetle, Leptinotarsa decemlineata (Say), on the season -long relative abundance of naturally-occurring generalist predators. Low i nputs of foliar insecticides were used in the transgenic fields to suppress nontarget pests and in the nontransgenic fields to prevent total defoliati on of potato plants by L. decemlineata. Dominant plant-foraging heteroptera n predators and lady beetles were sampled by sweeping foliage, whereas, gro und-foraging carnivorous carabids, ants, and spiders were sampled by trappi ng in pitfalls. Orius insidiosus (Say) was significantly (P less than or eq ual to 0.05) more abundant in transgenic treatment fields than in nontransg enic fields in 1994, but not in 1995. None of the coccinellids (3 taxa) wer e affected by the treatments in either season. The carnivorous carabids (3 taxa) and ants were not affected by either treatment, but spiders were sign ificantly more abundant in the transgenic treatment fields in 1995. We conc lude that the deployment of pure stands of Cry3A-transgenic potatoes, with a minimum input of insecticides to suppress non-target pests, will have no deleterious effects on the populations of generalist predators in the potat o ecosystem.