Field evaluation of the impact of corn rootworm (Coleoptera: Chrysomelidae)-protected Bt corn on foliage-dwelling arthropods

A 3-yr field study was conducted in Monmouth, IL, to evaluate the effect of transgenic Bt corn expressing a Cry3Bb1 protein (MON 863) on foliage-dwelling arthropods. The study employed a split-plot design with MON 863 corn and a conventional non-Bt near isoline (RX670) as the main plots and insecticide regimens (no insecticide, imidacloprid applied as seed treatment, tefluthrin applied as soil treatment, and permethrin applied as foliar treatment) as subplots. Foliage-dwelling arthropods were sampled with sticky traps during each of the 3 yr (2000-2002). The most abundant taxa collected included corn pests, such as Diabrotica virgifera virgifera LeConte and Chaetocnema pulicaria Melsheimer (Coleoptera:Chrysomelidae), and Rhopalosiphum maidis Fitch (Homoptera:Aphididae). The most abundant generalist predators captured by sticky traps were Coccinellidae (ladybird beetles), Nabidae (damsel bugs), Orius insidiosus Say (minute pirate bugs), Syrphidae (flower flies), Chrysoperla carnea Stephens (green lacewings), Macrocentrus cingulum Rienhardt (a braconid parasitoid), and Araneae (spiders). MON 863 corn had no consistent adverse impact on the relative abundance of any nontarget foliage-dwelling arthropod taxon, including predators and parasitoids. However, insecticide applications of foliar insecticide (permethrin) significantly and consistently decreased the abundance of ladybird beetles, green lacewings, and damsel bugs compared with the insecticidal seed treatment or no insecticide application. The abundance of the pest R. maidis also was observed to increase in the foliar-applied insecticide treatment. Therefore, adoption of MON 863 and the concurrent reduction in broad-spectrum foliar-applied insecticide use for control of adult Diabrotica spp. have the potential to enhance biological control within corn agro-ecosystems.