Assessing the Risk to Nontarget Organisms from Bt Corn Resistant to Corn Rootworms (Coleoptera: Chrysomelidae): Tier-I Testing with Orius insidiosus (Heteroptera: Anthocoridae)

A 14-d continuous dietary exposure bioassay using nymphs of the insidious flower bug, Orius insidiosus (Say) (Heteroptera: Anthocoridae), was conducted to assess nontarget impacts of genetically modified corn event MON 863 expressing the Cry3Bb1 protein for management of corn rootworms, Diabrotica spp. (Coleoptera: Chrysomelidae). Nymphs of O. insidiosus were continuously fed a bee pollen diet inoculated with a maximum hazard exposure dose (930 microg/g of diet) of the Cry3Bb1 protein for 14 d. The Cry3Bb1 protein at a concentration of 930 microg/g of diet had no adverse effect on the survival and development (to adults) of O. insidiosus nymphs. In contrast, when O. insidiosus nymphs were fed bee pollen diet treated with a hazard dose of the protease inhibitor E64 (53 microg/g of diet) or the stomach poison potassium arsenate (8.9 microg/g of diet), all nymphs died before developing to adults. Furthermore, statistical power analysis indicated that at levels of 80% power and a 5% type I error rate, the study design would have been able to detect a minimum 30% reduction in survival of test nymphs and a 20% reduction in nymphal development to the adults relative to the buffer control groups. Based on the maximum level (93 microg/g) of the Cry3Bb1 protein expressed in MON 863 corn tissues including leaves, roots, and pollen, findings from this study indicate that corn hybrids containing the MON 863 event have a minimum 10 times safety factor for nymphs of O. insidiosus and thus pose minimal risk to this beneficial insect.