Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2005
Publication Date: 2/7/2006
Citation: Duan, J.J., Paradise, M.S., Lundgren, J.G., Bookout, J.T., Jian, C., Wiedenmann, R.N. 2006. Assessing non-target impacts of bt corn resistant to corn rootworms: tier-1 testing with larvae of Poecilus chalcites (coleoptera: carabidae). Environmental Entomology. 35(1):135-142.
Interpretive Summary: Transgenic crops should be compatible with other pest management tactics, including biological control, to improve their long-term sustainability. One important group of natural enemies in agriculture are ground beetles (Coleoptera: Carabidae), of which Poecilus chalcites is an abundant member. Here, we evaluated the effects of purified Cry3Bb1 protein, which is toxic to corn rootworm beetles, to various fitness parameters of P. chalcites larvae in the laboratory. Essentially, at 10x the level expressed in transgenic corn, we were unable to detect any deleterious effects on P. chalcites development. We conclude that this transgenic event poses minimal direct toxicity to this species of ground beetle.
Technical Abstract: A dietary exposure bioassay with larvae of the ground beetle, Poecilus chalcites (Say) (Coleoptera: Carabidae) was developed for the purpose of assessing potential non-target impacts of transgenic corn event MON 863 expressing the Cry3Bb1 protein for control of corn rootworms, Diabrotica sp (Coleoptera: Chrysomelidae). The assay involved 28 days of continuous exposure of larvae of P. chalcites to an artificial diet treated with a maximum hazard dose (930 ug/g of diet) of the Cry3Bb1 protein. Results from this study demonstrated that the Cry3Bb1 protein at a concentration of 930 ug/g of diet had no adverse effect on the survival, development, and growth (biomass) of the larvae of P. chalcites. Further, statistical power analysis of the experimental design indicated that with a desired level of 80% power and a 5% of type-I error rate, the design with 66 individual P. chalcites larvae per treatment would have been able to detect a minimum of 14% (at day 7) to 19% (at days 14, 21, and 28) reduction in survival of test larvae resulting from an adverse treatment (relative to the negative buffer control group). With the desired level of 80% power and 5% type-I error rate, the study design with 60 surviving insects per treatment would have been able to detect approximately a minimum 21% reduction or 27% increase in biomass measured at day 14 of the dietary exposure, and an 18% reduction or 22% increase in biomass at day 28. Based on the maximum level (93 ug/g) of the Cry3Bb1 protein expressed in MON 863 corn tissues including leaves, roots, and pollen, findings from this study suggest that corn hybrids containing the MON 863 event would have a minimum of 10X safety factor for larvae of P. chalcites, and thus poses little risk to this non-target beneficial insect.