|French, Bryan - Wade|
Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/12/2005
Publication Date: 12/1/2005
Citation: Mcmanus, B.L., Fuller, B.W., Boetel, M.A., French, B.W., Ellsbury, M.M., Head, G.P. 2005. Abundance of lady beetles (Coleoptera: Coccinellidae) in corn rootworm-resistant Cry3Bb1 maize. Journal of Economic Entomology. 98:1992-1998. Interpretive Summary: Concern over possible side-effects on beneficial insects from the introduction of genetically-modified corn with resistance to corn rootworms motivated this research. Findings from this study indicate that genetically-modified corn does not lead to lower numbers of adults of a common lady beetle, Coleomegilla maculate. Hybrid corn with implanted genes for corn rootworm resistance could, in fact, help conserve beneficial insects, such as lady beetles, by allowing farmers to decrease their reliance on soil insecticides currently used for managing corn rootworm larvae in maize. As a result, increased predator abundance in maize is more likely to provide some natural control of insect pest.
Technical Abstract: Lady beetles (Coleoptera: Coccinellidae) are important polyphagous predators of insect pests in maize fields. Transgenic Cry3Bb1 maize hybrids express a coleopteran-specific insecticidal protein derived from the kumamotoensis subspecies of Bacillus thuringiensis (Berliner) that was bioengineered to induce corn rootworm larval mortality. This study evaluated the impact of Cry3Bb1-based hybrid (corn rootworm-resistant maize) on coccinellid abundance in relation to preanthesis, anthesis, and postanthesis maize-developmental periods near Brookings, South Dakota during 2001 and 2002. Pherocon AM Sticky trap data did not reveal deleterious impacts on coccinellid adult abundance in maize, irrespective of development period. Numbers of adult coccinellids captured in Cry3Bb1 maize were not significantly different from those in untreated plots during preanthesis, and adults were actually more abundant in Cry3Bb1 maize than in tefluthrin-treated and untreated plots during anthesis and postanthesis. Similar results were found for the dominant coccinellid species Coleomegilla maculata DeGeer that represented 73.5 and 69.9% of all adult lady beetles captured in 2001 and 2002, respectively. Whole-plant sampling also indicated an overall lack of negative effects by the transgenic maize on abundance of egg, larva, pupa, and adult lady beetles. The overall findings of this investigation clearly indicate that Cry3Bb1-expressing hybrids are not likely to impose harmful effects on coccinellids common to maize production systems. Our research further suggests that Cry3Bb1 maize has the potential for conservation of lady beetle complexes in maize production areas.