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Resistance to Bt corn by western corn rootworm (Coleoptera: Chrysomelidae) in the U.S. corn belt

Eileen M. Cullen, Michael E. Gray, Aaron J. Gassmann, Bruce E. Hibbard
Journal of integrated pest management 2013 v.4 no.3 pp. 1-6
insecticides, genetic traits, integrated pest management, insects, insecticidal proteins, growers, hybrids, Bacillus thuringiensis, planting, biological resistance, pesticide use reduction, germplasm, Ostrinia nubilalis, corn, resistance management, Diabrotica virgifera virgifera, business enterprises, transgenic plants, cropping systems, population, evolutionary adaptation, bacteria, United States, Corn Belt region
Transgenic Bt corn hybrids that produce insecticidal proteins from the bacterium Bacillus thuringiensis Berliner have become the standard insect management tactic across the United States Corn Belt. Widespread planting of Bt corn creates intense selection pressure for target insects to develop resistance, and evolution of resistance is the greatest threat to benefits associated with Bt corn such as reduced reliance on conventional insecticides. Recognizing the threat of resistance, the U.S. Environmental Protection Agency requires seed companies to include an insect resistance management (IRM) plan when applying to register a Bt trait. The goal of IRM plans is to delay Bt resistance in populations of target insects. One element of IRM is the presence of a non-Bt refuge to maintain Bt-susceptible individuals within a population, and growers are required to implement IRM on-farm by planting a refuge. Field-evolved resistance has not been detected for the European corn borer, Ostrinia nubilalis (Hubner), even though this species has been exposed to Bt proteins common in US corn hybrids since 1997. The IRM situation is unfolding differently for Bt corn rootworm protected corn and the western corn rootworm, Diabrotica virgifera virgifera LeConte. In this paper, we examine the scientific evidence for D. v. virgifera adaptation to Bt rootworm traits and cropping system practices that have contributed to the first reports of field-evolved resistance to a Bt toxin by D. v. virgifera. We explain why this issue has developed, and emphasize the necessity of an integrated pest management approach to address the issue.