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Effects of refuges on the evolution of resistance to transgenic corn by western corn rootworm, Diabrotica virgifera virgifera LeConte

Jennifer Deitloff, Mike W. Dunbar, David A. Ingber, Bruce E. Hibbard, Aaron J. Gassmann
Pest management science 2016 v.72 no.1 pp. 190-198
Bacillus thuringiensis, Diabrotica virgifera virgifera, Zea mays, bioassays, corn, crops, crystal proteins, delta-endotoxins, evolution, insect pests, integrated pest management, pesticide resistance, resistance management, transgenic plants
Diabrotica virgifera virgifera LeConte is a major pest of corn causing millions of dollars of economic loss annually through yield reductions and preventative management practices. Corn producing toxins derived from Bacillus thuringiensis (Bt) have been developed to help manage D. v. virgifera. Since Bt corn became commercially available for management of D. v. virgifera, studies have demonstrated the ability of this species to evolve resistance to Bt toxins in both laboratory and field settings. Two refuge strategies, a block refuge and a blended refuge, are employed to delay evolution of resistance to Bt crops by pest insects. We used an experimental evolution approach to compare the efficacy of the block and blended refuge strategies in delaying resistance in D. v. virgifera to the Bt toxin Cry34/35Ab1. In agreement with many other studies of D. v. virgifera, we confirm that this pest developed resistance after multiple generations on Bt corn. However, we also found evidence in some bioassays that refuges delayed the development of resistance. In general, we found that the block-refuge strategy delayed resistance evolution to a greater extent than the blended-refuge strategy. Because D. v. virgifera evolved resistance to Bt corn even when refuges were present, refuges alone are likely not enough to delay resistance in the field. Applying integrated pest management, which uses a variety of methods to manage pest populations, in addition to using insect resistance management is likely the best approach for managing D. v. virgifera populations and delaying the evolution of Bt resistance.