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

Authors: DIETLOFF, JENNIFER - University Of Iowa; DUNBAR, MIKE - University Of Iowa; INGBER, DAVID - University Of Iowa; Hibbard, Bruce; GASSMANN, AARON - University Of Iowa

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2015
Publication Date: 2/27/2015
Publication URL: http://handle.nal.usda.gov/10113/61784
Citation: Dietloff, J., Dunbar, M.W., Ingber, D.A., Hibbard, B.E., Gassmann, A.J. 2015. Effects of refuges on the evolution of resistance to transgenic corn by western corn rootworm, Diabrotica virgifera virgifera LeConte. Pest Management Science. 72:190-198.

Interpretive Summary: The western corn rootworm 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 western corn rootworm. Since Bt corn became commercially available for management of western corn rootworm, 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 western corn rootworm to a specific Bt toxin (Cry34/35Ab1). In agreement with many other studies involving this pest, 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 western corn rootworm 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 western corn rootworm populations and delaying the evolution of Bt resistance.

Technical Abstract: 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.