Evidence of Resistance to Cry34/35Ab1 Corn by Western Corn Rootworm (Coleoptera: Chrysomelidae): Root Injury in the Field and Larval Survival in Plant-Based Bioassays

Authors

Aaron J. Gassmann, Iowa State UniversityFollow
Ram B. Shrestha, Iowa State UniversityFollow
Siva R. K. Jakka, Iowa State UniversityFollow
Mike W. Dunbar, Iowa State UniversityFollow
Eric H. Clifton, Iowa State UniversityFollow
Aubrey R. Paolino, Iowa State UniversityFollow
David A. Ingber, Department of Entomology, Iowa State UniversityFollow
B. Wade French, Northern Grain Insects Research Laboratory, USDA-ARSFollow
Kenneth E. Masloski, Iowa State UniversityFollow
John W. Dounda, Iowa State UniversityFollow
Coy R. St. Clair, Iowa State UniversityFollow

Document Type

Article

Date of this Version

2016

Citation

Journal of Economic Entomology, 2016, 1–9 doi: 10.1093/jee/tow110

Comments

Copyright The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved.

Abstract

Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a serious pest of corn in the United States, and recent management of western corn rootworm has included planting of Bt corn. Beginning in 2009, western corn rootworm populations with resistance to Cry3Bb1 corn and mCry3A corn were found in Iowa and elsewhere. To date, western corn rootworm populations have remained susceptible to corn producing Bt toxin Cry34/35Ab1. In this study, we used single-plant bioassays to test field populations of western corn rootworm for resistance to Cry34/35Ab1 corn, Cry3Bb1 corn, and mCry3A corn. Bioassays included nine rootworm populations collected from fields where severe injury to Bt corn had been observed and six control populations that had never been exposed to Bt corn. We found incomplete resistance to Cry34/35Ab1 corn among field populations collected from fields where severe injury to corn producing Cry34/35Ab1, either singly or as a pyramid, had been observed. Additionally, resistance to Cry3Bb1 corn and mCry3A corn was found among the majority of populations tested. These first cases of resistance to Cry34/35Ab1 corn, and the presence of resistance to multiple Bt toxins by western corn rootworm, highlight the potential vulnerability of Bt corn to the evolution of resistance by western corn rootworm. The use of more diversified management practices, in addition to insect resistance management, likely will be essential to sustain the viability of Bt corn for management of western corn rootworm.