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Effect of seed blends and soil-insecticide on western and northern corn rootworm emergence from mCry3A + eCry3.1Ab Bt maize

Daniel L. Frank, Ryan Kurtz, Nicholas A. Tinsley, Aaron J. Gassmann, Lance J. Meinke, Daniel Moellenbeck, Michael E. Gray, Larry W. Bledsoe, Christian H. Krupke, Ronald E. Estes, Patrick Weber, Bruce E. Hibbard
Journal of economic entomology 2015 v.108 no.3 pp. 1260-1270
Bacillus thuringiensis, Diabrotica barberi, Diabrotica virgifera virgifera, corn, eclosion, proteins, resistance management, rootworms, seed mixtures, seed treatment, soil, survival rate, tefluthrin, transgenic plants, Midwestern United States
Blended seed mixtures containing various ratios of transgenic Bt maize expressing the mCry3A + eCry3.1Ab proteins and non-Bt maize (near-isoline maize) were deployed alone and in combination with a soil applied insecticide (Force CS) to evaluate the survivorship of the western corn rootworm, Diabrotica virgifera virgifera LeConte, in a total of nine field environments across the Midwestern United States in 2010 and 2011. Northern corn rootworm, Diabrotica barberi Smith & Lawrence emergence was also evaluated in four of these environments. Both western and northern corn rootworm beetle emergence from all Bt treatments was significantly reduced when compared with beetle emergence from near-isoline treatments. When evaluating western corn rootworm beetle emergence from various ratios of mCry3A + eCry3.1Ab:near-isoline, 2.6, 4.2, and 6.7 fold more beetles emerged from 95:5, 90:10, and 80:20 blended seed treatments, respectively than from the 100:0 treatment when data from all environments were averaged together. Similar data from the northern corn rootworm resulted in 2.8, 3.2, and 4.2 fold more beetles than from the 100:0 treatment. The addition of Force CS (tefluthrin) significantly reduced western corn rootworm beetle emergence for each of the three treatments to which it was applied. Force CS also significantly delayed the number of days to 50% beetle emergence in western corn rootworms. Time to 50% beetle emergence in the 100% mCry3A + eCry3.1Ab treatment with Force CS was delayed 13.7 d when compared with western corn rootworm beetle emergence on near-isoline corn. These data are discussed in terms of rootworm resistance management.