Tuesday, August 30, 2011

Resistance by Corn Rootworm to Bt Corn Reported in Parts of Iowa

Recently, Dr. Aaron Glassman* and colleagues have reported field resistance to Bt corn by western corn rootworm in portions of Iowa. Though this problem has been anticipated by many, this is the first scientifically documented & published occurrence of field-evolved resistance to a Bt toxin by the corn rootworm and any species of beetle.

Prevention, and failing that, management of pest resistance is one of the major benefits of using IPM techniques in your insect management program. In KY we have all three major species of corn rootworm including the western. In KY field corn production these pests are extremely well controlled by our extensive use of crop rotation. Because of this high level of essentially “free” corn rootworm control, and the possibility of developing resistance when the population is exposed to the Bt toxin, we recommend NOT planting a corn product that contains the rootworm Bt events except in very specific circumstances.

To read a summary of this report go to Kentucky Pest News and see the article written by Ric Bessin and Doug Johnson at:


To read the original scientific paper, go to:


-OR- go to: http://www.plosone.org/home.action and type 222629 into the "search articles…" box.

*Grassmann, A.J., J.L. Petzold-Maxwell, R.S. Keweshan, M.W. Dunbar. 2011. Field-Evolved Resistance to Bt Maize by Western Corn Rootworm. PLoS ONE 6(7): e22629.

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