Corn rootworm is the number one pest that corn growers have to manage every single year. For years, one of the top rootworm management tools has been Bt corn. However, due to widespread usage, the effectiveness of Bt corn has decreased over time. Something needs to be done now to ensure that Bt corn remains as an effective tool in the farmer’s toolbox. Aaron Gassmann, professor of plant pathology at Iowa State University, said his lab has been studying this for well over a decade.
Gassmann recently co-authored the study “Too much of a good thing: lessons from compromised rootworm Bt maize in the US Corn Belt,” which dove into how overplanting Bt corn causes farmers to lose some of its benefits for suppressing rootworm and protecting yields. Gassmann said they found that some farmers were using Bt corn higher than the ideal rate, which promoted resistance.
In a separate study, Gassmann said that the way that Bt corn genetics are packaged together can also be harmful to the effectiveness of those traits.
Fortunately, Gassmann said there are other things that farmers can do to prevent corn rootworm from becoming resistant to Bt traits.
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