The European corn borer, once a major pest for Midwest farmers, continues to pose a potential threat despite the widespread adoption of Bt corn since 1996, according to entomologists from Purdue University, Iowa State University and the University of Illinois on May 29.
Christian Krupke from Purdue University said, “There’s always a reservoir. They can still feed on non-Bt corn and non-GM acres. They also survive on alternate hosts like giant ragweed.” Erin Hodgson from Iowa State said, “Recent developments make it a timely topic, and one that I’ve been trying to raise awareness on. People who haven’t been farming 30 years don’t realize the potential devastation.”
Historically, European corn borer infestations could cost growers up to 60 or 70 bushels per acre under favorable conditions for the pest. Krupke described management as labor-intensive: “It required a tremendous amount of time. You were looking for very small egg masses that were easy to miss. Even if you found them, your control window was narrow because larvae soon tunneled into the plant.”
Nick Seiter from the University of Illinois explained how Bt corn transformed pest management: “Traits for ECB were incredibly effective and have been unbelievably successful for such an extended period of time,” he said. Hodgson added that high protein expression in Bt hybrids leads to nearly complete mortality among pests and fits well with ECB biology.
However, recent reports have identified in-field resistance to Bt traits by ECB populations in parts of the East Coast and Canada where single-trait use was common over several seasons. Seiter said, “These are not intense corn production areas. All of these corn-producing areas have been somewhat isolated, surrounded by millions of acres that are not in corn.” He continued, “Resistance alleles exist at a high enough rate to cause a problem in real field situations… Growers do not need to change their management behavior today, but if people see this, I don’t want them to brush it aside.”
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