Corn School: Resistance driving European corn borer comeback

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European corn borer wreaked havoc for decades in cornfields across North America before the adoption of transgenic traits (Bt) in the late 1990s effectively punched out the pest.

Earlier this year at Southwest Crop Diagnostic Days at the University of Guelph’s Ridgetown campus, Ontario ministry of agriculture entomologist Tracey Baute noted that the yield-robbing insect had fallen so far off the radar that it hasn’t been a featured topic at the annual crop diagnostic event since 1997.

But corn borer (ECB) is making a comeback and was on the Diagnostic Days agenda this year thanks to growing resistance to the transgenic traits.

On this episode of the Real Agriculture Corn School, University of Guelph research scientist Jocelyn Smith tells host Bernard Tobin how ECB resistance was first found in Truro, Nova Scotia in 2018. Since that discovery, Smith notes that researchers have ramped up monitoring for resistance across Canada and have now found resistant populations near Montreal, Que., and Carmen, Man.

In the video, Smith shares how she toured Nova Scotia fields and found corn borers in 30 to 70 per cent of plants that carried the Cry1F protein, which had protected plants against the pest for two decades. (Story continues after the video.)

There are four proteins, including Cry1F, that growers rely on to fight the pest. With the increased monitoring, Smith says that researches are now starting to see problems with the other proteins.

What’s the potential for resistance to grow and spread? “The adult is a moth. They do overwinter in the corn stalks way down low on the corn plant, but in the spring they fly out of the field, and they look for grassy areas where the mating happens,” Smith notes. “And then they go lay their eggs in a different field, so it could spread and those moths can fly up to 40 kilometres in one generation — and in some years, we have two generations per year — so there’s potential there for this to spread, unfortunately, fairly quickly.”

How can growers, agronomists and the seed industry fend off the potential of growing resistance? Smith says developing a new protein will likely take eight to 10 years so technology will not provide an immediate defence.

In the meantime, the best options include: strong crop rotations; learning to identify and scout for the pest; stalk pulverizing and destruction in regions where hot spots emerge; and biological control. Insecticides are also an option, but not an effective choice, Smith adds.

Click here for more Corn School videos.

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Corn School (view all)Season 12 (2023) Episode 8
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