Corn School: Learnings from a 10-year fight with western bean cutworm


It’s been 10 years since the presence of western bean cutworm (WBC) was confirmed in Ontario.

Since then, the yield-robbing pest has moved beyond provincial hotspots such as Bothwell, Thamesville, and the sandy soils of Tillsonburg, and it continues to march eastward through to Quebec and into the Maritime provinces.

Ontario Ministry of Agriculture, Food and Rural Affairs entomologist Tracey Baute has been fighting to keep the pest at bay for the past decade. In this episode of RealAgriculture’s Corn School, she discusses the important role that the growing WBC Trap Network has played in learning how to manage WBC. Through the network, information is shared from growers and researchers on both sides of the border in the Great Lakes region to help fend off the pest.

The greatest impact of WBC is injury leading to increased mycotoxin development in grain. Photo: OMAFRA

“We’ve learned a lot and we keep learning,” says Baute who notes that the biggest challenge is the quality issues WBC creates when the larvae munches on ears and gives mycotoxins an opportunity to do even further damage.  Yield loss due to infestation of one WBC larva per ear has been estimated to reach 15 bu/ac. In Ontario, however, the risk of WBC injury leading to increased mycotoxin development in grain is of greater importance, notes Baute.

With more than 650 pheromone traps set up in the Great Lakes region, the network has been able to track the insect’s progress and gain valuable management insights, including when to scout and look for eggs, and ideal spray timing. Baute adds that management recommendations continue to evolve, including thresholds, which now recommend spraying when five percent of plants accumulate egg masses or small larvae over a two- to three-week period.

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Moving forward, Baute says the industry and growers will have to remain diligent in their WBC control efforts. The pest has developed resistance to Cry1F hybrids, which leaves Vip3A Bt hybrids and insecticides as the only means to protect against the insect.

“There’s not many other technologies coming down the pipeline for this pest so we really have to focus on resistance management,” says Baute. “There are a lot of acres that use one primary insecticide and that is just going to push this insect to resistance so we really have to focus on rotation for our management.”

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