The 'Billion-Dollar Pest' Reappears in Canada, Connecticut

European corn borers once wreaked havoc on corn until the introduction of Bt corn. Is the pest making a reappearance?

- By Sophie Winkelpleck

In 2018, farmers in Nova Scotia, Canada, noticed a pest they hadn’t seen in a long time — the European corn borer. The pest was introduced to the United States in 1917 and spread to most major corn-growing regions by the 1940s.

Coined “the billion-dollar pest,” the European corn borer caused yield loss by burrowing into cornstalks and feeding on them until the introduction of Bt corn in 1996. The main indicator of the borer is a horizontal line of shot holes in the corn leaves.

The discovery in Nova Scotia led researchers to investigate throughout Canada, where they continued to find the same Cry1F resistance in the borer as they found in Nova Scotia. Cry1F is the crystalline protein used in Bt corn that keeps larvae at bay.

“In the years from 2018-2023, researchers started to make collections all across Canada, and they were finding European corn borer resistance to Cry1F toxins all across the board,” said Kelsey Fisher, agricultural entomologist for the Connecticut Agricultural Experiment Station.

The Experiment

Because of the Cry1F resistance discoveries in Canada, Fisher said she wanted to see if resistance were occurring in the United States. Fisher, who holds a PhD in entomology, said Nova Scotia was “late to the party” of using double-toxin products and was still using a single-toxin product, something that has been taken off the market in the Midwest. In 2023, she began by planting five different varieties of sweet corn in a 15-acre field at Lockwood Farms in Hamden, just north of the agricultural experiment station’s location in New Haven.

“There is no Cry1F in sweet corn, so we couldn’t test for Cry1F resistance,” Fisher said. “We also didn’t think I was going to find anything.”