LONDON, Ont. – Farmers weren’t too worried when the western bean cutworm showed up in Ontario in 2008.
Three years later, they’re beginning to become concerned.
“We feel the pest will cause economic damage this year, but just in a few locations,” said University of Guelph researcher Jocelyn Smith.
“It seems the heaviest infestations are on the sandier soils.”
The cutworm affects corn and edible bean crops.
Yield losses in corn in regions where the pest has been a problem have reached as high as 40 percent with several larvae feasting on each ear.
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“Unlike the corn borer, you can find more than one in an ear,” Smith said.
“They’re not cannibalistic. They don’t eat each other.”
Until the 1990s, the western bean cutworm was only a problem in the western U.S. corn belt, including Colorado and Nebraska.
However, it has moved gradually eastward, and its population has increased substantially since first being detected in Ontario in 2008.
Smith suspects the cutworms are now overwintering in the province.
She said the eastern migration may be caused by an increase in zero tillage or the increasing use of Bt corn.
There are control measures. Insect predators are already attacking the pest in Ontario and Smith feels Mother Nature may eventually help strike a balance.
Deep cultivation also helps.
Smith said there’s much to learn about the cutworms’ habits under Ontario conditions, but it appears they overwinter six to nine inches below the soil surface.
Another solution is Signet’s Agrisure Viptera, which provides good control in the same way that BT corn controls the European corn borer. It was approved for use in Canada in April.
BT Cry1F event (Herculex) for European corn borer provides 70 to 90 percent control.
Insecticides such as Matador and Decis can provide control but the timing of application needs to coincide with larvae emergence. A single spray may not be enough in heavily infested fields.
The cutworm is a native of North America. It lays its eggs in clusters of as many as 200 on the upper surface of a corn leaf close to the top of plant.
The tassel is targeted first, followed by the silk and finally the ears. The cutworms spend up to 60 days feeding, after which they drop to the ground and bury themselves.
They overwinter as larvae, encased in soil cells, and pupate around June. The adults emerge from late July to the middle of August.
