Continuous canola can lead to root maggot damage

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If your rotation is canola, snow, and canola again, you’re setting yourself up for a root maggot infestation.

Insects love it when you grow the same crop year after year, and root maggots and canola are no exception, University of Alberta entomologist Lloyd Dosdall told attendees at a recent Alberta Canola industry update seminar.

Dosdall was part of a research team that examined how canola rotation — or the lack of it — affects crop damage, yield and seed quality. The study examined 13 different treatments done across Western Canada at five different sites from 2008 to 2011.

Several sites were continuously cropped with canola, while others had a canola-wheat-canola rotation or only had canola in one of the three years. At the end of the season, researchers examined root damage to determine the severity of root maggot infestation.

“The damage to canola that was grown continuously was more severe than when canola was rotated,” said Dosdall.

Root maggot larvae overwinter in soil and the study found the damage they cause increased every year.

“We had the highest yields in the first year of continuous canola, and then they just dropped down significantly in the following two years,” he said.

Dosdall said the loss from continuous cropping ranged from a loss of $280 to $380 per hectare.

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