Unexpected wheat midge outbreaks across Western Canada highlight why the varietal blend remains essential.
As farmers look ahead to spring, it’s a good time to revisit the cornerstone of protecting the Sm1 (midge tolerant) wheat gene: understanding why Midge Tolerant Wheat is sold as a varietal blend. In these blends, a variety of Midge Tolerant Wheat is mixed in with a small amount (10%) of wheat that isn’t tolerant to the wheat midge. That is, it doesn’t contain the gene Sm1, the source of genetic resistance.
These non-tolerant wheat plants serve as a “refuge” to ensure the wheat midge doesn’t develop resistance to the Sm1 gene.
“You never know when the wheat midge is going to strike or where it’s going to strike,” says Tyler Wist, an entomologist with Agriculture and Agri-Food Canada (AAFC). “Sometimes it’s predicted to be a low-risk year, and then the rains come at just the right time and — boom — population explosion.”
Wheat Midge Can Appear When Least Expected
Forecasting tools, including provincial sampling maps in Alberta and Saskatchewan, give farmers valuable early-season insights. But Wist notes that wheat midge biology and Prairie weather patterns don’t always cooperate with expectations.
“We’re monitoring with pheromone traps across much of Western Canada, and we’ve seen years where the models tell us to expect no midge at all. Then the conditions line up, and suddenly we’re dealing with very high numbers.”
This unpredictability is exactly why the refuge — even in historically low-pressure regions – remains essential.
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