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Agronomists see Significant Losses from Aster Yellow

Courtesy of the Manitoba Government

What’s your view on aster yellows? Is it a serious, uncontrollable disease that could threaten Canada’s multi-billion canola crop? Is it a cyclically appearing problem with no control options anyway, diverting attention from more pressing agronomic issues?

While Doug Moisey hears a variety of opinions out there, he’s personally more inclined to the second view.

“This is a disease that comes in from the U.S. Midwest,” explains Moisey, Area Agronomist with DuPont Pioneer based in St. Paul, Alta. “The virus travels in the saliva gland of leafhoppers. This year, it was a perfect year in terms of the strong winds needed to bring the leafhoppers northward in large numbers and when the drought in the U.S. took out their food supply, large numbers came in.”

On his own travels this past growing season, Moisey saw evidence of aster yellows in just about every field he visited. Canola growers from Manitoba to the Peace reported it. Still, getting a handle on the extent of the damage and yield loss caused by aster yellows isn’t so easy.

Moisey spoke with growers who attributed 1% to 2% yield losses to aster yellows. Other producers pegged their yield loss from 5% to as much as 10%. That’s worrisome, but considering the nature of the threat, Moisey recommends a measured response.  

“You see this disease once every five or six years in a significant way,” he says. “In the 20 years I’ve been working in canola, I've seen this kind of aster yellows situation maybe four or five times. There’s also nothing available for control of the disease. Some researchers have suggested planting early to get around it, but that can cause problems too.”

According to Dan Orchard, growers will have to perform their own due diligence on aster yellows.

“Many farmers across the Prairies are looking for answers as to why their 2012 canola crop wasn’t as good as they expected,” says Orchard, the Canola Council of Canada’s Agronomy Specialist for Central Alberta. “Although some areas were hit pretty hard by sclerotinia, and many regions by extreme heat at a vulnerable time for the crop, some growers are convinced these factors aren’t responsible for their lower yields. So there’s not a lot to point the finger at, other than aster yellows.”

Aster yellows will be a topic of canola conversations all winter. The likelihood of a repeat performance in 2013, though, may be relatively low. That, of course, will depend on conditions next year. To Orchard, the hit-and-miss nature of this disease frustrates farmers and has also hindered research progress.

“The previous year where we had had higher-than-normal levels of aster yellows was 2007,” he says. “The next year, researchers went out to try to get a handle on aster yellows, and there was very little impact from the disease. With everything that happened in 2012, though, I’d have to think more people will be working on this. So for growers, it’s case of hold tight and trust the research community to look into it.”

With all the discussion of aster yellows, Moisey would like to see more done about other, more persistent canola diseases that continue to pose problems for growers.

“With the amount of canola I saw this past season with sclerotinia, blackleg and clubroot,” he says, “those are diseases that we can work on managing, and more attention on those diseases is needed.”

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