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New blackleg diagnostic test available this fall

A new diagnostic test will make it easier for producers to match the right kind of blackleg-resistant seed to the specific race in their fields

There are things you can do this fall to reduce your risk of blackleg next spring — and the first step is to scout for it.

“The more you can identify it, the more you’re going to know whether you’re successful at controlling it,” said Clint Jurke, agronomy director for the Canola Council of Canada.

“When you know what’s killing your plants, you can make plans for it the next time you put canola in that field.”

Blackleg became a trade issue between Canada and China in 2010, mainly because China does not yet have the blackleg pathogen in its own canola crop. The risk of spreading the disease from Canadian canola to Chinese is “fairly low,” but the “trade dispute between the two countries persists,” particularly since the levels of blackleg in Canada have been on the rise since 2010.

“In the last round of trade negotiations, the way we were able to keep that $5-billion market open is that Canada has committed to reducing the amount of blackleg infection that we have here,” said Jurke.

“What we need to do is come up with a new strategy to bring that blackleg level back down so that we can keep the trade flowing and remain profitable as a canola industry.”

One of the best times to scout for blackleg is in the fall, said Jurke, who spoke at a CanolaPALOOZA pre-harvest event in late August. During swathing or combining, producers may spot some lodging, and when the stems are cut, the blackened tissue inside the crown of the stem is easy to see.

And once blackleg has been identified, “genetics and rotation are our best controls.”

“When resistant genetics came into play in 1995, the blackleg incidence dropped right off. Resistance works fantastically, but crop rotation is your other big control mechanism,” said Jurke.

Canola residue can take four years to decompose completely in the field, and “that’s where the fungus hides out,” he said.

“In the intervening years after you’ve grown that canola crop, it starts shooting spores out and that’s what infects your crop,” said Jurke.

“If you’re on a four-year rotation, most of this canola residue completely decomposes, and therefore, you don’t have a blackleg problem.”

While resistance has been “working really well” up to this point, a resistance label on a bag of seed may not paint an accurate picture of how that variety will work in an individual farmer’s field.

“Those R ratings are an average of how that variety performs across the entire Prairies,” said Jurke. “It gives you an idea of how stable it is, but on your particular farm, it doesn’t necessarily mean it’s going to be R rated.”

Complicating matters further, each resistant variety will have a specific resistance gene, which then has to match up with a particular race of fungus in the field.

“If that resistance gene cannot recognize that the fungus is in your field, that resistance doesn’t work,” said Jurke. “The ideal system is to match up your particular resistance gene with the particular race that you have in the field.”

A new voluntary resistance labelling system has been launched this year, and some seed companies are now labelling their bags with the type of resistance found in the seed.

“It will tell you what resistance gene is in that variety so that you can pick which one is going to be best,” said Jurke.

“Say you had a disaster of blackleg. You can look at the variety and say, ‘Son of a gun, the resistance didn’t work. I know it was resistance gene C that I had in this variety. Next time I plant canola in this field, I do not use resistance gene C because it doesn’t work.’”

But what happens if you don’t know which resistance gene was in your last variety?

“There’s a new tool that’s coming online right now at some of the diagnostic labs where you can take your old canola residue and send it into the lab,” said Jurke, adding that those tests should be available later this year.

“They’ll screen it with genetic markers and tell you exactly which race you have, and then you can choose which resistance gene is going to work the best.”

So when making next year’s cropping plans, producers who have identified blackleg in their fields should consider stretching out their rotations, have their residue tested, and select the right seed to combat the disease in their field.

“If we have blackleg, we can start bringing that back down,” said Jurke.

“When you reduce the amount of blackleg, you have better yield, and it makes sure our trade continues so that the industry can remain profitable.”

This article first appeared on the Alberta Farmer Express.

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