Resistant clubroot a ‘nightmare’ scenario

Continuous cropping likely cause of new resistant clubroot pathogen, 
but canola council says tight rotations are still OK for some

The breakdown of a clubroot-resistant variety just four years after it came on the market is a “nightmare” — but doesn’t mean growers in clubroot-free areas can’t plant canola every other year, say industry officials.

“It’s unfortunate that this had to happen,” said Ward Toma, general manager of the Alberta Canola Producers Commission.

“We had a tool in resistance and it’s a nightmare that it broke down so fast. And it broke down so fast because it was not used properly, from what we understand.”

Late last summer, several growers in the Edmonton area who planted resistant varieties developed in 2009 reported finding dead patches and infected plants in their fields.

“We were hoping that we would get maybe eight to 10 years from the current sources of resistance but we got four,” said Clinton Jurke, agronomy specialist with the Canola Council of Canada. “But that’s not to say that all resistance has failed out there.”

Man in suit and tie

A two-year rotation is OK, as long as you aren’t in a clubroot-infested area, says Ward Toma, general manager of Alberta Canola Producers Commission.
photo: Supplied

The canola council came under criticism earlier this year from some, including the past chair of the Saskatchewan Canola Development Commission, for backing tighter rotations in some circumstances. In announcing a new target of 26 million tonnes of production by 2025, the council released a document stating crop insurance data showed “in many areas, growers are maintaining canola yields while growing the crop more frequently.”

A minimum one-in-four-year rotation is still recommended for clubroot-infested fields, but many farmers find themselves in a grey area.

Round Hill grain farmer Humphrey Banack is one of them.

His farm is 80 kilometres from Leduc County, a clubroot hot spot. Banack and his brother, who runs a custom spraying operation, keep their equipment clean and ensure oilfield equipment coming onto their land is clean, too. They also avoid clubroot-infested fields, and rigorously scout their crops for signs of the disease.

Clubroot has come to their county, but so far they haven’t found any on their land. Still, Banack plans to plant resistant varieties for the first time.

“We wanted to try it out this year and see how it performs,” said Banack, who is vice-president of the Canadian Federation of Agriculture. “If there are small amounts (of clubroot) out there, maybe it will provide us a yield benefit.”

About 45 per cent of his acres will be seeded to canola, with the rest divided among wheat, pulses, and flax.

Some of his fields are on three-year rotations, but most are on a canola-wheat rotation.

Man in coveralls

Humphrey Banack practises due diligence and knows about the danger of living in a clubroot-infested county.
photo: Supplied

“There is more return from a canola and wheat rotation, than there would be if we went to a four-year rotation,” he said. “It’s harder for us to compete with a land base if we’re being more cautious for clubroot.”

What’s more, he notes, a two-year rotation has been deemed acceptable by the canola council.

And while Banack is adhering to the council’s recommendation of “more intensive monitoring and management of diseases and insects” when using tight rotations, some wonder if enough farmers are doing the same.

“They’re assuming that with all our tools, we should be able to manage risk,” said Murray Hartman, oilseed specialist with Alberta Agriculture and Rural Development.

“That may be overplaying the role of new varieties and new products, and downplaying the role of cultural tools, like rotation. Not everyone agrees with that message.”

And since no one knows how quickly new strains of resistant clubroot might appear, longer rotations might be a better path to follow, he said. With a one-in-four rotation, resistance might last eight or 10 years, and give breeders more time to create new resistant varieties.

“We’re not prepared with more resistant varieties,” he said. “Now there’s guys with resistance breaking down, and we don’t have anything to offer them.”

And farmers should not be gambling with resistant varieties, he said.

“Guys who have clubroot on their field shouldn’t be growing a resistant variety more than once every four years,” said Hartman.

The canola council agrees.

“We don’t want this resistance to be lost in a short amount of time, but it looks like not all growers were heeding that recommendation,” said Jurke.

His organization is only saying shorter rotations work in areas where there is not a concern about disease or pest issues, he said.

“What we had communicated a few months ago was that we were encouraging growers to accept a rotation that could be the best for them, on the basis of what their risk thresholds are,” he said.

“A two-year rotation is OK if you’re not in the blackleg zone or the clubroot zone,” added Toma. “If your risk of disease from pathogens and insects is very limited, then a two-year rotation or break is probably OK.”

But the only way you can know that for sure is through constant and in-depth scouting, said Banack.

“Producers have to be very aware of whether or not they have it,” he said. “We can’t bury our heads in the sand and say we won’t have it if we don’t look for it.”

He hopes that’s the case in his area.

“If my neighbour had clubroot, I think it would be virtually impossible to contain because it could be spread through birds or animals or mud on a field,” he said.

Among the canola council’s recommendations are rotating resistant varieties, scouting fields seeded to other crops (since volunteers and susceptible weeds can harbour clubroot), and scouting right up to swathing.

Meanwhile, University of Alberta plant pathologist Stephen Strelkov, who confirmed the existence of the new clubroot pathogen this spring, will be using it to try to infect all commercially resistant varieties to see which ones are still functioning. At this point, no one knows how widespread the new pathogen might be.

About the author

Reporter

Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."

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