The rapid spread of clubroot in the last decade will continue in the coming one if canola growers don’t start to get ahead of the disease.
“The resistance is being overcome already, and some of those cases are pretty significant and serious infestations,” said Dan Orchard, agronomy specialist with the Canola Council of Canada.
“In a way, it’s kind of like when clubroot was first being found, when we didn’t have resistance. It reminds me of that.”
While China’s canola ban dominated news about the crop in the past year, the devastating pathogen continued its relentless assault on farmers’ most valuable crop.
Its spread in 2019 followed the same pattern seen in the last decade, with around 300 new cases cropping up in Alberta over the past year. University of Alberta researchers have identified 36 different pathotypes of the deadly disease and more alarmingly, found some that overcame the first round of resistance are “really ramping up.”
“I’m nervous because I’ve been to fields seeded to resistant varieties that are really, really quite heavily infested with a new strain,” said Orchard.
“I suspect that, out of a lot of the new cases, we’re going to see a shift in the pathotypes in a lot of these fields that have had too many cycles of resistant varieties where the spore loads are too high.”
The disease is also spreading to parts of the province where it hasn’t historically been an issue.
“That happened again this year, but in a way, it shouldn’t,” he said. “They probably wouldn’t have discovered such big patches and developed such a problem so quickly if they had deployed the resistant varieties sooner and moved to longer intervals between canola crops.
“All of these counties on the fringe and even outside the fringe areas need to be using resistant varieties earlier than they are.”
While Orchard has started to see producers extending the popular, but risky, two-year crop rotation to three (or even four) years between canola crops, that change is happening slowly.
“It’s like anything else — until you’re really affected, you don’t really do anything about it. That’s not the right way to manage clubroot,” he said.
“I don’t think the message is clear enough and strong enough to the bulk of the Prairies that don’t have a problem yet that they need to proactively manage this and not just wait for it to arrive on their farms.”
But in the heart of clubroot country near Edmonton, farmers have got serious and it’s working to keep the disease at bay.
“The farmers who are doing this don’t even know if they have clubroot,” said Orchard. “They’ll tell you that they do — it’s endemic in their area — but they don’t know where because it’s manageable on their farms.
“These are people who don’t have issues with clubroot even though you would expect them to. It’s quite manageable when that proactive approach takes place.”
That’s what happened on John Guelly’s farm after he learned he had clubroot seven years ago.
“We went through the five stages of grief, but finally started making some changes four or five years ago,” said the Westlock-area farmer.
“I haven’t seen expression on our farm for several years, and that’s mostly attributed to lengthening our rotation — getting back to a two-year break — growing resistant varieties, and cleaning soil off between fields. It’s been quite the journey.”
But for Guelly, the hardest part of managing clubroot was dealing with the stigma that comes with it.
“People don’t want to talk about having it, and if they don’t want to talk about having it, there’s not usually much done on the farm to prevent further spread,” he said.
“It is definitely a horrible disease, but it’s something that is manageable. Once I came around to that way of thinking, it wasn’t such a big thing as I originally thought it was.”
Typically when a farmer finds out they have clubroot, “they really up their game,” said Orchard, but at that point they’re facing an uphill battle.
“The bulk of the Prairies needs to understand that they need to take a proactive approach — start rotating crops, using resistance, reducing soil movement, and controlling host weeds and volunteers — rather than waiting for clubroot to arrive,” he said.
“With a proactive approach in the bulk of the Prairies using this clubroot recipe we’ve designed, I honestly believe that clubroot wouldn’t be an issue.”
That’s not to say it will stop spreading because spores travel easily. The key is to keep spore loads as low as possible.
“The clubroot management recipe — the five or six things that growers need to do — is like getting the flu shot. You don’t wait until you have the flu to get the shot. You do it beforehand,” said Orchard.
The first step is scouting, even in fields seeded to a resistant variety (something that will be increasingly important as resistance continues to break down). And if you’re not already growing a resistant variety, it’s time to start.
“It’s a no-brainer,” said Guelly. “Even if you don’t think you have clubroot, there’s really no downside to it.”
Another step is to avoid planting canola in areas where there’s a risk of clubroot being introduced, particularly where there’s heavy traffic (such as field entrances).
And limiting the movement of soil on equipment is also key.
A complete three-stage sanitation process is often “a little bit unrealistic,” Orchard admits, but not making any effort to clean equipment is highly risky. Guelly doesn’t fully sanitize his equipment — a three-hour process — but does take time to knock off the majority of the loose, visible dirt.
“Just going around and knocking dirt off shanks and tires probably does 90 per cent of the job,” said Guelly, adding it only takes about 10 minutes if it’s not muddy.
“When they think about sanitation, they’re thinking about a fine toothbrush and soaking it in bleach,” added Orchard. “That would be an extreme case. Taking 15 or 20 minutes at the end of each field is reasonable, I think.”
Extending the rotation is a tougher sell.
“The bulk of the Prairies have been on a two-year rotation for years and years, and it’s a very successful, easy rotation until problems like this arise,” he said. “It’s just a change of mindset now to get away from that two-year rotation that’s been so successful and easy for 20 years now.”
But it doesn’t have to happen all in one year — and in fact, it likely won’t, Orchard added. Some growers who have made the change say that it takes between three to five years to switch completely.
“If you’re on a two-year rotation, get it in the back of your mind now that you need to extend that before clubroot arrives,” he said.
“For those folks who are outside the clubroot region, I do believe clubroot will be coming their way eventually, and I think they need to understand that it won’t impact their farm hardly at all if they do begin this three-year rotation with resistant varieties.”
Inevitable, but manageable
Even so, it’s likely that most — if not all — canola farmers in Alberta will have a brush with clubroot over the next decade, if they haven’t already.
“I think it’s just a matter of time until the management practices are deployed by everybody growing canola. It’s just unfortunate it’s taking some time to get there,” said Orchard.
“Canola pays the bills quite well, so I think they’ve just been kind of complacent waiting for clubroot to arrive before they address it. Hopefully, we can shift that mindset and get growers doing all the things they can before it arrives.”
And it doesn’t have to be an overnight switch, he added.
“We like to say, ‘It’s OK if you can’t do everything, but it’s not OK to do nothing.’”
And even if clubroot feels inevitable — as it almost certainly is — and even if it can’t be eradicated completely, it can be managed.
“Farmers do need to take it seriously,” said Guelly. “Canola is one of the more profitable crops for most farmers, so we certainly need to get a handle on it. We’ll never be able to eradicate it, but we need to find it early when spore loads are low and try to slow down the spread as much as possible.”
“In a way, I’m nervous about the spread, but I still have confidence that, by getting ahead of the game and proactively managing this, we still have a pretty good opportunity to keep it from exploding even more.”