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Disease a North American first

Where it came from isn’t as important as how it will be contained when it comes to verticillium wilt in canola

Manitoba prides itself on welcoming newcomers, but the canola sector won’t be rolling out the welcome mat for this one — verticillium longisporum.

The disease was discovered in a Manitoba canola field late last fall and visually identified at Manitoba Agriculture’s Crop Diagnostic Centre. That determination was later confirmed by molecular analysis at the National Fungal Identification Service in Ottawa.

“This is brand new to Manitoba, brand new to Canada and actually brand new to oilseeds in North America,” said Holly Derksen, speaking at St. Jean Farm Days last week.

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But how the fungus, which is prevalent in Sweden and seen throughout Northern Europe, ended up in Manitoba may remain a mystery.

“I don’t think we’ll ever figure it out… the spores are tiny, they’re like dust particles, so it’s not going to be a matter of tracing it; at this point we just need to figure out what to do with it, because it’s here,” said the field crop pathologist.

Now Manitoba Agriculture is working with the Canadian Food Inspection Agency to determine if the disease is widespread, or if the site in question is an isolated case.

Undisclosed location

Provincial officials say they will not release the location.

Holly Derksen

Holly Derksen speaks about verticillium longisporum at St. Jean Farm Days.
photo: Shannon VanRaes

“We’re not even releasing the region because we don’t know yet if it’s a specific isolated event that we’ll be able to control on the farm and be done with, or if it’s more widespread,” Derksen said. “At this point we’ll treat it much like we did with clubroot in the beginning, where we don’t release information until we figure out how widespread it is.”

She noted that the site in question was not experiencing yield loss, but was tested after the producer noticed signs of disease while scouting.

The Canadian Food Inspection Agency said Jan. 9 it has placed a quarantine order on seed from the farm. A prohibition of movement order is also in place on equipment used to harvest the seed, CFIA said, adding it’s working with the farm’s owner to discuss “treatment options” for said equipment, to make sure it’s cleaned of soil and plant debris.

The agency said it’s still too early to know the source of the fungus, but CFIA is running trace-outs to learn how V. longisporum arrived at that spot.

CFIA said it also plans related surveys to rule out any further spread and to learn if this was an “isolated detection” that may have been brought into the location on imported seed.

V. longisporum is mainly spread via movement of infested soil or diseased plant parts, CFIA said, noting “some scientific evidence” that seed from heavily infected crops may bring it to new areas.

In this case, the agency said, the single V. longisporum finding is “limited to one location which is not being used for commercial production.” The Reuters agency and other media have described the site as a research farm.

“Given we are now in the post-harvest season and all crop material has been removed, and that CFIA biosecurity restrictions have been applied at the farm, there is no immediate risk of any further agricultural-related spread of V. longisporum,” the CFIA said.

Scouting urged

The Canola Council of Canada is now urging all producers to scout for the fungus, but acknowledged that few facts are currently available on the disease.

“We will focus on collaborating with regulators, researchers and grower groups to determine its prevalence and bring best management practices to growers,” said council president, Patti Miller.

It has not spread to Canada’s commercial crop-handling system, Miller said. Like clubroot, another disease that affects canola, verticillium spreads mainly from field to field through soil on machinery, boots or other carriers. It can survive in the soil for 15 to 20 years.

“Although it’s disappointing that a new disease has been identified, it shows that the system is working and the industry is responding in a proactive and collaborative manner,” Miller added. “The canola industry has a long history and significant experience in working together to control diseases and pest issues as they arise and this collaborative approach will continue.”

Information on the disease has already been posted to Manitoba Agriculture, Food and Rural Development’s website, and more information regarding research will soon be made available through the canola council, as well.

Symptoms of verticillium longisporum include chlorosis of lateral branches or leaves, often on only one side of the plant and early death stunting. At later stages, the outer stem may peel back to reveal black microsclerotia.

“It’s a black peppering of spots you’ll see right below the surface,” Derksen said.

The best time to scout for verticillium wilt in canola is at swathing, but it can also be identified after harvest as microsclerotia continue to develop.

Rotation

The plant pathologist said crop rotation can help to manage the disease and keep fungi at low levels, but noted there are no fungicide treatments for it or verticillium-resistant canola varieties on the market.

“It’s a difficult one to nail down the resistance for,” she explained, adding the fungi can survive in the soil for 10 to 15 years. Biosecurity practices similar to those used for clubroot are advised.

Sweden has seen the biggest impacts from the disease, with yield losses up to 50 per cent.

“They’ve had it for 30-plus years, so there are things we can learn from them, although their production practices are quite different than our own,” said Derksen. “There are still a lot of things we don’t know.”

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