Canola School: New Canola Disease Found in Six Provinces

Canola infected with verticillium wilt (photo courtesy MAFRD)

Editor’s note: The Canadian verticillium stakeholders committee has decided to call the disease caused by Verticillium longisporum “verticillium stripe” instead of “verticillium wilt.” This story has been updated to reflect the new terminology.

The canola industry is in the early stages of understanding what it’s up against with a new fungal disease. Verticillium stripe (previously called verticillium wilt) — first detected in Canada in a research plot in south-central Manitoba in 2014 — has been found on canola in six provinces.

The Canadian Food Inspection Agency surveyed 1,074 fields across the country in 2015 for verticillium stripe — specifically, Verticillium longisporum. Stem and root samples were tested at the CFIA’s National Plant Pathology Lab in Ottawa in January and the results from the survey were recently posted on the CFIA’s website.

While the majority of the samples were collected in the prairie provinces, the survey found at least one field with canola infested by the disease in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, and Québec. Verticillium stripe was not detected in samples collected from New Brunswick, Prince Edward Island or Nova Scotia.

Verticillium longisporum is a serious disease threat to rapeseed crops in Northern Europe, so what do these survey results mean for Canadian canola growers?

“It basically means canola growers have one more disease to worry about,” says Pratisara Bajracharya, field crop pathologist with Manitoba Agriculture, Food and Rural Development, in this episode of Canola School. “It’s found in six different provinces, but they also mention it doesn’t seem to be causing any significant yield loss yet, so that’s good news.”

The survey was designed to look at distribution, not concentration, she explains, so it’s too early to assess the potential impact verticillium wilt could have on canola production.

While there will be some field trials at sites where the pathogen has already been found in 2016, in-depth research to understand the disease and its implications is on hold until the CFIA determines its regulatory status — whether it should be considered a regulated pest, she says.

The agency is drafting a document outlining regulatory options which will be published for stakeholder comment in the coming months. The CFIA did not have a spokesperson available to comment on the timeline, but said in a statement that “the outcome of the risk management document considerations and consultation will be a final decision regarding the regulatory status of Verticillium longisporum in Canada.”

“Once that is done, there would be more areas of research open regarding this pathogen,” explains Bajracharya, noting it has been added the list of diseases monitored in the annual canola disease survey.

In the meantime, she says growers should follow the same practices used to manage clubroot disease, since verticillium stripe is also a soil-borne pathogen.

“Anything you do for clubroot — biosecurity practices involving cleaning your equipment (restricting soil movement) and crop rotation — will definitely help with managing this disease,” she explains, noting there are no known resistant varieties grown in Canada and no foliar fungicide or seed treatment that’s registered against Verticillium longisporum in Canada.

When scouting in-season, watch for early-maturing or stunted patches — also similar to clubroot, suggests Bajracharya, Diagnosing the disease can be difficult, as brown striping on the stem is an indication of verticillium stripe, but it’s also a symptom of and can be found on the same plant as fusarium wilt. Blackleg may also be confused with verticillium stripe.

The best time to scout for Verticillium longisporum is at harvest or shortly after, she says.

“At that time, the pathogen is forming microsclerotia on the stem, and it’s more distinguishing at that point,” Bajracharya explains, suggesting growers and agronomists submit suspected samples to a lab to confirm.

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