In the fall of 2015, clubroot galls were discovered in a canola field near Swan River, Man.
It was the first confirmed case of clubroot with visible symptoms of the disease in Manitoba.
Three years later, more than 30 canola fields in Manitoba have plants with clubroot galls, and the cases have spread well beyond the Swan River Valley
“There are 33 fields confirmed with visual symptoms; 15 new fields found in 2018,” said Anastasia Kubinec, manager of crop industry development with Manitoba Agriculture.
“In other provinces, Saskatchewan found 37 fields with symptoms in 2018…. Not sure on what Alberta found, but unfortunately if it’s like past years, it is usually 200 plus fields a year that they find.”
Clubroot is a soil-borne disease that causes swellings, or galls, to form on the roots of canola plants. The galls cause the plants to die prematurely. The disease spreads when contaminated soil or plant debris is transported from field to field.
The disease first appeared in the early 2000s, when it was found in canola fields in central Alberta. In certain Alberta counties there are regulations on how often growers can plant canola because more years between canola can reduce the population of clubroot spores in the soil and minimize the impact on future canola crops.
For the last 15 years, many canola growers in Manitoba viewed clubroot as an Alberta problem. Now that 33 fields have visual symptoms, the disease is getting harder to ignore.
“It was a surprise to me when I first heard it (in 33 fields),” said Chuck Fossay, president of the Manitoba Canola Growers Association. “It wasn’t something that (was) widely known.”
Manitoba Agriculture reported this summer that the province has two hot spots for clubroot. One is the Swan River Valley and the other is the rural municipalities of Louise and Pembina in south-central Manitoba.
A clubroot distribution map shows that six municipalities in central Manitoba have observed symptoms of clubroot, which means more than 80,000 spores of the disease per gram of soil.
In the RMs of Louise, Pembina and Swan River, most canola growers are at high risk for clubroot, Holly Derksen, former Manitoba Agriculture field crop pathologist, said this summer.
“Just assume you have clubroot. And if you don’t, you’re going to have it soon.”
Despite such comments, many Manitoba growers remain nonchalant about clubroot.
“To be honest, most of the producers that I’ve spoken to — the concern in Manitoba has always been very low,” said Fossay, who farms near Starbuck, Man.
“It might be a higher profile concern when you find it on your farm or when your neighbours have it. I just know that most producers … it’s sort of like until it hits me, it’s not a problem I’m going to worry about.”
Manitoba producers probably aren’t concerned about clubroot because canola yields were good to excellent this year. Even with a hot, dry summer, the average canola yield in the province could be 45 bushels per acre.
Clubroot still poses a risk to future yields, so the MCGA plans to take action this winter.
At a board meeting in mid-November, Fossay will propose a series of workshops on clubroot, particularly in regions that are hot spots for the disease.
“Talk about the disease … (and) promote the best management practices that are recommended,” Fossay said.
“Whether it is longer rotations (and) using clubroot resistant varieties.”
Clubroot resistant varieties likely saved many canola growers in Alberta, who otherwise couldn’t grow the crop because of high spore levels in their soil, but the disease is evolving in the province.
New and more virulent strains of clubroot have appeared, and they are overcoming genetic resistance to the disease.
Scientists are worried that growers have relied too heavily on genetic resistance as a single tactic, causing the disease to evolve more rapidly than expected.
“It’s definitely of concern,” University of Alberta plant pathologist Steve Strelkov said earlier this year.
“Genetic resistance is by far our most effective and important clubroot management tool.”