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Battling to stay ahead of clubroot

The number of confirmed clubroot cases in Western Canada continues to grow, but if clubroot is discovered early, the disease can be managed much more effectively with minimum impact on the canola yield.

Clubroot prevention

Clubroot is a soil-borne disease that causes galls to grow on the roots and prevents the canola plant from getting vital water and nutrients.

Washing equipment, or at least knocking most of the dirt off, prior to storage and, in summer months, between fields, is a must to prevent spread of clubroot spores, says Dan Orchard, an agronomy specialist with the Canola Council of Canada.

"Equipment is the major mode of clubroot transmission," Orchard says. "The risk of spreading clubroot is reduced by the amount of soil removed before entering a field. If 90 per cent of the soil is removed, so is 90 per cent of the risk."

Michael Harding, a plant pathologist with Alberta Agriculture, says planting clubroot-resistant canola is another effective management tool. However, when it's overused, resistance will break down.

"If we continue to grow resistant cultivars in fields that have high resting spore populations, the resistance erodes in just three cycles of canola," Harding says.

A recent University of Alberta survey indicates over 170 fields in that province have some resistance issues.

Harding also stresses the importance of crop rotation.

While the recommended rotation for canola is once every three or four years.

"If we want to contain this, we need to think carefully about crop rotation and equipment sanitization," says Harding. "Those are the two management principles that are really going to either help us to avoid contaminating new fields and/or manage it in the fields where it is already found."

Treatment options

Experts say heavily-infested areas and hot spots should be seeded into a grass species. Orchard says the grass appears to coax clubroot spores out of dormancy and helps to reduce spore loads more quickly. The grass also identifies the clubroot location so traffic can avoid the area.

Liming areas of the field to increase pH can help, he says, but it needs to be done properly since raising pH too high could also lower yield.

Fumigation and/or solarization also appear to work, but Orchard adds it is difficult and expensive, even for small areas.

The Canola Council of Canada and the Saskatchewan Ministry of Agriculture have more detailed clubroot management and prevention information.

2018 incidents

A new clubroot map from Stephen Strelkov, a University of Alberta professor of plant pathology, reports 3,044 confirmed clubroot cases since the initial discovery 15 years ago near Edmonton. Another 300 new clubroot cases were found this year. Most of the new cases, however, are near other previously confirmed fields.

Clubroot is far less common in Saskatchewan and Manitoba, but the numbers are growing. Clubroot symptoms were identified on 37 fields in Saskatchewan and 33 in Manitoba.

The Saskatchewan Ministry of Agriculture is expected to release a coverage map in early 2019.

Meanwhile, there were 15 new clubroot cases confirmed in Manitoba in 2018.

"This is a jump from previous years, likely due to increasing vigilance when scouting, coupled with a dry summer," says Dane Froese, Manitoba Agriculture oilseed specialist.

Source : fcc