Eight new clubroot cases found in Manitoba canola this year

Manitoba Agriculture wants to hear from farmers who suspect clubroot in their fields

The map shows positive clubroot findings by RMs, which have been highlighted to show the highest concentration of spores. This does not mean all fields in the RM have these concentrations. As spore concentrations can be highly variable within a field, the RM classification indicates only the maximum concentration found in any field in the RM. Further explanation on the concentration categories are as follows: RED = Symptoms observed: Clubroot symptoms have been observed in fields in this RM. Management to prevent continued buildup or spread of this pest should be implemented.
ORANGE = 10,001 to 80,000 spores/gram soil: Spores have been found in fields in this RM at concentrations approaching levels known to cause field symptoms. Without management, concentrations may increase to where symptoms are visible.
YELLOW = 1,001 to 10,000 spores/gram soil: Clubroot spores have been found in this RM at low to intermediate levels. With proper management, spore concentrations can decline.
GREEN = zero to 1,000 spores/gram soil: Clubroot spores have not been detected, or detected at very low levels. At this concentration, clubroot is not a major concern, but fields should be monitored. Retesting is recommended within the next five years.
It is generally reported that 100,000 spores/gram of soil are required to see symptoms under field conditions, but symptoms can still appear under favourable conditions.
As less than 10 per cent of farms in Manitoba have been sampled, it is recommended that all fields be tested, regardless of RM classification.

Eight new cases of full-blown clubroot have been found in Manitoba canola fields so far this year but there are likely more.

So farmers should be scouting and reporting suspected infections to Manitoba Agriculture, says Manitoba Agriculture pathologist Holly Derksen.

“I would definitely say we don’t need to panic,” one of the farmers who discovered the disease in his canola said in an interview August 8.

The farmer asked not to be named.

“It’s here and one of the big messages is not to panic and to think of best management practices going forward,” he added.

Crop rotation, planting resistant varieties, reducing tillage and cleaning equipment after working in an infected field are ways to battle the soil-borne pathogen.

Clubroot is regulated as a pest in Alberta, but not Manitoba. The locations of Manitoba farms with clubroot remain private, although rural municipalities where the disease has been found are made public, Derksen said in an interview. (see map at top).

Reporting suspected clubroot cases can help the affected farmers and ultimately all farmers.

“When we come we will soil sample, we will try to delineate the (infected) area with you and we’ll help you with these management practices,” Derksen said. “We’re hoping there is going to be less stigma involved.”

Six of this year’s eight new clubroot infections were found in the RM of Pembina in south-central Manitoba.

Clubroot has been found there before so new cases aren’t a surprise, Derksen said.

But this year for the first time clubroot-infected canola was found in the nearby RMs of Lorne and Dufferin.

Manitoba’s first case of clubroot in canola was found in 2013. In 2014 Manitoba had 13 cases, but 11 were based just on soil samples, with no visible signs of disease in canola.

Previous to this year, clubroot symptoms in canola had been found in only five municipalities — Pembina, Louise, Portage la Prairie, Westlake-Gladstone and Swan Valley West.

This year’s clubroot infections weren’t hard to spot, Derksen said.

One farmer said he first noticed something wrong at the 30 per cent bloom stage. Plants were looking poor. When pulled they had the classic clubroot galls, Derksen said.

In that case, and most of the others there were too many infected plants to pull by hand, she added.

When clubroot shows up in big patches it’s likely the disease has been building over a few years, but went undetected, she said.

When practical, pulling and burning clubroot-infected canola can help reduce future infections, Derksen said.

Although clubroot spores can survive in soil up to 20 years, without a host plant many of them will die sooner. That’s why not planting canola in an infected field for at least two years is recommended, Derksen said.

Farmers should also plant clubroot-resistant varieties of canola too, Angela Brackenreed, the Canola Council of Canada’s eastern Manitoba agronomist said in an interview.

Since the disease is soil-borne farmers can try to work infected fields last and then clean their equipment to avoid spreading the disease to other fields.

Clubroot has also been found in North Dakota this year.

“The message is this is not unexpected (in Manitoba) and manageable and reporting it is super helpful,” Derksen said.

About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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