Clubroot's reach is growing in east-central and northern Alberta. The disease infected fields in three new counties this year, according to the Canola Council of Canada.
Beaver County, east of Edmonton, is one of the municipalities reporting clubroot for the first time this year.
"We're still continuing our surveying but so far it has been just one field," said Krista Kotylak, assistant agricultural fieldman with the county.
The county will follow the Alberta Clubroot Management Plan and will restrict canola growth in infected fields for four years, Kotylak said.
Quinton Beaumont, ag fieldman for Stettler County -- which surrounds the town of the same name -- says the county now has three confirmed cases.
The county will place a five-year restriction on canola and other crucifer crops in infected fields. Farmers will also need to control any host weeds. After five years, canola can be grown once every four years. Resistant varieties must be grown, and farmers must rotate resistant varieties.
Though clubroot is spreading, it's manageable, he said.
"If guys follow these guidelines set out by the county and our ASB (ag service board) members, they can have one per cent infestation in their field, which is no different than having sclerotinia or yellow asters," he said. "They can get to the point where it's manageable.
"If we don't follow the guidelines, yeah, it's going to spread like wildfire."
The name of the third new county reporting clubroot hasn't been confirmed, but there are now at least 22 Alberta counties with clubroot cases.
The number of infected fields in each county varies greatly. Sturgeon, Parkland and Leduc have more than 45 fields each, while some others have between one and nine infected fields.
It's in farmers' best interests to scout for clubroot, Beaumont said. Harvest is a good time to pull out a few stalks from areas that look suspicious.
Stettler County has staff that will help farmers identify clubroot, he added. Farmers can also send samples to an accredited lab without the county's help.
"The more eyes looking for it, the better off we are. We may find more infestations, but we won't spread it as much because we know where they are."
Clubroot is established in Canada mainly in vegetable-producing regions of British Columbia, Quebec, Ontario and Atlantic Canada. The disease turned up in canola in Quebec in 1997.
Even after several decades of large-scale canola production in Western Canada, clubroot didn't hit Prairie canola until it showed up in spots near Edmonton in 2003 and began moving east.
Traces of clubroot DNA were spotted in soil samples from a west-central Saskatchewan field in 2009 and in two unrelated fields in Manitoba in April this year. The clubroot pathogen was confirmed in two separate fields in north-central Saskatchewan in 2011.
Warm soils, high soil moisture and low soil pH favour the spores' germination, infection and development. Once the clubroot microbe infects a host plant, it alters hormone balance and speeds up cell division and growth in the roots, creating deformed galls.
The galls prevent a canola plant's roots from taking in nutrients and water, cutting yields on average about 25 per cent. The pathogen can lurk in the soil for up to 20 years.
-- Lisa Guenther is a field editor for Grainews at Livelong, Sask. For more information on managing clubroot, visit Clubroot.ca or check out the Oct. 22 edition of Grainews.