BROOKS, Alta. — Clubroot has long been an international traveller and continues to be a domestic tourist as it spreads further into agricultural regions.
As he trod through the clubroot disease nursery west of Brooks, Alta., July 31, Alberta Agriculture plant pathologist Ron Howard mused on how the parasitic root disease came to Canada, quietly spread and became a yield-limiting factor in canola, one of the country’s most important crops.
Clubroot is thought to have arrived in Canada from Europe with early settlers. It was noted in Ontario and British Columbia vegetable crops in the early 1900s.
It likely made the leap to the Edmonton area aboard vegetables and flourished in garden plots with members of the brassica family, including cabbage, cauliflower and broccoli.
Its unwelcome presence in Alberta canola was discovered in 2003.
“It might have started in market gardens there and on farms and as homesteads were abandoned and those areas were worked into the field, it just eventually spread,” said Howard during a “canola galla” crop tour.
“We think it was in canola much earlier than 2003, but it went undiagnosed because it was missed. You’d think we would have noticed it before, but … nobody was digging around looking at roots that much.”
The disease has now been confirmed in 1,064 Alberta fields across 24 counties as of November 2012. It has also been found in Saskatchewan and Manitoba.
Victor Manolii, a researcher with the University of Alberta, said clubroot dates back to 4th century Roman times, proof of its hardiness and ability to spread.
“Once infected, it is almost impossible to eradicate,” said Manolii.
In Canada, the disease was first reported on canola in Quebec in the late 1980s. Its rapid spread on the Prairies since 2003 is due to the equally rapid increase in canola acres. The shift from open pollinated varieties to hybrids may also be a factor.
“It could be that the hybrids were susceptible, so it just showed up at a greater rate,” Howard said.