Researchers at the International Clubroot workshop in Edmonton in June told delegates that clubroot likely had its wild origins in sub-Saharan Africa.
Geoffrey Dixon, a professor at the University of Reading in the U.K. said, “It was not until man really started to use the Brassicas that it evolved.” The Brassica group of plants includes canola and related weeds, but also vegetable crops such as cabbage, broccoli, Brussels spouts, turnips and radishes.
Clubroot evolved in Western Europe, Dixon said, “and from there it has spread to the rest of the world.”
It is not a new problem. Researchers have found reference to a disease that seemed to behave like clubroot in documents written by the Romans, about 2,000 years ago. “At least we think this is what they were talking about,” Dixon said.
Clubroot didn’t emerge as an important problem until the agricultural revolution. In the late nineteenth century, after a severe epidemic hit cabbage crops, Russian scientists set out to learn more about clubroot. One Russian scientist, Mikhail Voronin, managed to identify the importance of rotation, removal and burning to prevent the spread of clubroot.
Dr. Stephen Strelkov, plant pathologist at the University of Alberta, suspects that clubroot was brought to Canada with infected fodder turnips. It was well established here by the late nineteenth or early twentieth century.
Holly Derksen, plant pathologist with Manitoba Agriculture, Food and Rural Initiatives, says there are reports of clubroot in Manitoba vegetable crops dating back to 1925.
By the 1970s, Dixon said, agricultural advisers were telling growers with clubroot problems: “You don’t grow brassicas for five years. End of story.”
But then, Dixon said, “Research really took off from the 1980s onwards.”
In canola, clubroot was first reported in Quebec, in 1997.
On the Prairies, clubroot was first found in canola in 2003, near Edmonton. That year, Dan Orchard, now an agronomy specialist with the Canola Council of Canada, was working as an agronomist. A new graduate, Orchard had studies clubroot at university.
When one of his clients called Orchard out to his field to diagnose a disease, Orchard thought he recognized clubroot. But when he talked to experts, he was told “that isn’t clubroot. We don’t have clubroot.”
But Orchard persisted, and soon found a researcher who agreed with him. Then he took a plant pathologist to visit the infected field. It was like a horror movie for a pathologist,” Orchard said. “Every single plant we pulled out was infected.”
Clubroot was ultimately found in 12 Alberta canola fields that year.
Once it was first reported, experts’ initial assessment of how fast the pathogen would spread turned out to be very wrong. Previously, clubroot had been found in small, intensive horticulture crops. It can spread a lot more quickly in large field scale crops.
Clubroot was found in Saskatchewan in 2008.
By 2009, clubroot resistant canola seed was available for farmers in infected areas.
Infected canola plants were found in Manitoba in 2012 (the pathogen had been found in Manitoba soil earlier, but not detected in growing plants until last summer).
The pathogen continues to spread. With clubroot marked as a danger to Canada’s high value canola industry, money and research attention is being diverted to try to find more answers for farmers dealing with this disease. †