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No silver bullet for international disease

Scientists from around the globe met in Edmonton to discuss the latest on clubroot

University of Alberta researcher Victor Manoli tours International Clubroot Workshop delegates through his research work at Alberta’s Crop 
Diversification Centre North. Manoli has infected these plants with clubroot spores to enable future study.

The world’s top canola researchers and agronomists met in Edmonton in early August to talk about their work on the pathogen that’s lowering canola yields throughout Alberta and spreading to the rest of the Prairies. While researchers at the International Clubroot Workshop discussed the scientific research underway, farmer delegates were disappointed to hear there is still no “magic bullet” to conquer clubroot, and researchers don’t see one coming in the near future. As new strains of the clubroot pathogen overcome clubroot-resistant seed, Canadian farmers will be living with clubroot for the long haul.

Researchers are learning more about the pathogen, developing new clubroot-resistant seed varieties and finding better ways to measure the presence of clubroot. But for now, planting resistant seed, rotating crops to avoid planting canola within two years on the same field and sanitizing agricultural equipment that may carry clubroot spores are still the most effective tools farmers have to protect against infection.

Unfortunately, Bruce Gossen, Agriculture and Agri-Food Canada research scientist, told delegates, though long rotations and sanitization are effective, “growers won’t use them.” Farmers reliant on immediate cash returns from canola crops are reluctant to implement longer rotations — surveys have found that 10 to 15 per cent of farmers do not give their soil the recommended breaks from canola. As well, farmers find that fully sanitizing agricultural equipment to remove all clubroot spores is time consuming, which is especially problematic during busy seasons.

At Alberta’s CDC North, northeast of Edmonton, University of Alberta graduate student Brittany Hennig explains her research, using lime to suppress clubroot spores, to 
International Clubroot Workshop delegates. photo: Leeann Minogue

Researchers are assessing the potential of using soil amendments like lime and fumigation to lower the load of clubroot spores in infected soil. Gossen says liming “looks positive,” as a way to keep the load of clubroot spores low, but the costs of fumigation are too high for widespread use. “There’s not a lot that can be done on a large scale,” he said.

“This is not an easy problem to solve,” agreed conference attendee Carol Holt, farmer from Bashaw, Alta., and agronomist with Univar. “There are limited control measures and they can’t be easily applied.”

Clubroot has only recently affected North Dakota and the Peace River region of Alberta, but international delegates from countries including Japan, China, Poland, Sweden and Germany brought stories of their long history with clubroot, which also impacts other cruciferous crops such as broccoli and cabbage. “We think it’s just started, but we’re just the last to get it,” said conference delegate Wayne Truman, Saskatchewan farmer and SaskCanola board member.

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