Clubroot is a serious disease of cruciferous crops that occurs worldwide. It is a major problem in commercial cole crops in Quebec, Ontario and British Columbia, and has been confirmed in a number of canola and cole crop fields in the Edmonton area.
The infestation near Edmonton has spread since the first infested canola field was confirmed in 2003. While clubroot occurs mainly on cole crops such as broccoli, brussels sprouts, cabbage, cauliflower, Chinese cabbage, kale, kohlrabi, radish, rutabaga and turnip, it can also infect black mustard and canola.
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“The fungus causes large galls to form on roots, which then restrict the transport of water and nutrients to above-ground plant parts,” said Murray Hartman, oilseed specialist with Alberta Agriculture.
“Wilting of plants and premature ripening are common symptoms. Prematurely ripened patches of clubroot could be mistaken for a sclerotinia infestation. In canola crops, the seed yield is severely reduced.”
The root galls release mobile spores that infect neighbouring plants. There is a resting spore stage that is extremely long lived, lasting up to decades. Soil transport is the main mechanism of disease spread.
To limit the disease, follow these tips:
- Sanitation is essential and producers are urged to clean dirt from all equipment, including tires, before leaving infected fields. Do not remove straw or bale straw from fields.
- Minimize soil erosion on infected fields.
- Do not seed canola on infected fields for five to seven years. Also, the following alternate hosts should not be seeded or transplanted: cole crops, red clover, orchardgrass and strawberries.
- Volunteer canola, weeds in the mustard family, dock and hoary cress must be controlled in following crops. Volunteer canola and winter annuals in the mustard family such as stinkweed, shepherd’s purse and flixweed, should be controlled in the early fall.
- There is evidence that liming acid fields, those with pH less than 6.0 to above 7.0, can reduce disease severity.
