By: Cory Jacob, PAg., Regional Crops Specialist, Watrous
Clubroot is a soil-borne disease of canola and other crops in the Brassicaceae (mustard) family including mustard, camelina and related weed species. The clubroot pathogen (Plasmodiophora brassicae) infects plants through the roots leading to swollen deformed roots, which reduce the plants’ ability to take up nutrients and water from the soil, ultimately leading to premature death of the infected plant. Clubroot is a serious disease of canola and should not be taken lightly. However, with the use of good agronomy and the latest in plant breeding technology the disease is manageable.
Clubroot galls were identified on the roots of canola plants this past summer in Saskatchewan crop districts 9A and 9B, which is North Central and Northwest Saskatchewan. The identification of clubroot in Saskatchewan should not surprise anyone since the pathogen can be moved in soil and the disease is already present in Alberta and Manitoba. Couple that with the canola acreage in Saskatchewan and tight crop rotations, it was only a matter of time before the disease was found in our province and now we have to deal with it. The specific locations of where clubroot has been identified in those crop districts are not being released publicly due to confidentiality restrictions and the nature of the disease. It is highly unlikely that clubroot is only present in those identified fields in those crop districts as the spores of the pathogen can be present in a field at low levels without showing symptoms on the plants. With the likelihood of clubroot being present in other fields in crop districts 9A and 9B and potentially other areas in the province, growers need to be utilizing proactive management strategies and scouting their fields to detect the disease early.
Clubroot is best managed by preventing the introduction of the pathogen to a field. There are management practices that you can use to manage clubroot, whether you have discovered it in a field, you farm in an area where it has been detected or you are just generally concerned about the disease:
- Plant susceptible crops, including clubroot-resistant canola varieties, no more than once every four years. If you farm in crop districts 9A or 9B, a switch to clubroot-resistant canola varieties is recommended and the implementation of a four-year crop rotation.
- Weeds in the Brassicaceae (mustard) family are clubroot hosts, so control of them will help to keep spore numbers down. Weeds in this family include all mustards, volunteer canola, flixweed, shepherd’s purse, stinkweed and more.
Minimize traffic to and from fields and practice good sanitation to restrict the movement of soil from the contaminated field to other fields or other parts of the field. Sanitation includes removing crop debris and soil, washing with a power washer using hot water and misting with two per cent bleach.
- If the clubroot infestation is located at the field entrance or a patch within the field, consider seeding that area to a perennial grass and creating a new access point as far as possible from the infected area. When possible, create a separate exit far from the field entrance to reduce the movement of the pathogen inoculum out of an infected field.
- Use direct seeding and other soil conservation practiced to reduce erosion and soil movement.
To monitor for the presence of clubroot in a field, scouting of both susceptible and resistance canola varieties is recommended for clubroot symptoms, which are galls on the roots. Scouting should be focused to field entrances and areas of the field that showing symptoms of wilting, yellowing, stunting and premature ripening. DNA-based soil testing can used to detect the pathogen at lower levels than what will cause symptoms in the field. A number of private labs offer this test for a fee. Before sampling, contact the lab about the proper sampling location and depth as this will influence the ability to detect the pathogen in the field.
In Saskatchewan, clubroot is a regulated pest. Under The Pest Control Act, rural municipalities (RMs) have the authority to undertake prevention and enforcement measures related to the spread and control of clubroot. The provincial government does not have authority under The Pest Control Act.
When clubroot is identified in the province through the Ministry of Agriculture’s annual canola disease surveys, the information is kept confidential. Only general information is released publicly to inform producers in the region that clubroot has been found to allow producers to manage appropriately. Ministry specialists will also provide support to producers and agronomists to develop farm-specific clubroot management plans. Specialists will only disclose the location of the infected fields to the RM offices when the RM has a clubroot-specific bylaw enacted.