Features Agronomy Diseases
Clubroot management plans implemented

Equipment sanitation is a key management practice. Photo by Bruce Barker.

Clubroot researchers are throwing a huge effort into understanding the disease, and while new clubroot-resistant canola varieties from Pioneer Hi-Bred give producers an option, canola growers are encouraged to understand the Clubroot Management Plans that have been implemented by the Saskatchewan and Alberta agricultural departments.

In Alberta, clubroot was declared a pest under the Agricultural Pests Act in April 2007. This means the owner or occupant of the land has the responsibility of taking measures to prevent the establishment of clubroot on the land, or destroy the pest on the land. Control measures for clubroot are specified in this management plan. It is important to understand that these control measures represent an acceptable standard that is to be applied in all municipalities across the province. Municipalities can enhance the standard within their own jurisdictions.

Saskatchewan followed in June 2009 when they declared clubroot a pest, with similar restrictions and management plans. Rural municipalities may choose to create a policy outlining the surveillance and management of clubroot at the municipal level, preferably with consideration of recommendations found in the Saskatchewan Clubroot Management Plan. “Our plan is focused on public awareness and education,” explains Faye Dokken, provincial specialist in plant disease with the Saskatchewan Ministry of Agriculture in Regina. “We want to help producers prevent the establishment of the disease.”

Murray Hartman, provincial oilseed specialist with Alberta Agriculture and Rural Development at Lacombe, Alberta, says the key to helping stop the spread of clubroot is to prevent the spread of the resting spores that are found in the soil. Resting spores are extremely long lived, with a half-life of about four years, yet being capable of surviving in soil for up to 20 years. The longevity of the resting spores is a key factor contributing to the seriousness of the disease, especially under tight canola rotations.

Growers, custom operators and all land users (including oil and gas industry and recreationalists) need to be vigilant and diligent in removing potentially contaminated soil from equipment prior to leaving fields, to prevent the introduction of clubroot to clean fields.
Although clubroot-resistant varieties are entering the Canadian market, resistance breakdown has been common in other parts of the world. Therefore, the effort to reduce the spread of clubroot spores on contaminated equipment should continue.

Best management practices
The Clubroot Management Plan developed in Alberta and Saskatchewan are similar, and focus on crop rotation and equipment sanitation. The following best management practices are taken from the Alberta Clubroot Management Plan. This plan is currently being revised to include the use of clubroot-resistant canola varieties.

1. Use long rotation breaks between canola crops. Although crop rotation will not prevent the introduction of clubroot to clean fields, it will restrict disease development within the field and probably avert a severe infestation of clubroot and other diseases such as blackleg. Canola growers in high risk situations (confirmed clubroot in the area) should follow traditional canola rotation recommendations (one canola crop every four years). Under very light infestations, a three-year rotation break from canola will keep the clubroot level very low. Under moderate to high infestations, the rotation break needs to be five years or more to reduce clubroot to low levels when using susceptible varieties.  If a resistant variety is used, a three-year rotation break will be acceptable.
2. Volunteer canola and cruciferous weeds must be controlled on infested fields to prevent more than three weeks of growth to avoid the production of new resting spores.
3. Practice good sanitation to restrict the movement of potentially contaminated soil. This approach will also help reduce the spread of other diseases, insects and weed seeds. The resting spores are most likely to spread via contaminated soil. Moderate to high infestations will leave high spore concentrations in soil on field machinery, thus sanitation is very important in these situations. All producers should follow the practice of cleaning soil and crop debris from field equipment before transport from all fields. Cleaning equipment involves knocking or scraping off soil lumps and sweeping off loose soil.
   For risk averse producers or for fields with heavy infestations, additional cleaning steps will decrease the risk of spread slightly, but these steps involve considerably more work and expense:
   • After removal of soil lumps, wash equipment with a power washer, preferably with hot water or steam.
   • Finish by misting equipment with a weak disinfectant (one to two percent active ingredient bleach solution). The use of a disinfectant without first removing soil is not recommended as soil inactivates most disinfectants. Dr. Ron Howard with Alberta Agriculture in Brooks is leading a project to compare the efficacy of various cleaning methods and disinfectants for removing clubroot spores on equipment.
   • Seed an area to grass near the field exit to clean off equipment more effectively.
4. Use direct seeding and other soil conservation practices to reduce erosion. Resting spores can also readily move in soil transported by wind or water erosion. Reducing the amount of tillage on any given field will reduce the spread of the organism within the field and to other fields.
5. Minimize traffic to and from fields.
6. In situations where fields are lightly infested only near the current access, create a new exit at another distant edge of the field if possible.
7. Scout canola fields regularly and carefully. Identify causes of wilting, stunting, yellowing and premature ripening: do not assume anything. Scouting should continue even with resistant varieties so that resistance breakdown can be identified as soon as possible.
8. Avoid the use of straw, hay or greenfeed, silage and manure from infested or suspicious areas. Clubroot spores may survive through the digestive tracts of livestock.
9. Avoid common untreated seed (including canola, cereals and pulses). Earth-tag on seed from infested fields could introduce resting spores to clean fields. The effect of current seed treatment fungicides on resting spore viability on seed is a current research project. There are no soil fungicides, foliar products or seed treatments registered for control of clubroot on canola in Canada. However there are several research projects looking at the efficacy of such products for clubroot in canola. The risk of spreading clubroot through contaminated seed or plant material is much less than through transporting contaminated soil on field equipment.
   The Canadian Association of Petroleum Producers has developed a set of best management practices designed to promote the development of effective and achievable procedures to minimize the spread of clubroot pathogen spores in areas in which susceptible crops are grown.