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This soil-borne canola disease is spreading. Strategies to control it are on the way. Still, growers are advised to be vigilant.
There’s good news and bad news for Alberta producers when it comes to clubroot in canola. The bad news is, a 2008 field survey found this destructive canola disease in 18 Alberta counties, six more than in 2007.
The good news is, a host of counter-measures by governments, canola growers and plant breeders are beginning to show progress.
“Clubroot continues to be a very serious disease from the standpoint of how it spreads and its longevity in the soil,” says Murray Hartman, Lacombe-based Oilseed Specialist with Alberta Agriculture and Rural Development.
Clubroot has been known in Europe for more than a century, mainly for its damaging impact to brassica crops like cabbage, broccoli and cauliflower. Clubroot, which can reduce canola yields by up to 50%, thrives under moist conditions and in acid soils. This disease is mainly spread by soil, in which clubroot spores are able to live for up to two decades, once introduced. Other methods of transmission are documented, but are not significant.
With no fungicides registered for use on canola for clubroot in Canada, and resistant varieties not yet commercially available, that leaves cultural practices as farmers’ most viable line of defence (see sidebar).
Alberta’s Clubroot Management Committee – representing governments, scientists, canola growers and the Canola Council – met in Lacombe this past October 16 to review the current clubroot situation. While results from the 2008 field survey were a clear concern, other news provided cause for optimism.
“Right now, the energy companies are doing a good job of keeping their equipment clean,” says Hartman, “though generally, farmers could be doing much better. There are also eight or nine clubroot management research projects that are currently underway or are about to begin. Researchers are making good progress on resistant varieties. Some clubroot-resistant canola seed could be available in 2009 or 2010.” |
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Clubroot in Canola. This destructive canola disease was found in 18 Alberta counties in 2008.
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6 steps to prevent or contain clubroot
Clubroot, while serious, is still not widespread in Alberta canola fields. To help keep it that way, producers are advised to follow these management recommendations.
1. Use long rotations, growing canola only every four years or more in the same field. Although this practice will not prevent the introduction of clubroot to clean fields, it will restrict disease development within the field and likely avert a severe infestation.
2. Practice good sanitation to restrict the movement of possibly contaminated material. (This will help reduce the spread of other diseases, weeds and insects, too.) Resting clubroot spores are most likely to spread via contaminated soil and infected canola plant parts. Producers should follow the practice of cleaning soil and crop debris from field equipment before entering or leaving all fields. The equipment cleaning procedure involves knocking or scraping off soil lumps and sweeping off loose soil.
For the more risk-averse producers, additional cleaning steps may provide some extra benefit, though they involve considerably more work and expense. After removing soil lumps, wash the equipment off with a power washer, preferably with hot water or steam. Finish by misting equipment with a weak disinfectant (1% to 2% household bleach solution).
3. Use direct seeding and other soil conservation practices to reduce erosion. Resting spores move readily in soil transported by wind or water erosion and by overland flow.
4. During the growing season, scout canola fields regularly and carefully. Identify causes of wilting, stunting, yellowing and premature ripening – do not assume anything.
5. Avoid the use of straw bales and manure from infested or suspicious areas. Clubroot spores are reported to survive through the digestive tracts of livestock.
6. Avoid common untreated seed (including canola, cereals and pulses). The risk of spreading clubroot by contaminated seed or straw is much less than by the transportation of contaminated field equipment. Nonetheless, Earth-tag on seed from infested fields could introduce resting spores to clean fields. Certain seed treatment fungicides may control spores on contaminated seed, but this observation needs further research to confirm its validity.
Source: Alberta Agriculture and Rural Development |
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