A clean routine continues to be the best defence against clubroot.
While the canola disease has yet to be found outside of Alberta, many producers think its spread is only a matter of time.
It has been confirmed in counties along the southeastern border with Saskatchewan and is suspected and confirmed one county away from the border east of Edmonton.
Clubroot fungus infections have been a problem for generations in commercial brassica crops in Europe, infecting rapeseed, cabbage and broccoli. In Canada, it can reduce canola yields by more than 50 percent, thriving in moist, acidic soil conditions.
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Murray Hartman of Alberta Agriculture said clubroot spores can remain viable in the soil for more than two decades, waiting for a chemical signal from the roots of susceptible crops that a host is present and ready to be infected.
No registered fungicides are available in Canada to control clubroot, but new, resistant canola varieties might eventually make prairie fields an inhospitable place the spores.
Pioneer Hybrid released its 45H29 variety earlier this year, with limited supplies available this season.
Kevin Auch of the Alberta Canola Producer’s Commission said producers were surprised that researchers were able to develop the resistant crop only six years after clubroot was discovered near Edmonton. They are now enthusiastic about a future where the infection is controlled.
However, Auch said the disease is far from defeated.
Resistant genetics are only one tool, he added, and farmers need to use a variety of methods to control the disease, such as eliminating spread from field to field.
Clubroot patterns of infection form around field access points where contaminated soil is tracked into fields by farm equipment, oilfield machinery and pick-up trucks operated by farmers and surveyors.
Hartman said avoiding the spread begins with establishing who is in the field and why.
The oil and gas industry generally cleans equipment between fields, he added, but farmers could do better.
John Mayko of the Canola Council of Canada said clean equipment and vehicles are key.
“You can start by knocking off the big, loose stuff, use (compressed) air, high pressure water to get at the rest. And we are recommending a weak bleach solution to finish,” he said.
“I know many producers want to avoid the bleach due to its corrosive properties, especially with all the electronics and hydraulics on modern equipment, but it’s the best science we have on the subject right now.”
Alberta provincial plant pathologist Ron Howard is leading a project to test alternative biocide cleaning products at a research facility in Brooks, Alta.
One such product is Virkon, a veterinary bactericide and fungicide. The potassium monopersulfate product is used to clean and disinfect agricultural buildings, veterinary hospitals and food processing plants.
Mayko said the prairie provinces, industry organizations and crop genetic and pesticide companies are investing in future control methods, but developing a cleaning routine on the farm remains the best approach.
“We will still have to deal with issues of spread from farm equipment sold at auction sales and trucked into new locations, but that is just one more thing that farmers have control over,” he said.
Agrologists say another challenge has been maintaining crop rotations that help avoid the development of large clubroot populations.
The snow, canola and snow rotation that prairie agrologists describe as a being used extensively led to several disease problems, including clubroot.
Limited profitability from most crops during much of the past decade encouraged continuous planting of canola.
Hartman said limiting production to once every four or five years in a field will not prevent the spread of clubroot, but it will limit the population and the level of damage that clubroot inflicts on a crop.
How to identify clubroot
Clubroot masquerades as more common canola diseases such as blackleg, sclerotinia or fusarium wilt. Hybridization nodules are uncommon but are easily confused with galls. So how do you tell the difference?
Clubroot and its galls:
- Interiors spongy and marbled.
- Irregular in shape.
- Tops vary in appearance, depending on growth stage.
- Early year infection causes wilting and stunted growth.
- At podding, crop ripens prematurely. Seeds are shrivelled and plants show poor yield as galls tie up nutrients and
prevent water from being transported, giving the appearance of drought damage.
- Galls are found at six to eight weeks after primary infection, so problems are not usually encountered until later in the season.
- Problems generally found in patches, rather than in larger, whole field infections.
Canola hybridization nodules:
- Round, small shape with firm texture.
- Located at the roots’ nodes.
- Consistent appearance, similar to other healthy root tissue.
Prevent clubroot spread through equipment sanitation
A clubroot sanitation program involves three steps:
1. Remove soil and plant debris from equipment by scraping or knocking off clumps.
2. Clean residual soil and debris from surfaces by pressure washing, steaming or compressed air.
3. Apply a disinfectant mist to the clean surfaces (1-2% active ingredient bleach solution).
The most likely equipment to become contaminated with clubroot spores is:
- Tillage equipment (cultivators, discers, rippers, harrows).
- Fertilizer and pesticide applicators.
- Seeders (air seeders, drills, discers).
- Tractors, grain trucks, pickups, cars and ATVs.
- Swathers and combines.
- Grain handling equipment (augers, dryers).
- Forage harvesting equipment.
- Miscellaneous equipment used for soil sampling, trenching, clearing brush, etc.
This equipment may be difficult to clean because of its size, shape or complexity:
- Air seeders
- Combines
- Multi-wheeled tractors
- Large grain trucks
- Grain augers, dryers
- Forage harvesting equipment
Sometimes, air is best:
- Electronics may not be compatible with water, detergents or disinfectants. Clean these items with compressed air instead.
- Check with the manufacturer to ensure that the cleaning and disinfecting procedures you plan to use will not damage sensitive equipment.
Source: Alberta Agriculture, Canola Council of Canada
