Clubroot first appeared in Alberta in home gardens in the 1970s. In 2003, the disease was found in canola in 12 fields in Sturgeon County, northwest of Edmonton. From that time, a number of surveys have been conducted to monitor this disease. To date, over 6000 canola and vegetable fields have been surveyed, and clubroot has been confirmed in at least 830 fields in the province. Maps showing the affected areas and the spread of the disease over the years have been uploaded to the Alberta Agriculture website.
“Clubroot is an endemic disease, certainly in central Alberta,” says Dr. Ron Howard, plant pathology research scientist with Alberta Agriculture and Rural Development. “The disease is spreading by a variety of mechanisms and management is difficult. The number of new cases in 2011 (265 fields), represents the biggest single year increase in clubroot confirmed fields since 2003. The abundant rainfall we received last year was no doubt a contributing factor that favoured infection and disease development. Weather conditions have a huge effect on this disease, so in years, such as last year, where conditions are very wet, the incidence of the disease increases.”
Clubroot is a significant economic threat to the canola industry and was included as a declared pest under the Agricultural Pests Act in 2007. The disease is very difficult to control once it becomes established in a field. It decreases yield in canola and also poses a risk to mustard and cole crop vegetables in the province.
Clubroot management strategies include:
- removing soil and crop debris from equipment and machinery moving out of infested fields
- using direct seeding or minimum-tillage cropping methods, which reduces the movement of soil during tillage operations and reduces stirring the soil and the spread of the disease
- using long rotations between successive crops of canola to allow the pathogen population to decline in the interval
- avoiding spreading straw, hay, greenfeed, silage crops harvested from clubroot infested fields onto clean fields because of earth tag which can carry the disease
- NOT spreading manure from cattle fed with clubroot infested crops or forages on non-infested fields, as resting spores can survive passage through the gut of cattle
- NOT using common, untreated seed harvested from clubroot infested fields because of the possibility of dust and earth tag that may contain clubroot spores, and certainly dirty seed should be avoided
- regularly scouting canola, mustard and vegetable fields to discern the situation in the field and ensure that the disease isn’t spreading
“The advent of clubroot-resistant hybrids represents a major step forward in clubroot management,” says Howard. “The six products available seem to be standing up fairly well in clubroot infested areas. These varieties, while not completely resistant to clubroot, are not overwhelmed by the disease and yield is not reduced. It is very important to realize that even though a resistant variety is used, crop rotations of three years or more are still necessary to help slow the build-up of this disease in infested fields.”
Research is ongoing. Early on, there was very limited information on how to manage the disease in canola. Control strategies from vegetable growers were not that directly transferable. This prompted a whole line of research to look at disease management practices and to help understand the biology of the disease in canola. In 2009, the Clubroot Risk Mitigation Initiative was created using about $4 million in Growing Forward funding. This collaborative research has focused on pathology, breeding and disease management.
“An integrated approach is needed to manage this disease, including good stewardship of the resistant varieties of canola that are available,” says Howard.
Additional information on clubroot, including AgriFax and factsheets, is available on Alberta’s website at
www.agriculture.alberta.ca by typing clubroot into the search field.