As clubroot is becoming more prevalent in Strathcona County, making the choice to use sustainable agricultural practices such as extending crop rotations, cleaning your equipment and using clubroot resistant canola varieties can help protect your cropland now and in the future.

Infested fields experience economic losses through the reduction of crop yields and seed quality. The disease is long-lived and can spread easily by infested soil carried primarily by field equipment. Prevention and management are the best tools as there are not many control options available once a field has been infected with clubroot.

What is clubroot?

Clubroot is caused by a microscopic soil-borne pathogen called Plasmodiophora brassicae that infects the roots of cruciferous plants such as:

• Canola and mustard crops
• Vegetable crops such as broccoli, cauliflower, brussel sprouts, cabbage, radish, kohlrabi, turnip and kale
• Weeds including wild mustard, stink weed and sheperd's purse

Clubroot spores move readily with any soil movement. The primary mode of transportation is field-to-field by contaminated equipment. It can also move through wind, water, soil erosion and animals. Dust or earth tags from infested fields can contaminate seeds, hay and straw.

Galls appear on the roots of the infected plants, ranging from tiny nodules to large club-shaped growths that may involve most of the root system. At first the galls are firm and white but become soft and greyish-brown as they mature and decay. Severely infected roots cannot absorb enough water and nutrients to properly nourish stems and leaves which results in stunting and wilting. At the end of the season, the galls break down into the soil releasing millions of new spores and the cycle continues.

Symptoms of clubroot vary throughout the growing season. Early infection at the seedling stage can result in wilting, stunting and yellowing of plants in the late rosette to early podding stage. Infection that occurs at a later crop development will cause plants to ripen prematurely and the seeds will shrivel.

Clubroot spores can live in the soil for up to 20 years. The half-life of these spores is about four years - after four years, if there is no host available, half of the spores will no longer be viable. Tight canola rotations (1 in 2 years) allow for quick development of the disease once it has been introduced in the soil. Long rotations (1 in 4) are recommended to prevent disease development and to protect the breakdown of resistant traits in clubroot resistant canola varieties.

Research has shown that fields with 100% infestation will have a yield reduction of 50%. A field with a lower rate (10 - 20%) of infection will have a lower rate of loss (5 - 10%). The plants may not appear to be affected by the disease; however, if the disease is not managed and allowed to spread, the infection rate will increase rapidly. Within only a few canola seasons the spores will multiply quickly and the disease will become much more difficult to control. The loss to crop production will become very evident.

Frequently Asked Questions

Restrictions recently approved by Strathcona County's Agricultural Service Board

Restrictions placed on clubroot fields through management plans and notices will include:

• Landowner/producer shall not plant canola including clubroot-resistant varieties or other susceptible crops for the following two years (1 in 3 crop rotation)
• Non-resistant varieties shall not be planted for the following three years (1 in 4 year crop rotation)
• Proper sanitation of field equipment and vehicles will be mandatory

Best Management Practices and Recommendations for Landowners, Producers and Industry

The following management practices are recommended in the Alberta Clubroot Management Plan developed by the Alberta Clubroot Management Committee and the provincial government:

• Use clubroot resistant varieties in areas known to have clubroot. Resistant varieties should be rotated to prevent the breakdown of resistant traits.
• Use long crop rotations (three or more years) between canola crops to reduce disease severity and reduce other crop diseases. Fields with confirmed clubroot should use resistant varieties and follow crop rotation practices of one canola crop every four years.
• Control volunteer canola and weeds to prevent spore production on host plants.
• Clean and sanitize equipment, vehicles and machinery to restrict the movement of contaminated soil.
• Implement soil conservation practices including minimizing tillage and using direct seeding as spores can move with wind and soil erosion.
• Minimize traffic in fields, especially during wet conditions. Discourage recreational vehicles from crossing land with signage, fencing and gates.
• Fields with light infestations in the entrance can create a new vehicle approach at another edge of the field.
• Scout fields regularly and identify causes of wilting, stunting, yellowing and premature ripening.
• Avoid using straw, hay, manure and silage from areas known or suspected of clubroot. Clubroot spores may survive through the digestive tracts of livestock.
• Avoid common untreated seed as earth tags may carry clubroot spores.
• Work your most infected field last.

Further information: