Clubroot is a soil-born root pathogen - Plasmodiophora brassicae. This pathogen is classified as a "Protist" because it has all characteristics of plants, fungi, and protozoans. Clubroot generally targets plants of the cabbage family (Brassicaceae) including mustard, bok choy, turnip, arugula, sprouts, broccoli, and radishes, even canola. First reported in the mid-70s, clubroot is not new in Alberta and since 2018 has been found in over 42 municipalities
The name ‘Clubroot’ comes from its peculiar appearance of many swollen roots that are irregular or club-shaped or a secondary taproot.
Due to the long lifecycle and easy transference of Clubroot, prevention is key. Managing land that has been infected is a long, challenging, and costly process.
How It’s Spread
Clubroot is not transferred through seeds into new fields, but through infected transplants or improperly decomposed compost, contaminated soil on equipment, and even the digestive tracts of livestock. Other ways that clubroot can spread are through soil moving in water or wind, hay, straw, and greenfeed for livestock.
It has been found that most new infestations begin at the entrance to fields which shows equipment could be the main cause of new infestations.
Periods of drought may seem to slow down Clubroot for a short amount of time, but the spores will become infective when there are heavy rains and high soil moisture. Be wary of greenfeed, hay and straw from areas with high water tables with lots of standing water in the fields.
Symptoms of Clubroot
It can be difficult to notice any signs or symptoms of clubroot infections, as the target spot is the roots. Above-ground symptoms are stunted growth, premature ripening, wilting, or yellowing of leaves.
The infection leads to swelling and distortion of the roots of the infected plants. This swelling is mainly caused due to water retention on the root depriving the plant of the necessary water and nutrients to survive.
P. brassicae is a long-lasting pathogen and can survive in the earth through spores for up to 20 years. While it is recommended to avoid planting any members of the brassica family for a minimum of 5-7 years, strict canola crop rotation can minimize the spread.
The half-life is 4 years for spores without a host, decreasing the viability of the infection. This doesn’t mean just crops, it also includes volunteer canola and cruciferous weeds as well.
An ounce of prevention is worth a pound of cure they say, and they are right. Some prevention techniques may sound laborious, but it is much easier and cheaper to prevent clubroot than manage it in the long run.
The best ways to prevent clubroot are
- Strict long crop rotation schedules
- Biosecurity and cleaning procedures
- Restrict movement on fields
- Using clubroot-resistant seeds
- Minimizing the use of hay and straw from suspicious areas
- Direct seeding and soil conservation practices
- Avoiding the use of common seeds
- Regular and thorough checks and samples of fields
Treatment and Management
While there is no treatment or cure for clubroot, proper management can minimize the impact on the current contaminated fields, and prevent further contamination in clean fields.
The best ways to manage clubroot are:
- Using clubroot-resistant seeds
- Controlling volunteer canola and cruciferous weeds from fields, approaches, and entrances
- Sanitation procedures of machinery and equipment - knocking the soil off machinery and cleaning with a 2% bleach mixture
- Limit all vehicles and equipment on contaminated fields
- Seed grass near the entrances to fields to remove soil from the tires of equipment and vehicles
- Establish new entrances to fields on the opposite side
The government of Alberta has a Clubroot Management Committee that will help support, provide training and education, and will evaluate and assess the spread of clubroot throughout Alberta.
At Strongfield, we are the soil experts and know how to help you strategize the prevention and contamination of clubroot and other contaminants in your field. Contact us today to prevent clubroot and other contaminants on your farm.