You discover clubroot in a field: Tips

You’ve been diligent scouting for clubroot, or maybe you just accidentally stumbled upon some infected plants. However you found it, what should you do next?

John Guelly, a farmer at Westlock, Alberta, has first-hand clubroot experience. Guelly has wise words for those finding clubroot in their fields for the first time: “Blame is not a useful management tool for clubroot. The sooner you accept the situation and begin your own clubroot management plan, the better off you and your fields will be.”

Discovering clubroot in your fields is not the end of the world. Early detection and management changes will allow you to continue to grow canola with clubroot. Check out the to-do list below, then visit the clubroot.ca when you have time to dig into more detailed information.

Immediate action

1. Note the area and severity of infection:
   • Mark the affected area(s) with GPS and/or stakes. If you skip this step, you might not be able to locate infected areas next year.
   • Note the clubroot severity: are you finding a few smaller galls or are there large-sized galls on most roots?
2. Avoid driving through clubroot-infected areas (especially when soil is wet):
   • Cultivators, sprayers, trucks, quads, etc. can all move soil, and spores move where soil moves. 
   • Reducing soil movement from clubroot patches will reduce the spread of clubroot spores within and between fields.
3. Collect information from the field:
   • What is the crop rotation in that field?
   • What field did you come from during seeding? What field followed?
     • Seeding equipment will carry soil between fields and soil can contain spores. Knowing this can help you identify other infected fields.
   • If clubroot is present in a clubroot-resistant (CR) hybrid:
     • Record which hybrid.
     • Collect a large ziplock bag of galls and store them in the freezer.
     • Contact CCC agronomy specialist and clubroot lead, Autumn Barnes (barnesa@canolacouncil.org) for more information on pathotyping.
4. Hand-pick and destroy clubroot-infected canola plants:
   • One gall can produce billions of resting spores, so removing galls before they decompose will reduce future clubroot risk.
     • Mowing or spraying the affected area(s) does not remove galls or resting spores from the field.
   • Cut off the galled roots from their stems and put the galls in a heavy garbage bag.
     • Dispose of the bags in a landfill.
     • Using an incinerator is an option; however, the temperature may not be hot enough to kill the spores in a fresh, moist gall.
5. Increase scouting for clubroot:
   • How to identify clubroot.
   • Assume that if one of your fields has clubroot, they might all have it (likely at different levels).
   • Look for root galling in all canola fields.
   • Examine roots of canola volunteers and brassica weeds in non-canola fields.
6. Be open and honest about it:
   • Talk with an agronomist.
   • Inform the adjoining landowners(s).
   • Share biosecurity expectations with anyone working in or accessing the infected field(s).
   • Consider reporting the field to municipality staff, who participate in provincial disease surveys which track the spread of clubroot for research purposes.

Ongoing

1. Patch management:
   • Manage clubroot patches separately from the rest of the field to reduce spore concentration and prevent spores from spreading:
     • Note boundaries of the patch(es).
     • Remove and destroy galls.
     • Apply lime until soil pH reaches at least 7.2 (more on liming here)
     • Seed a sod-forming grass to anchor soil.
     • Control weeds in the patch.
     • Avoid travel through known clubroot patches.
   • When spores are reduced enough in the patch(es), break the sod and return the area to annual cropping with the rest of the field.
     • A PCR test detects the presence or absence of clubroot in the sample.
     • A qPCR test quantifies the number of spores per gram of the sample. 
2. Lengthen crop rotation:
   • A two-year break from clubroot hosts will reduce resting spores by around 90%.
   • Fields or patches with high spore concentrations will need more than a two-year break, as the remaining 10% of spores will still be high enough to cause disease. 
3. Reduce soil movement:
   • Minimize tillage in all fields.
   • Avoid travelling through clubroot-affected area(s), especially in wet conditions.
   • Knock soil off of equipment before leaving fields. Detailed sanitation tips here. 
4. Control volunteer canola and other brassica weeds:
   • Volunteer canola, stinkweed, flixweed, shepherd’s purse, and mustards are all susceptible to clubroot.
   • Early weed control is key to minimizing spore reproduction and clubroot risk.
5. Develop a clubroot management plan:
   • Include goals for scouting, stewarding CR hybrids, and biosecurity.
   • Visit clubroot.ca for more detailed information.