Managing clubroot continues to be a challenge for canola growers, especially as more pathotypes are identified across Western Canada. While the growing list can feel overwhelming, the real focus remains on the few that are most widespread and impactful.
Ongoing efforts to standardize resistance labeling, combined with clear best management practices, are giving growers the information they need to make confident decisions and better protect their fields from this evolving disease.
Diversity at the field level
Of the 55 pathotypes identified in Canada, 35 can overcome some of the resistant canola hybrids in the marketplace. And as alarming as that may sound, many of those pathotypes have only been identified once or a couple times.
The most predominant pathotypes in Western Canada continue to be 3A, 3D and 3H, which make up 57% of the pathotypes identified through grower field surveying. Pathotypes 5L, 8A and 9E round up the other relevant pathotypes. So what do we make of the other 49 pathotypes discovered?
BrettYoung’s Agronomic and Regulatory Services Manager, Justine Cornelsen, said when selecting a canola hybrid for the season, growers need to focus on the select few predominant pathotypes and not get overwhelmed with the diversity of clubroot pathotypes out there.
“We do see new relevant pathotypes emerging but for the most part a lot of the pathotypes discovered are one-offs, they’re never seen again,” says Cornelsen. “And from that comes a lot of marketing around resistance labelling to pathotypes that really aren’t relevant.”
Saskatchewan and Manitoba continue to have under 100 fields per province with confirmed clubroot infections, where Alberta has over 4,000 confirmed fields with the disease.
Labelling initiatives
The Canola Council of Canada (CCC) is leading a cross-industry initiative to standardize a product labelling system that will help growers determine and compare resistant hybrids between seed companies. The labelling system’s focus is on the three predominant pathotypes (3A, 3D & 3H) and will look to add others once they become more established.
Rigorous field and indoor screening of hybrids has always been a part of the BrettYoung Clubroot DefendR® designation. Through this new initiative and the use of a consistent clubroot inoculum source, there is now much more confidence in labelling hybrids for their resistance against specific pathotypes.
Stacking major clubroot resistance genes into a single hybrid is an important factor in how effective and durable resistance is in clubroot-resistant hybrids. This approach has proven to be very effective and targets a variety of relevant clubroot pathotypes.
Clubroot Best Management Practices
Clubroot is to be managed using an integrated pest management approach and not by relying on a single practice to keep the disease at bay. Crop scouting and identifying clubroot patches in the field will help determine what other best management practices (BMPs) need to be adopted.
Key Management Practices for Clubroot
- Minimize soil movement: Reduce transfer of infected soil between fields to help manage spore spread.
- Control host weeds and volunteers: Eliminate canola volunteers and host weeds to minimize sources of infection.
- Practice crop rotation: Rotate crops to lower spore loads and decrease selection pressure on hybrids.
- Scout for disease patches: Regularly assess fields to identify and manage early signs of clubroot.
- Use resistant hybrids: Choose clubroot-resistant hybrids to protect future crop potential.
- Adopt patch management: Limit susceptible host plants in high spore load zones with targeted management techniques.
“Selecting hybrids for clubroot resistance durability can only be achieved when other best management practices, mainly crop rotation, are followed to help alleviate the selection pressure,” she said.
FAQ
What are the predominant clubroot pathotypes in Western Canada?
The predominant clubroot pathotypes in Western Canada are 3A, 3D, and 3H, which account for 57% of the pathotypes identified through grower field surveying.
Why should growers focus on predominant pathotypes instead of all identified pathotypes?
Growers should focus on the predominant pathotypes because many of the others have only been identified once or a few times and often do not appear again. These rare pathotypes are considered far less relevant for guiding resistance decisions. The predominant pathotypes are the ones most consistently found in Western Canadian fields, so they present the greatest risk and should be the primary drivers of hybrid selection.
What is the Canola Council of Canada doing to help growers with clubroot resistance?
The Canola Council of Canada is leading an initiative to standardize a product labelling system that focuses on the three predominant pathotypes, helping growers determine and compare resistant hybrids between seed companies.
What are some best management practices for clubroot in canola fields?
Best management practices for clubroot include crop scouting, minimizing soil movement, controlling host weeds and volunteer canola, and practicing effective crop rotation to reduce spore loads.
Why is stacking major clubroot resistance genes into a single hybrid important?
Stacking major clubroot resistance genes into a single hybrid is important because it increases the effectiveness and durability of resistance against a variety of relevant clubroot pathotypes.
What is recommended for fields wanting to grow canola in the future?
For fields wanting to grow canola in the future, using a clubroot-resistant hybrid and employing patch management techniques to limit susceptible host plants in high spore load areas is recommended.
