2025: Monitoring for Resistance Breakdown in the Clubroot Resistant Cultivars of Canola

In the ongoing annual clubroot survey in canola fields, a crucial research initiative was conducted in 21 counties of North Dakota. The survey revealed a breakdown of first-generation resistance to clubroot in resistant canola cultivars in Cavalier County for the second consecutive year (Table 1). The breakdown of cultivar resistance to clubroot is a significant threat to the canola crop. However, with the proper measures, such as practicing longer crop rotations (one in four years) in acidic soils, using multi-gene clubroot-resistant canola cultivars, and maintaining proper equipment sanitation in endemic areas, growers can play a crucial role in preventing the spread of clubroot. These measures have been proven effective, and we urge you, as key stakeholders, to implement them with confidence. A grower’s commitment to cleaning equipment thoroughly after working in a clubroot-infected field is critical, as the primary mechanism of spread between fields is the movement of infested soil on farm equipment.

Table 1: Level of clubroot damage observed in clubroot-resistant cultivars released by four different seed companies that are widely planted to manage clubroot in NE North Dakota.

*Clubroot resistant cultivars of canola were designated differently by respective industries.

Notice: Growers who are curious about the presence of clubroot/resting spores in their field(s) are encouraged to contact Dr. Venkat Chapara at the Langdon REC (701-256-2582), NDSU Cavalier County Extension Office (701-256-2560), or NDSU Extension (701-231-8363).

Figure 1: Severe galling of the roots was observed in the clubroot resistant varieties of canola.

Figure 2: Patch of clubroot infections in a canola field planted with a clubroot resistant variety.