Growers have more choice when it comes to clubroot resistant varieties as they make their seed selections for 2016. Some new varieties (with resistance traits discovered through grower-funded research) do show improved performance in the presence of new pathotypes, such as 5x.
However, at least 10 new pathotypes have been discovered in fields in central Alberta. While varieties with improved resistance to 5x may provide a benefit, this resistance may not work on all new pathotypes. Infection from the other virulent pathotypes could still occur.
That is why crop rotation remains important in fields where clubroot has infected canola plants. If clubroot symptoms have been observed in a field planted to a resistant variety, the responsible option is to not grow canola (any variety) for at least three years. This will help to preserve and protect new resistance genetics becoming available.
In fields that have produced two or more clubroot-resistant canola crops, longer rotation may be required to keep spore levels down to prevent significant losses. Next time canola is produced on those fields, consider rotating to a canola variety with improved resistance to 5x pathotype. This will help keep inoculum levels low and reduce selection pressure on the pathogen, making the resistance durable for longer.
In fringe areas where clubroot is present or nearby but no noticeable levels of infection have been found, consider any variety with some source of clubroot resistance in combination with prevention measures of equipment sanitation, host weed management and minimal tillage.