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Growing a clubroot-resistant variety is an important step in clubroot management for farms with clubroot, for farms in a county, district or municipality with clubroot and for farms adjacent to an area with clubroot.
The number of farms that fall into one of these three categories increases every year and took a big leap in 2017. Five new counties were added to Alberta’s clubroot map in 2017. They are Big Lakes, Brazeau, Lac La Biche, Paintearth and Wainwright. Saskatchewan confirmed a number of cases in Districts 9A and 9B. Farmers in these districts as well as Districts 6B, 7B and 8B will want to consider CR varieties. Saskatchewan districts map. As of 2016, Manitoba had symptoms observed in four municipalities (shown in red on this map).
With so many new areas that need to deploy CR varieties, farmers may want to book seed early.
Is there a yield drag with CR varieties? For many seed companies, the CR trait is in some of their highest-yielding varieties. Even if there is no clubroot, the CR trait does not necessarily mean a yield trade-off. One option is to use canolaperformancetrials.ca and other data sources to compare yields for all CR varieties.
When the same CR variety is grown in a field with heavy clubroot pressure and in a field with no clubroot pressure, it will tend to yield more in the field without clubroot. That’s because the energy required to fight off clubroot can reduce the overall yield potential. Keep that in mind when evaluating yield for these varieties under CR pressure situations, noting that a non-CR variety grown in that same situation would have yielded much less.
What else can you do to manage clubroot? Genetic resistance is just one step. Extending rotations to provide a two-year break between canola crops will also reduce clubroot spore load.
Further reading:
Biosecurity and clubroot: How it spreads
New CCC clubroot publication “Understanding clubroot resistance”
clubroot.ca