Should I Spray My Canola a Second Time for Sclerotinia?

Prepared by Holly Derksen, MAFRI Field Crop Pathologist

Probably not. We only see consistent results from a fungicide application to help control sclerotinia in canola when the application is made prior to the 50% bloom stage. Even if your canola has been flowering for a long period of time this year if your bloom stage is past 50% it is unlikely that you will see a benefit from a fungicide application at this stage.

Petals that are present in the later flowering stages may become infected with sclerotinia, but at this stage your canopy has filled in so when these petals fall they are landing in upper leaf axils. Infection of the stem in these upper portions is unlikely to have a big yield effect. However, at 20-30% bloom – that key timing for a sclerotinia fungicide application – petals that fall land on lower leaf axils and are more likely to cause infection on the main stem and potentially wipe out an entire plant. In any year, one well-timed fungicide application, at 20-30% bloom (but definitely prior to 50% bloom!), will provide the best economic return (assuming there is disease pressure).

For more information, check out Real Agriculture’s Canola School Episode on Sclerotinia Control – Assessing Bloom and Why 50% Bloom Can Be Too Late

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