Given the ubiquity of sclerotinia, it’s surprising that there are still some commonly held myths about how this disease behaves and how best to treat it.
For instance, there are some who still believe that if sclerotinia pressure was low last year, it’ll be low again this year. Sadly, that’s not true because that’s not how the sclerotinia life cycle works.
If you want to stay on top of sclerotinia, it’s important to understand what conditions favour disease outbreak, how the disease behaves, and what control strategies work best so that you can protect the yield potential and quality of your canola crop.
Here are some things to think about when it comes to effectively managing sclerotinia.
Disease inoculum is always present. Sclerotia are underground fungal storage bodies and can survive in soil for at least three years, sometimes up to five. They remain dormant until conditions are favourable, at which point some of them will germinate to form spore-producing apothecia (tiny mushroom-like structures). Those that don’t germinate continue on resting underground.
Since canola is widely grown across the Prairies, sclerotia are present in almost every field, just waiting for the right conditions. So when disease pressure is low one year, that doesn’t necessarily mean it will be low the next. To be safe, you should really just plan ahead for the possible presence, or risk of sclerotinia every year.
Moisture is the main risk factor. While this is true, moisture can come in many forms. For example, a good rain before or at flowering is an obvious risk factor for scleortinia. But also risky is a crop stand dense enough to create a warm, humid microclimate under the canopy. This is a perfect environment for disease outbreak, even without a rain event. Be mindful that high humidity alone and heavy morning dews are risk factors as well.
Don’t wait to see symptoms. By the time you see visible symptoms of sclerotinia, such as lesions on stems or leaves, then it’s already too late to prevent yield loss. Even if you spray the second you see those symptoms, it’s still too late. This is why preventative fungicide application for scleortinia is critical to protect your crop.
How do you know when to spray? If conditions are right for a sclerotinia outbreak, and if your crop looks like it’ll have a great yield, an application of Proline® fungicide at around 20 to 50 per cent bloom is going to protect that yield.
This timing is key since yield loss from sclerotinia is roughly half of the infection rate in the field, meaning that if 20 per cent of your field was infected, then yield loss would be around 10 per cent. Left untreated, the crop could, potentially, be lost altogether. Don’t take that chance!