Sclerotinia Stem Rot In Canola

Sclerotinia stem rot is one of the most common diseases of canola on the Prairies. This pathogenic fungus can cause great loss when conditions are favourable. Conditions such as temperature, precipitation, and soil moisture will affect the risk of the disease and the rate of development. With the recent precipitation in the Prairies, farmers should take extra care when scouting for Sclerotinia. The infection is likely to occur if there is heavy moisture affecting canola two weeks before and continuing during flowering.

Is it worth it to spray?

Fungicide will reduce the severity of Sclerotinia, but it will not be eliminate it completely. Before applying fungicide, farmers should check the current moisture levels of the field as well as the yield potential of the crop. A saturated crop with high yield potential will probably provide a good return from applying fungicide. If weather conditions become hot and dry, the risk of Sclerotinia development is greatly reduced. Since moisture conditions are hard to predict, it could be risky to leave a high yielding crop unsprayed.

When should you spray?

Canola is at the greatest susceptibility to Sclerotinia when it is flowering. Spraying at the flowering stage will provide the greatest protection against infection. Specifically, fungicide should be applied when canola is between 20-50% bloom (starting 4-5 days after the first flower). Since Sclerotinia can only affect dead spores, the timing of spraying is important. It is important to monitor your crop throughout the entire 20-50% bloom range, as weather conditions can affect the presence of the infection.

Which conditions should I look for?

Scouting is especially important if:

  • The ground is damp
  • You cannot see the ground through the leaves of your crop (closed canopy)
  • The canopy is still wet at 10am
  • Canola is between 20-50% bloom
  • Moisture conditions increase

Have you found the incidence of Sclerotinia infection in canola to be higher this year?

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