Assessing Sclerotinia Risk in Canola

Early May 2014 seeded canola is now flowering, and later May seeded crops are not too far behind. With the widespread rainfall in Manitoba over the Canada Day weekend, soils are moist to saturated and temperatures are favorable for sclerotinia infection and development.

MAFRI currently does not produce sclerotinia risk maps like we do for Fusarium Head Blight, as we do not have a proven and consistent model to forecast sclerotinia risk.   Alternatively, there is a newly posted risk assessment calculator for sclerotinia spray decisions and economic imapct available at

We have the inoculum as we grow multiple sclerotinia susceptible crop (canola, soybean, sunflower, dry bean, etc.), but risk and disease development is dependent on a combination of inoculum as well as day/night temperature, precipitation, crop canopy and soil moisture.

 Scout and monitor your fields, disease development risk increases (and need for fungicide) if you have the following conditions:

  • Ground is damp to wet and,
  • Canopy is moderately closed to closed (i.e. you cannot see the ground through the leaves), and
  • Canopy is still damp to wet when walking through the field at 10am (i.e. your pants are wet), and
  • Field is at 20 – 50% flowering 


Flowers open  = % flowering?

Find the main stem on the canola plant to assess flowering

  • 10% flowering = 10 open flowers 
  • 20% flowering = 14-16 open flowers 
  • 30% flowering = 20 open flowers, some small pods 
  • 50% flowering = >20 open flowers, small pods and a few well formed

Conditions can change throughout flowering.  If the canopy is wet now at 6 leaf stage, but your plant stand is thinner and the canopy is open and dry at 20% flower you may not feel that you need to spray, but if you are at 10% flowering now, the canopy is thick and the ground is wet, you may want spray.

The MAFRD Guide to Field Protection for Disease Control can be found at

 Prepared by:  Anastasia Kubinec – MAFRI Oilseed Crop Specialist  

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