Sclerotinia Frequently Asked Questions

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  When Should I be scouting for sclerotinia? The importance of the checklist.
Sclerotinia control decisions must be made before visible symptoms occur in the crop. Disease Forecasting for Sclerotinia can be a valuable tool for making these control decisions. The checklist should be completed when the crop is in the first flowering stage so that if control is needed it can happen at about the 25-30% bloom stage of the crop. First flower can be identified when 75% of the crop has three flowers on the main branch. In argentine canola 10% bloom is when there are 10 flowers on the main branch, 20% has 14-16 flowers on the main branch, and 30% has 20 flowers on the main branch. 25-30 % flowering can happen in 4-8 days from first flowering.

What weather conditions should I be concerned about?
If the conditions before and during flowering are damp and cool (15-25 degrees C) you may want to consider a fungicide treatment to protect your crop. If the weather during flowering is supposed to be dry, you may not be at as great a risk.

What causes the infection?
Sclerotia germinating in the canola or in fields adjacent to the canola crop produce spores and release them into the air. These spores infect the canola petals that are still attached and then use them as a food source for germination when they drop and get trapped in the leaf axils. The infection can then spread from the petal to the to the canola plant at the leaf axil. The infected branch may then die or ripen prematurely and shatter before the healthy crop is mature. There can also be plant-to-plant infection following lodging as infected plants contact healthy plants and the healthy plants and spread the disease. This infection doesn’t require spores or petals and the loss from this infection can be substantial.

Control Considerations
Control decisions are essentially based on environmental conditions and on the yield potential of your crop. If the environmental conditions favor the disease and you are expecting a high yield, you may want to consider control. Control should happen when the most flowers are open at once. This ensures that when the flowers start to fall, most of them are covered with fungicide.

Disease Forecasting for Sclerotinia (Contains The Checklist)
Disease Cycle-North Dakota State University
Canola Council of Canada Site (Has pictures)

Prepared by Karla Bergstrom, Ag-Info Centre, Alberta Agriculture and Rural Development

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This information published to the web on July 15, 2003.
Last Reviewed/Revised on April 22, 2008.