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Spring and Winter Canola:
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| Author: | OMAFRA Staff |
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| Creation Date: | 01 March 2002 |
| Last Reviewed: | 01 March 2002 |
| Agronomy Guide > Pub 811: Spring and Winter Canola >White Mould (Sclerotinia Stem Rot) |
White mould is a canola disease that is sporadic within a region and varies greatly from year to year. This makes predicting disease potential or outbreaks very difficult. The disease is very destructive during periods of prolonged, wet weather. Losses of up to 50% can occur under ideal conditions.
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White mould is characterized by bleached stem lesions and hard black bodies (sclerotia) of white mould fungus inside the stems; it causes premature ripening of the plants.
Plate 144. White mould (Sclerotinia stem rot) causes white (bleached) stem lesions and hard black bodies in the stems.
Plate 145. White mould on seed. The black bodies of white mould are sometimes found in the seed at harvest.
The disease is often a problem when canola follows canola, white beans, soybeans or sunflowers. Infections that start on the dead blossoms spread to adjacent tissues, resulting in dead branches or dead plants. Plants may lodge. The rotted stems usually have a bleached appearance. Sclerotinia infections can be serious on canola if cool, wet weather occurs in the last 2 weeks of June and continues into early July when blossoming occurs.
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Use clean, certified seed and rotations of at least 4 years, including unaffected crops such as corn, wheat, barley or oats in fields with a history of Sclerotinia or white mould. During this rotation, it is necessary to avoid planting susceptible crops including mustard, sunflower, dry bean, soybean, field pea, lentil or garbanzo bean. At present, no resistant varieties exist. Keep fields clean of broad-leaved weeds since many are alternate hosts for this disease. Foliar fungicide treatments are effective but require scouting and precise timing. Refer to the OMAFRA Publication 812, Field Crop Protection Guide, for more information on recommended fungicide treatments. (Order OMAFRA Publication 812)
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