These three questions will help canola farmers and agronomists assess the sclerotinia stem rot risk in their areas.
The decision to apply a fungicide to prevent sclerotinia stem rot may be generalized by answering these four questions: (1) Have environmental conditions prior to flowering been wet enough for apothecia development and survival? (2) Is the canola crop canopy dense and is yield potential high? (3) Does the weather forecast predict precipitation and/or humidity during the flowering period? (4) Is the pathogen present in sufficient quantities?
Once petals drop and start to decay, infection proceeds very quickly with lesions being visible in as little as 24 hours.
Timing and coverage are keys. For most fungicides, the recommended window for application falls between 20 and 50 per cent bloom, with optimum timing typically around 30 per cent bloom.
Hot, dry weather reduces infection rates and the progression of sclerotinia within the plant. The disease risk is limited when current conditions are dry, max daily temps are 30°C or more, and forecast is for this to continue for seven to 14 days. Hot weather can also increase flower and pod abortion, which could reduce […]
Canola cultivars are available with improved tolerance to sclerotinia stem rot. This reduced severity of sclerotinia stem rot is effective but may not match the same level of control as a fungicide application. Therefore under high risk of disease development applying a fungicide to these cultivars may still be necessary.
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