Relatively low levels of sclerotinia infection can be found in most areas except in heavy and late maturing crops in northwest Saskatchewan where disease pressure is high due to frequent rains through the flowering period. Higher amounts of alternaria are occurring in B. juncea and B. rapa in western Saskatchewan and in B. napus fields in eastern Manitoba. In eastern Manitoba, more blackleg is appearing.
Scouting and identifying disease(s) present can be a valuable tool for assessing this year’s production practices and preparing for next years. Here’s what to look for with blackleg: symptoms showing up at this stage of the season are greyish lesions on the stem with the black picnidia spots, and also basal lesions (cankers) — which are the most serious. Basal lesions can’t really be properly identified until you cut through the base of the stem and look for blackened infection. This infection will eventually grow through the stem, cutting off nutrient flow. If you see plants drying up, cut a few open at the base of the stem with clippers to check. With sclerotinia look for white lesions or fuzzy rot on the main stem or on branches. Sometimes the plant may look healthy at the base, but there will be dead branches. Infected stems and branches will have white-grey tissue (not green) and will often start to shred apart easily. Click here to see photos of sclerotinia and blackleg infection.