Spraying to prevent sclerotinia stem rot has started in Manitoba and many canola fields across the Prairies are coming into the spray window — 20% to 50% bloom. With good moisture and high humidity, growers with canola at early flower should use the checklist below to assess their sclerotinia stem rot risk. Fields scoring 40 or higher could benefit from fungicide, depending on canola price, yield outlook and fungicide cost.
When scouting for apothecia, the tiny mushroom-like structures that release infectious ascospores, keep two things in mind:
1) Make sure what you see are apothecia. They are tan or honey-coloured, 5 to 15 mm across, and tops are cupped like a golf tee. They will be growing from sclerotia in the soil or decaying canola. See the photo at the top.
2) When scouting for apothecia, check low spots in cereals that were in canola the previous year. If low spots are still water-logged, look in areas that have been wet but not saturated.
While flooded areas may kill sclerotia, many areas of the field will have prime conditions for sclerotinia stem rot infection. For more information on sclerotinia scouting, download our Canola Disease Scouting & Risk Assessment Card.