Blackleg in canola can cause yield and quality losses, impact profitability and may create a market risk. To help manage the disease and maintain the effectiveness of genetic resistant varieties, producers are encouraged to employ an integrated blackleg management strategy, including pre-harvest scouting for the disease. By examining the cross section of clipped stems, a grower can discover the severity of infection, estimate the impact on yield and determine the effectiveness of their management plan.
Prior to swathing, visit the field to look for signs of blackleg. Pull up at least 50 plants in a w-pattern through the field, starting at the field edge, and clip at the base of the stem/top of root to look for blackened tissue.
Any black discolouration seen in the cross section can be compared to the disease severity scale (below). The scale rates plants from 0 (no discolouration) to 5 (completely discoloured), and with each step on the rating scale there is a reduction in yield.
The following best practices should make up a grower’s integrated blackleg management strategy:
- Maintain a break between canola crops to allow time for crop residue to decompose. If blackleg becomes established, a minimum break of two to three years is recommended.
- Scout canola fields regularly for blackleg symptoms and prevalence to help determine the effectiveness of your blackleg management plan.
- Plant only canola varieties rated R (resistant) or MR (moderately resistant) to blackleg. Rotate varieties to bring a mix of blackleg resistance genes and sources to the field over time.
- Consider applying a fungicide from the cotyledon to 4-leaf stage if in a higher risk situation for the disease.
- Control volunteer canola and other Brassica weeds (stinkweed, shepherd’s purse, wild mustard, flixweed) to prevent blackleg build up during non-canola years.
Working together, we can keep blackleg at bay and protect Canada’s reputation as a trusted supplier of high-quality canola. Visit blackleg.ca to learn more.