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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 varieties with genetic resistance, growers are encouraged to employ an integrated blackleg management strategy, including pre-harvest scouting for the disease, crop rotations and growing and rotating resistant varieties.

Integrated Blackleg Management Strategy

The following best practices should make up a grower’s integrated blackleg management strategy:

  • Blackleg pathogens overwinter on infected residue. Maintain a break between canola crops to allow time for crop residue to decompose – a minimum break of two to three years is recommended.
  • Scout canola fields regularly for blackleg symptoms and incidence to help determine the effectiveness of your blackleg management plan. See below for scouting tips.
  • 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.
  • During non-canola years, control volunteer canola and other Brassica weeds (e.g. stinkweed, shepherd’s purse, wild mustard and flixweed) to prevent blackleg build up in the field.

Pre-harvest Scouting

Although symptoms of blackleg appear throughout the season, the optimal time to scout for the disease is just before swathing (around 60% seed colour change).

To scout for blackleg, pull up at least 50 plants in a w-pattern through the field and clip at the base of the stem/top of the 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.

Blackleg Disease Severity Scale

Visit to learn more about blackleg management.

Managing disease pressures is just one of the 5 Simple Tips to keep your crops market ready. Working together, we can keep blackleg at bay and protect Canada’s reputation as a trusted supplier of high-quality canola.