Prairie Crop Disease Monitoring Network (note the PCDMN Blog is no longer active): End-of-season assessment of blackleg of canola (PCDMN)

The spring and summer of 2023 was challenging for Prairie producers who experienced very dry conditions, especially under dryland production. Although this limited disease issues, the drought stress had a very significant negative impact on stand establishment, crop growth, and yield. However, some Prairie regions did receive moisture during the course of the summer and in these regions field crop diseases may be more of a concern.

Blackleg is one of the key diseases faced by Prairie canola producers and has largely been kept in check with the use of resistant varieties and crop rotation. However, over the past 10-20 years there have been concerns regarding observed shifts in blackleg pathogen virulence in response to the major gene resistance used in a number of varieties.

Changes in virulence patterns emphasize the critical need to stay on top of this disease; producers and crop scouts can play a critical role by scouting fields to monitor blackleg and detect any unexpected increases in disease levels on resistant varieties. For blackleg a critical time for scouting is later in the season to assess the prevalence, severity and impact of this disease issue.

When assessing blackleg incidence and severity, it is critical to correctly identify symptoms of blackleg and differentiate these from normal or premature canola crop ripening due to a range of abiotic and biotic factors. Recent Prairie research has shown limited responses to in-crop fungicide when resistant varieties are grown, and especially where this resistance is still highly effective.