A test of canola stubble can determine (1) if blackleg is present and (2) what race of blackleg it is. This can help farmers and agronomists make proper use of the blackleg resistance-gene (R-gene) classification system when making seed decisions. The Canola Encyclopedia has the full list of blackleg labs.
Check with labs to see what they need for samples.
If a field has increasing incidence of blackleg, that is a sign that the pathogen population has shifted to a race or races that will overcome the dominant R-gene in the canola variety last grown on that field. By identifying the blackleg race, growers can then choose a variety with resistance to that race.
The Canola Encyclopedia has more on blackleg identification and management.