WATCH: Managing Blackleg

Proper management of blackleg in canola is essential for minimizing disease severity and protecting crop yields.  
 
This article outlines proven management practices, including plant scouting, crop rotation, genetic resistance and fungicide use as discussed by Justine Cornelsen, Agronomic and Regulatory Services Manager with BrettYoung Seeds.

Introduction to Blackleg 

Blackleg is a longstanding disease affecting canola, primarily caused by the fungal species Leptosphaeria maculans. While multiple pathogens contribute to blackleg, Leptosphaeria maculans is the main source of yield loss. A combination of management strategies can effectively reduce severity and prevent the spread of this disease. 

Essential Management Practices for Blackleg 

1. Plant Scouting 

Plant scouting is considered the most important practice in blackleg management. 

• Inspect fields and plants: Go into the field and pull up canola plants.   
• Assess plants before or at harvest: Assess the plants for damage, typically done at harvest or just before harvest.   
• Examine for internal damage: Cut plants through the root tissue to evaluate the extent of damage.   
• Rate disease severity: Rate disease severity and estimate potential yield loss for the season.   

2. Crop Rotation 

Crop rotation is critical because blackleg is a stubble-borne disease that survives on old canola residue. 

• Reduce infection risk by residue breakdown: Once the residue decomposes, infection risk decreases.   
• Implement two-year crop breaks: Implement at least a two-year break from canola by rotating with other crops such as soybeans or wheat.   
• Lower pathogen pressure: This break reduces old residue and lowers pathogen pressure.   

3. Genetic Resistance and Genetic Rotation 

All canola hybrids in Canada must be resistant or moderately resistant to blackleg. 

• Adopt resistant hybrid varieties: Growers are already using resistant hybrids as part of their management.   
• Rotate major resistance genes: Rotate genetics as part of trait stewardship, using different major resistance genes.   
• Utilize diverse portfolio options: Within the BY (BrettYoung) portfolio there are multiple options to rotate genetics.   
• Match genetics to detected pathogens: Understanding the pathogen present at the field level and using varied genetic tools enhances management success.   

4. Fungicide Use 

Fungicide applications provide another important defense against blackleg. 

• Apply foliar sprays early in season: Most applications are foliar sprays applied early in the season, around the two-leaf stage.   
• Target infection window for impact: Early application during the infection window leads to a meaningful reduction in disease severity by fall.   
• Use seed treatment options: Newer options include fungicide seed treatments such as Sutro™, which protect young canola plants as they emerge through the cotyledon to two-leaf stage.   

Combining all these management practices, especially emphasizing crop rotation, is essential for effective blackleg control in canola crops. Consistent plant scouting, proper crop rotation intervals, use of genetic resistance and timely fungicide applications work together to minimize disease severity and protect yield. 

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