Blackleg in 2026: Why August is the Critical for Protecting Canola Yield
Canola crops have been flowering for a few weeks or are moving towards the flowering stage. August 2026 is shaping up as one of the most important months for disease management. While most growers are familiar with crown canker blackleg early in the season, upper canopy infection (UCI) has been highlighted as a higher risk this year.
Earlier sowing, improved genetics and longer flowering periods have shifted many crops into their most susceptible growth stage just as the blackleg spores reach peak release from last year's canola stubble.
Most years we will decide that not applying a fungicide is the right approach financially and Agronomically. This season is shaping up differently. Blackleg is already prevalent in a lot of canola crops.
Why August Matters
Dr Steve Marcroft, through the GRDC National Canola Pathology Program, has shown that the timing of flowering is one of the biggest drivers of upper canopy blackleg.
Canola beginning to flower during late July and early August is exposed to the highest levels of airborne blackleg spores. Cold, wet conditions during this period favour infection of the upper canopy.
Unlike crown canker, these infections occur well above the ground, restricting moisture movement into developing pods and reducing grain fill. Yield losses commonly range from 0–20%, but losses of up to 20–40% have been recorded in severe seasons where pod infection is extensive.
What Makes 2026 Different?
Many regions now have:
- More canola in the rotation
- Greater amounts of infected canola stubble
- Earlier sowing dates
- Earlier flowering crops
- Blackleg overcoming some of the most common canola resistance genes
Every one of these factors increases disease pressure.
Know When Your Crop is at Risk
The highest risk crops generally have several factors working together:
✓ Flowering during late July or early August
✓ High rainfall or frequent rainfall events
✓ Last year's canola stubble nearby
✓ Susceptible or moderately susceptible varieties
✓ Intensive canola rotations
Lower risk crops include those flowering from mid to late August, when spore pressure and the opportunity for disease to cause yield loss begin to decline.
Where crops are considered high risk, fungicides applied around early flowering, (approximately 20–30% bloom) can reduce upper canopy infection while also contributing to sclerotinia management where conditions favour both diseases.
Ensure your crop is protected during August.
10–30% bloom is the supported decision window, with the best timing depending on crop phenology, weather, and disease risk.
Discuss fungicide options and timing with your Agronomist. Product choice should always follow the current Australian label and resistance management guidelines.
Take Home Messages
August is decision month.
If your crop is flowering during August:
- Assess blackleg risk before flowering.
- Consider nearby stubble and seasonal conditions.
- Know the resistance package of your variety.
- Don't assume early-season blackleg protection extends into flowering.
- Time fungicide applications to protect the upper canopy if disease risk justifies the investment.
- Use integrated disease management to preserve valuable fungicide chemistry.
Download the Upper Canopy Blackleg Management App to help with decisions https://www.dpird.wa.gov.au/online-tools/uci-blacklegcm/
The most profitable blackleg management is rarely about one product - it is about combining variety selection, rotation, stubble management, crop monitoring and well-timed fungicide applications to protect yield potential.