Canola plants that exhibit brown superficial symptoms at ground level likely have Fusarium root rot, which produces tan brown lesions with concentric markings.
Another possibility affecting canola roots at adult stages is Brown Girdling Root Rot (BGRR), which is more of an issue in Polish canola.
Symptoms of BGRR are rusty brown lesions on the canola tap root, which may girdle and pinch off the root if severe. These diseases can be much higher in tight canola rotations.
What to Look For
Early stage root rot Brown Girdling root rot
Late stage root rot Stages of root rot
Prevention
There are many different strategies you can use to help prevent the spread of Brown Girdling Root Rot:
- Follow good agronomic practices
- Alternate canola with cereal crops by allowing 3-4 years in between
- Seed shallow to reduce severity
- Control cruciferous weeds and volunteers within all crops
- Avoid seeding canola on clover sod or canola stubble on newly broken land