Alternaria black spot is a fungal disease that affects canola in Western Canada. 

What are the Risks?

Canola can be at risk for infection during all stages of growth. Generally, infection starts with seedlings and will increase with plant growth.

Extensive spreading can:

  • Increase green seed count
  • Increase chlorophyll content
  • Reduce oil content
  • Cause premature pod shattering.

Although the Brassica napus canola variety is less susceptible than Brassica rapa, it can also be affected by Alternaria black spot.

What to Look For

Black Spot Pod Infection          Black Spot Leaf Lesion             Black Spot Stem infection

      Pod Infection                                              Leaf lesion                                             Stem infection


Although Alternaria black spot is not as potentially destructive as other crop diseases, it is still important to practice proper management strategies:

  • Use least susceptible varieties
  • Plant clean, high germination pedigreed seed
  • Use registered seed treatments
  • Timely fungicide application
  • Swath early to limit pod shattering

Related Links

Disease of Oilseed crops - Alternaria black spot

Canola Encyclopedia Alternaria black spot