Canola Alternaria Black Spot

Alternaria black spot is a fungal disease affecting canola in Western Canada. Canola can be at risk for infection during all stages of growth generally starting with seedlings, but increases with plant growth. Extensive spreading can increase green seed count, chlorophyll content, reduce oil content, and 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.

Disease Life Cycle

What To Look For

Pod Infection

Severe 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