Oklahoma State University



Canola Diseases

Aster Yellow

  • Caused by a micoplasma like organism.
  • Plants remain in the vegetative state during the entire growing season.
  • Flower structures remain green and fail to ripen.
  • Spread from plant to plant in the fall by the six-spotted leafhopper.
  • There is no practical means of control, but generally less than 2 percent of plants are infected.


Aster Yellows Questions and Answers


Blackleg (Leptosphaeria maculans)

Blackleg SW Okeene (pdf)

Tools to Minimize the Potential for Blackleg (pdf)

EPP-7671 Blackleg disease of Canola
(this will redirect you to the fact sheets section of this web site).

  • Survives in infected seed, canola stubble.
  • Serious infection caused by spores released from infested stubble.
  • Introduced into new areas with infected seed.
  • Leaf; light green and circular to irregular in shape. Spots become paper-thin and buff-colored with age and contain numerous pycnidia.
  • Cankers from in spring after flowering and have lost their potential for compensatory growth.


Scleroninia Stem Rot (Sclerotinia sclerotoirum)

  • Most severe in warm wet conditions during flowering.
  • Soybeans, peanuts, sunflowers are hosts.
  • First symptom is prematurely ripened plants.
  • Stems are bleached and tend to shred.
  • Hard black structures known as sclerotia appear inside the stems near the soil line.
  • Symptoms of stem rot appear about 10 to 14 days after infection.


Powdery Mildew (Erysiphe cruciferarum)

  • White dusty growth on aboveground plant parts.
  • Favored by
    • Moderate temperature
    • High humidity
    • Excessive N fertilizer
    • Excessive canopy density
  • Should remain a minor disease in Oklahoma


Alternaria Black Spot (Alternaria spp.)

  • Yields are affected when pods are split or early infection kills plants.
  • Black, brown, or gray spots on leaves, stems and pods.
  • Over winters in infested residue and seed.
  • Control achieved by sowing clean, disease-free seed or crop rotation.


White Rust (Albugo candiada)

  • White to cream colored masses appear on the underside of leaves. Raised green blisters form that turn white during wet weather.
  • Major symptoms is swollen, twisted and distorted inflorescences called "stagheads" that become brown, hard and dry as they mature.
  • Yield losses of 20% have been recorded.

Document Actions