Erysiphe cruciferarum

Fungal Disease

Powdery mildew, caused by the fungus Erysiphe cruciferarum, is a common disease affecting cruciferous crops like Brussels sprouts, swedes, and cabbages. It produces a white, powdery mould on leaf surfaces, spreading through wind-borne spores. The disease thrives in warm, dry conditions and can persist until crop maturity.

Key Points

• Cause:

  • Caused by Erysiphe cruciferarum (syn. E. polygoni).
  • Infects crucifer crops and cruciferous weeds.
  • Different strains affect specific crucifers.
  • Survives on infected plants or crop debris as chasmothecia.

• Favourable Conditions:

  • Warm, dry weather with low rainfall.
  • Reduced relative humidity.
  • Stressed plants are more susceptible.

• Symptoms:

  • Small white patches on both leaf surfaces.
  • Patches merge, covering leaves with a white powdery mass.
  • Leaves turn yellow, then necrotic.
  • Soft rot pathogens may invade affected areas.

• Effect of Temperature:

  • Disease development is slower at 14/10°C (day/night).
  • More severe at 22/17°C.
  • Germ tube growth peaks at 15–20°C.
  • Conidia survival decreases above 30°C.

Understanding the conditions that promote powdery mildew can help in managing its spread and protecting crucifer crops.