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Powdery mildew
Erysiphe spp.
Fungal diseaseMedium impact
A fungal disease producing a white powdery coating on leaf surfaces. Thrives in warm dry conditions with high humidity, and is particularly common in late summer. Rarely kills plants but significantly reduces vigour and harvest quality.
Currently in peak season - extra vigilance worthwhile.
Key facts
- Type
- Fungal disease
- Active season
- Jul - Oct
- Peak season
- Aug - Sep
- Vulnerable stages
- Growing · Harvesting
- Spread rate
- moderate
- If confirmed
- Act soon
Signs & symptoms
- -white or grey powdery patches on upper leaf surfaces
- -older lower leaves typically affected first
- -leaves yellowing or dying back beneath the coating
- -distorted or stunted new growth in severe cases
Management
Do now
- -Remove and bin badly affected leaves - do not compost
- -Improve airflow around plants by removing crowded growth
- -Avoid water stress - plants under drought are more susceptible
Prevention
- -Choose mildew-resistant varieties where available
- -Space plants at recommended distances to allow airflow
Further reading
- -Unlike downy mildew, powdery mildew spores spread by wind and actually favour warm dry conditions - it does not need wet foliage to infect
- -The same plant can suffer both drought stress and powdery mildew simultaneously
- -Powdery mildew rarely kills established plants but significantly shortens their productive life