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Onion white rot
Stromatinia cepivora
Fungal diseaseHigh impact
A highly persistent soil-borne fungal disease that attacks the roots and base of alliums. Sclerotia (resting bodies) survive in soil for 20+ years, making rotation largely ineffective once a plot is infected. Prevention is far more important than cure.
Outside typical active season.
Key facts
- Type
- Fungal disease
- Affects
- Garlic · Spring-onion
- Active season
- Mar - Jul
- Peak season
- Apr - May
- Vulnerable stages
- Growing · Harvesting
- Spread rate
- slow
- If confirmed
- Act now
Signs & symptoms
- -yellowing and dying back of leaves starting from the tips
- -white fluffy fungal growth at the base of the bulb or stem
- -roots rotting away from the base upward
- -small black sclerotia (like poppy seeds) visible in the white growth
- -plants pulling out easily with little root resistance
Management
Do now
- -Remove and bin infected plants including surrounding soil - do not compost
- -Do not move soil from affected areas to other parts of the garden
- -Mark the affected area and avoid growing alliums there indefinitely
Prevention
- -Buy only certified disease-free planting stock
- -Never introduce soil from other gardens or allotments without quarantine
- -If white rot is suspected, treat the area as permanently compromised for alliums
Further reading
- -Sclerotia can survive in soil for over 20 years - crop rotation does not resolve the problem once established
- -The disease is most active in cool, moist soil conditions