Managing Onion White Rot in Large-Scale Production

No Quick Fix for White Rot

Onion white rot (Sclerotium cepivorum) is a persistent soil-borne disease. For a 30-acre operation producing 900 tonnes annually, finding infected patches across multiple paddocks is serious. Hydrogen peroxide foliar drenches are ineffective—the fungus resides in the soil, not on foliage.

Recommended Actions

• Remove and destroy infected plants immediately to reduce inoculum.
• Solarize affected soil by covering with clear plastic for 4–6 weeks during the hottest part of summer to kill sclerotia.
• Rotate crops—avoid alliums in infected paddocks for at least 5–7 years. Use clean ground for new plantings.
• Practice strict sanitation: clean equipment between fields to prevent spreading sclerotia.

There are no curative treatments once plants are infected. Prevention through rotation, sanitation, and solarization is the only reliable strategy for commercial-scale onion production.