Southern Blight in Vegetable Gardens: White Rubbery Soil Fungus

Identifying the Pathogen

Small white, rubbery irregular pieces in garden soil near wilting tomatoes and zucchini indicate Southern blight (Sclerotium rolfsii). This fungus attacks at the soil line, girdling stems and causing rapid crown rot. White mycelial fans on stems and mustard-seed-sized tan sclerotia (survival spores) on the soil surface confirm diagnosis.

Immediate Actions

• Remove and destroy infected plants—do not compost.
• Excavate surrounding soil (6–8 inches deep) to reduce inoculum.

Protective Treatment for Remaining Plants

Drench healthy plants with chlorothalonil (Daconil): 2 oz per gallon water, 1 cup per plant base. Repeat every 14 days. This creates a protective barrier against fungal advance.

Long-Term Management

• Rotate to non-hosts (corn, grasses) for 2–3 years.
• Solarize soil in summer (clear plastic, 4–6 weeks).
• Improve drainage; avoid deep planting.
• Use raised beds with fresh soil if recurrence persists.

Sclerotia survive years, so prevention and rotation are essential.