Southern Blight (Sclerotium rolfsii): Sanitation, Solarization & Professional Treatment

Southern blight (also called southern wilt, stem rot, root rot), caused by Sclerotium rolfsii, attacks vegetables and ornamentals at or below the soil line in warm, moist summer conditions. White fungal mycelia and tan, mustard-seed-sized sclerotia at the stem base are diagnostic. Effective fungicides are restricted to commercial applicators; home gardeners must rely on cultural controls.

Symptoms

• Lower leaf yellowing, wilting, sudden plant collapse.
• White, fan-like mycelia on stem base and surrounding soil.
• Tan, round sclerotia (1–2 mm) on mycelia/debris—survival structures.
• Usually fatal.

Home Gardener Management

1. Sanitation (Primary)

• Remove soil from tools/shoes before moving between beds.
• Quarantine new plants 2–3 weeks in isolated bed.
• Destroy infected plants + surrounding soil + mulch/debris (bag/landfill/burn).
• Do not transplant nearby plants.

2. Soil Solarization (Warm Climates)

• Clear plastic on moist, tilled soil; bury edges.
• Top 2" must reach 122°F (50°C) to kill sclerotia.
• Effective in South; marginal in North (insufficient heat).

3. Professional Treatment (If Justified)

• Licensed applicators can use PCNB, tebuconazole, flutolanil, azoxystrobin (labels vary).
• Cost/benefit for home garden usually low—cultural controls preferred.

Key Reality

Sclerotium rolfsii survives years as sclerotia. Once established, it's a permanent resident. The gardener who sanitizes obsessively, solarizes annually in warm zones, and destroys outbreaks immediately keeps losses minimal. The one who ignores the white fans at the stem base loses bed after bed.