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How to Manage Pests

UC Pest Management Guidelines


The white mycelium and sclerotia of the southern blight pathogen.

Dry Beans

Southern Blight

Pathogen: Sclerotium rolfsii

(Reviewed 8/07, updated 12/08)

In this Guideline:


SYMPTOMS AND SIGNS

Initial symptoms of southern blight include a yellowing of the foliage with slight darkening of the stem just above the soil line. Lesions on the stem at or near the soil line develop rapidly, girdling the stem and result in a sudden and permanent wilt of the plant. The fungus grows downward in the stem and root, rotting the cortical tissue. White mats of mycelium develop on the stem and in adjacent soil. In a few days, tan to brown spherical sclerotia (small dormant structures) about 0.06 inch (1.5 mm) in diameter appear on the mycelial mat. The abundant sclerotia are a good diagnostic feature of this disease.

COMMENTS ON THE DISEASE

High temperatures (above 85°F or 29°C) favor the disease. The fungus attacks a wide range of plants and survives for long periods in the soil as sclerotia. Southern blight is usually a minor disease of beans in California.

MANAGEMENT

Rotation to nonhosts such as corn or small grains for at least 2 years reduces inoculum. Burying plant refuse helps destroy sclerotia.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446
Diseases
R. M. Davis, Plant Pathology, UC Davis
C. A. Frate, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Abiotic Disorders:
A. E. Hall, Botany and Plant Sciences, UC Riverside
Acknowledgment for contributions to Diseases/Abiotic Disorders:
S. R. Temple, Plant Sciences, UC Davis
Acknowledgment for contributions to Diseases (viruses):
R. L. Gilbertson, Plant Pathology, UC Davis

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