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How to Manage Pests
UC Pest Management Guidelines
Dry Beans
Southern
Blight
Pathogen: Sclerotium
rolfsii
(Reviewed 8/07,
updated 12/08)
In this Guideline:
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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.
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.
Rotation to nonhosts such as corn or small grains
for at least 2 years reduces inoculum. Burying plant refuse helps destroy
sclerotia.
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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
Acknowledgment for contributions to Diseases (Late-season decline):
J. Deelo, Plant Sciences, UC Davis
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