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How to Manage Pests
UC Pest Management Guidelines
Dry Beans
Charcoal
Rot (Ashy Stem Blight)
Pathogen: Macrophomina
phaseolina
(Reviewed 8/07,
updated 12/08)
In this Guideline:
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Charcoal rot is most serious on common beans and then blackeyes; it
also occurs on limas. Symptoms may appear after the pathogen, which can be
soilborne, germinates and infects seedling stems near the soil line at the base
of developing cotyledons. The fungus produces black, sunken cankers that have a
sharp margins and often contain concentric rings. The plant's growing tip may
be killed or the stem broken where it is weakened by the canker. Infection may
continue into the hypocotyl and root region or the primary leaf petioles. Root
infection causes a brown to black necrosis. If plants are grown under dry land
conditions, young plants can be killed.
Infection of older seedlings and plants may cause stunting, leaf
chlorosis, premature defoliation, and plant death, especially during periods of
high temperature and particularly following drought stress. On older plants "charcoal
dust" often appears on
the surface of the stems and is diagnostic evidence for this disease. This
charcoal effect is caused by the production of small, black microsclerotia just
below the epidermis and in the vascular tissue. This symptom is also called
ashy stem blight.
The fungus is pathogenic on many crops including corn and sorghum,
and the disease tends to be worse on certain soils. Although the fungus is
capable of infecting plants at all stages of growth, severe disease primarily
occurs under conditions of drought stress and high temperatures, especially
when a late irrigation is applied.
Avoid drought stress especially during periods of high temperature.
A 3-year rotation with a cereal crop may help reduce soil
inoculum.
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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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