How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Charcoal rot affects all cucurbits. Crown leaves of infected plants turn yellow and wither. The vines may wilt and die, depending on the extent of infection. A green, water-soaked lesion forms on the stem near the ground level and may produce amber gumming. The lesion may extend several centimeters up the vine; as it dries the color changes to tan.

COMMENTS ON THE DISEASE

Macrophomina phaseoli is a soilborne fungus, occurring in most soils in the Central Valley. The fungus is relatively tolerant of high temperatures and dry soils. Disease incidence is favored by plant water stress and high temperatures. The disease is most commonly observed on plants that have been attacked by nematodes or root rot fungi and are suffering from water stress. This fungus has a wide host range and is a common problem on beans.

MANAGEMENT

Maintain optimal soil moisture to avoid plant stress. Rotate cucurbits with a small grain crop. There are no chemicals or resistant cucurbit varieties available for use in controlling this disease.

PUBLICATION

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445
Diseases
R. M. Davis, Plant Pathology, UC Davis
T. A. Turini, UC Cooperative Extension, Imperial County
B. J. Aegerter, UC Cooperative Extension, San Joaquin County
W. D. Gubler, Plant Pathology, UC Davis
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier

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