How to Manage Pests

UC Pest Management Guidelines

Dry Beans

Black Root Rot

Pathogen: Thielaviopsis basicola

(Reviewed 8/07, updated 8/07)

In this Guideline:


This disease occurs on blackeyes as well as on other dry bean types. Brown to black necrotic tissue develops on the below ground stems and roots. Fissures often develop in necrotic cortex tissue. Using a compound microscope the fungus can be identified in diseased tissue by the production of dark chlamydospores.


The fungus survives over a year in soil as chlamydospores. In blackeyes, Thielaviopsis basicola appears to be active on affected roots throughout the growing season.


Long-term crop rotation to nonsusceptible crops such as grasses may help to reduce soil inoculum. Avoiding excess irrigation or long drought stress may help.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446


C. A. Frate (emeritus), UC Cooperative Extension, Tulare County
P. Gepts, Plant Sciences, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

Acknowledgment for contributions to Diseases:
A. E. Hall (emeritus), Botany and Plant Sciences, UC Riverside
R. M. Davis (emeritus), Plant Pathology, UC Davis
R. L. Gilbertson, Plant Pathology, UC Davis
S. R. Temple (emeritus), Plant Sciences, UC Davis

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