How to Manage Pests
UC Pest Management Guidelines
Corky Root Rot
Pathogen: Pyrenochaeta lycopersici
(Reviewed 12/13, updated 12/13)
In this Guideline:
Infected roots of plants with corky root rot are distinctly corky. Extensive brown lesions, often arranged in bands with lengthwise cracking of the cortex, develop on the larger roots. The tips of infected older roots are pinched off. Small feeder roots may be completely decayed. Infected plants are stunted and slow-growing. Branches on mature plants may die back from the tips.
Comments on the Disease
The fungus survives for long periods as microsclerotia. Potential alternate hosts include cucurbits, peppers, safflower, and solanaceous weeds such as on nightshades. Corky root is generally a problem in early plantings under cool conditions. Disease development is optimal at 60° to 68°F (15.5–20°C). Corky root usually does not kill plants, but may reduce yields.
Cultural practices, or soil fumigation on fields with a history of corky root rot, will help to minimize problems from this disease.
Organically Acceptable Methods
Cultural control is acceptable in an organically certified crop.
In fields with a history of corky root rot, a preplant treatment with metam sodium may reduce disease in a subsequent tomato crop.
UC IPM Pest Management Guidelines: Tomato
R. M. Davis, Plant Pathology, UC Davis