Information on Carrot -- Soft Rot (Core Soft Rot), An Online Guide to Plant Disease Control, Oregon State University

Pacific Northwest 1998 An Online Guide to Plant Disease Control

Carrot (Daucus carota) -- Soft Rot (Core Soft Rot)

Cause: Erwinia carotovora subsp. carotovora, a bacterium. Bacteria survive in decaying refuse and enter the root principally through cultivation wounds, harvest bruises, freezing injury, and insect openings. After infection, high humidity is essential for progress of the disease. When soft rot occurs in the field, it usually follows a period of water logging in low areas following excessive rain or irrigation. Carrots, parsnips, potatoes, onions, crucifers, and celery are only a few of the many plants attacked.

Symptoms: A soft decay of the fleshy root tissue takes on a watery or slimy consistency as the rot progresses. Rotted tissues keep their natural color until they completely decay. In the field, tops of rotted carrots turn yellow and wilt as roots break down.

Cultural control:

For the earliest and latest seedings of carrots, avoid fields subject to a high water table during wet conditions.
Harvest carefully, particularly during warm weather.
Carrots harvested for immediate sale when soil temperatures are high should be washed and cooled promptly and rinsed with clean, chlorinated water before being placed in a refrigerated holding area.
Harvest crops intended for long-term storage after soil and air temperatures are lower. Keep storage as close as possible to 30 to 32^oF and 85 to 90% relative humidity.
Thoroughly clean and disinfect bins between storage seasons.

References:
Segall, RH. and Dow, AT. 1973. Effects of bacterial contamination and refrigerated storage on bacterial soft rots of carrots. Plant Disease Reporter 57:896-899.

Content edited by: Cynthia M. Ocamb on January 1, 2010

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