Remove all plant debris after harvest. Chemicals are not available for home garden use. The fungus Ceratocystis fimbriata causes black rot. Infected fleshy storage roots develop a firm, black, dry rot. Lesions enlarge throughout storage.
Black cankers form on the underground parts of the stem.
The fungus is usually introduced through the use of infected seed potatoes. It survives in crop debris in the soil. Sweet potatoes should not be planted in the same field more than once every third or fourth year. It is critically important for transplants to be cut at least 1 inch above the soil line, to exclude infected underground portions of the stem. Remove all plant debris after harvest.