Common Scab of Potatoes

Common scab of potatoes is caused by a soil- and seed-borne bacterium, Streptomyces scabies, which is distributed worldwide. Infection causes tubers to have a scab-like surface lesion ("surface scab") which results in lower tuber quality. In severe infections, lesions are dark pits that can be as deep as a quarter inch ("pitted scab"). Streptomyces scabies can also attack other root crops, as well as the fleshy roots of weeds. It has been reported on beet, turnip, rutabaga, radish, carrot, salsify, and parsnip.