Common scab is caused by a bacterium.
Common scab is caused by the bacterium Streptomyces scabiei. On the tuber (potato, black radish) form brown corky patches several millimeters in size. The roots may also be affected. The bacteria attack the tubers through the lenticels. The spots do not affect edibility or taste. Underneath the spots the potatoes is healthy. The spots can easily be cut away by peeling the potatoes.
Contamination occurs from the soil and through infected seed potatoes.
Where to find
Control
The damage often only becomes visible during harvest. By then it is too late to reverse the infestation.
Prevention
There are potato varieties that are less susceptible to common scab.
