Powdery scab

Symptoms

- Powdery scab is a fungal blemish disease of potatoes, which first shows as small raised pimples beneath the skin. As they develop, the skin breaks open to expose a dark brown powdery mass of cystosori or spore balls. Lesions are usually shallow depressions surrounded by raised torn edges of ruptured periderm. The dark spore balls under the skin can give the scab a dark margin.