potato powdery scab

Potato powdery scab Common name Potato powdery scab Causal agent Potato powdery scab is caused by fungi in the genus Spongospora. It is common in potatoes, but tomato species can also be infected. Besides powdery scab, it also causes gall formation on the roots. Scientific name Spongospora subterranea Symptoms & Signs Potato powdery scab is characterized by purplish-brown, raised pustules that transform into brown lesions. The lesions rupture the tuber periderm, giving it a scab-like appearance. The pustules also contain spores that take part in the spread of disease. It also shows gall formation on the root, which turns brown as it grows. Transmission The disease spreads through spores present in the pustules on the tubers. Under favorable conditions, the spores travel to other healthy tubers by means of air, water, or soil. It thrives in cool, wet conditions with temperatures between 53 to 63F (12-17C). Time of concern Early spring to summer Common hosts Potatoes Tomatoes