If high temperature and humidity occur at this time, much of the foliage is killed and falls off. Tubers may be infected with brown, corky, dry spots. The fungal spores spend the winter in plant debris left in the garden, and on other solanaceous hosts, such as tomato, eggplant and black nightshade. Tubers are frequently infected through wounds inflicted during harvest. Allow tubers to mature fully before digging.
Infected tubers are inedible.
Remove diseased plants immediately after harvest. Use disease-free seed potatoes. For fungicide application, see late blight. This disease is caused by the bacterium Streptomyces scabies , which persists in the soil for long periods. Brown corky scabs or pits occur on potato tubers.