Powdery Scab
Spongospora subterranea
Other
Roots
Fruit
Overview
A soil-borne disease of potatoes caused by a protist, producing raised, powdery pustules on tubers and root galls. Also serves as a vector for Potato mop-top virus.
Symptoms
Raised, circular pustules on tuber surfaces that rupture to release powdery brown spore balls. Root galls. Cankers on stolons. Tubers may crack. Reduces tuber quality and marketability.
Environmental Conditions
Cool
Prevention
Use certified disease-free seed potatoes. Rotate potatoes on a 5+ year cycle. Improve drainage. Avoid overwatering. Plant resistant varieties. Maintain soil pH below 5.5.
Management
Long crop rotation. Improve drainage. Avoid overwatering. No effective chemical control. Remove infected tubers. Clean and disinfect equipment.