Fusarium dry rot – Fusarium spp., fungus
Dry rot is an appropriate description of this very common disease. Sunken and often shriveled areas on the surface of infected tubers are the most obvious symptom. When tubers are cut through the affected areas, tissues appear brown and collapsed, often with a white, pinkish, or yellow fungal growth, which may extend into the center of the tuber. Infection may occur anywhere on the tuber surface, including the stem end. Diagnosis of this disease can become complicated when secondary organisms, often soft rot bacteria, invade the infected tissue and a wet rot of the tuber results. Seed tubers infected with Fusarium spp. produce plants with reduced vigor and may result in poor stands. Infection can be minimized by avoiding tuber bruising during harvest and grading, and providing appropriate conditions for suberization (high humidity and good ventilation early in storage). Fungicide applications to seed before storage and at planting are also recommended.