How to Manage Pests
UC Pest Management Guidelines
Fusarium causes a dry rot of infected tubers, although a moist rot may occur if secondary infection by soft rot bacteria is also involved. Initially, lesions appear as brown to black flecks on the tuber surface. Lesions later form large, hollow cavities. Frequently, the lesions appear wrinkled on the tuber surface with numerous white tufts of mycelium. Infected seed pieces may completely decay.
Fusarium spp. are present in all soils and are found on the surface of all tubers. Wounds are required for infection. Fusarium cannot penetrate intact tuber skin, lenticels, or suberized (healed) seed pieces.
Proper handling and curing is usually sufficient to give economic control of dry rot in storage. Allow tubers to mature before harvest and prevent bruising tubers during harvest and storage operations. Wound healing reduces infection by Fusarium; to speed the healing process, hold tubers at 50° to 60°F with good ventilation and a relative humidity of at least 95% for the first 2 to 3 weeks of storage. Fresh market tubers should be stored at 38° to 40°F with 90 to 95% relative humidity and adequate ventilation.
Seed piece decay is reduced when seed pieces are planted under conditions that favor rapid suberization; Fusarium cannot infect cut surfaces after they are suberized. Warm the seed tubers to 50°F before cutting, and keep cutting and handling equipment disinfected. Plant when the soil temperature is at least 45°F and when soil moisture is 60 to 80% of field capacity. If possible, avoid irrigation before emergence. When planting conditions are likely to favor seed piece decay, treat cut seed pieces with a fungicide.
UC IPM Pest Management Guidelines: Potato