Worldwide distribution. On potato, rice, and more. Many strains. An important disease.
Brown sunken cankers on stems and stolons, limiting tuber growth and causing wilts, stunting and death. Balls of fungus in black rinds ('sclerotia') on tubers. It also causes seedling damping-off.
Spread in movement of soil and seed.
Cultural control: certified seed; best to sprout seed, inspect, then plant; remove volunteers; avoid, cold wet soils and plant only 5 cm deep so that the warm soil encourages rapid shoot growth; improve field drainage; manure; 3-year rotation; harvest as soon as tops removed; collect and burn trash after harvest.
Chemical control: seed - treat with pencycuron or mancozeb.