Pacific Pests, Pathogens and Weeds

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Summary

• 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.