Widespread. Africa, Asia, North, South, and Central America, the Caribbean, Europe, Oceania. In Australia, Fiji, New Caledonia, Papua New Guinea.
Serious outbreaks reported. On rice mainly and wild grasses.
Symptoms occur near water level at heading and gain filling: stem rot, chalky grains and unfilled panicles.
Infection begins when floating minute fungal balls (‘sclerotia’) infect leaf sheaths, causing black spots and rots, lodging of stems, and production of spores (‘conidia’, ‘ascospores’, sclerotia) inside leaf sheaths. Insect damage and too much N and too little K increases disease.
Spread as sclerotia in water and on seed. Survival as sclerotia in straw and stubble in soil.
Cultural control: frequent ploughing before sowing; possibily liming soil; drain fields occasionally to reduce sclerotia; ensure correct N:K balance, and split fertilizer applications; collect straw and burn, or plough in stubble and straw after harvest; rotate with forage or legume crops.
Chemical control: unlikely to be economic, although recommendations include copper hydroxide, fentin hydroxide, thiophanate-methyl. Possibly insect control should be given priority.