Worldwide distribution. On rice and wild grasses. An important disease.
Spots oval or diamond-shaped, 5-15 mm, with whitish-grey centres and dark brown borders, merging, killing the leaves. Rots of leaf sheath, stem and panicles. Plants killed until tillering stage.
Spread of spores in irrigation water and by wind.
Cultural control: sow to avoid flowering at wettest times; avoid overlapping crops; split N applications; space plants to maximise air flow; collect and burn trash after harvest. Use chemicals at heading stage.
Chemical control: Seed/field treatment: mancozeb, captan (protectants); azoles, strobilurins (eradicants).