Worldwide distribution. Tropics and sub-tropics. On lettuce, and relatives in daisy family, including weeds. Occasionally, an important disease.
Spots circular to oval, brown, with whitish centres, up to 1 cm. Later, merge. On older leaves first.
Wet weather disease; spores spread in wind and rain.
Cultural control: in nurseries – keep free of weeds and avoid overcrowding; in field – space plants to allow air movement; drip irrigation; weed; 2-3-year crop rotation; avoid overlapping crops; collect and burn trash after harvest.
Chemical control: likely that cultural practices sufficient; if fungicide needed, use mancozeb.