Worldwide distribution. A primary pathogen on tobacco, but a wound pathogen of many others. A minor fungal disease.
Leaf spots, small, round at first, expanding as leaves mature, up 25 mm diameter, zoned, first on the lower leaves. Spots merge, and centres fall out. Upper leaves infected on susceptible varieties.
Spread by airborne spores, or spores splashed by water onto lower leaves; spread by seed containing infected leaf pieces. Survival in plant debris.
Cultural control: note similarity with tobacco frog-eye (see Fact Sheet no. 304); resistant varieties; check nursery plants free from disease; avoid overlapping crops, or plant far from crops with disease; avoid overhead irrigation; weed; remove volunteers; remove infected leaves; apply balanced NPK; collect and destroy debris after harvest; crop rotation.
Chemical control: use mancozeb, copper or chlorothanonil.