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Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

Tobacco brown spot (306)

Photo 1. Brown spot of tobacco. In this instance, the cause is given as Alternaria alternata. Pale brown spots, with darker margins and yellow halos.

Photo 2. Brown spot of tobacco, Alternaria alternata. Close-up a single spot, showing faint target-like rings.

Summary

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.

Common Name

Tobacco brown spot

Scientific Name

Alternaria longipes. Note, that some accounts give the name of brown spot on tobacco as Alternaria alternata.

AUTHORS Grahame Jackson & Eric McKenzie
¹Dingley JM et al. (1981) Survey of agricultural pests and diseases. Technical Report. Volume 2. Records of fungi, bacteria, algae and angiosperms pathogenic on plants in Cook Islands, Fiji, Kiribati, Niue, Tonga, Tuvalu and Western Samoa. FAO, Rome, Italy; and Information from Brown spot (Alternaria longipes) Plantwise Knowledge Bank. (http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=4514). Photo 1&2 R.J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company, Bugwood.org.

Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.

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