Late Blight—Phytophthora infestans

Late Blight is caused by a fungal-like pathogen. It causes blighting and death of tomato and potato plants during cool, wet weather.

** Late Blight is a very serious disease. If you suspect Late Blight in your garden, please contact the University of Maine Cooperative Extension, Pest Management Office at 800-287-0279 **

late blight on potatoes
Fruit may develop a cottony, white mold growth.

symptom of late blight on potato leaves
Spots start out pale green and turn brown to purplish-black.

potato stem showing late blight
On stems, black and brown spots appear and spread. In high humidity entire veins can be killed quickly.

late blight on tomatoes
Brown, leathery spots appear on green fruit on the top and sides. In humid conditions white mold will also form.

tomato leaves with late blight
In humid conditions a fuzzy mold appears on the undersides of leaves.

tomatoes with late blight
Affected fruit often rots as secondary bacteria and fungi enter.

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Identification and Control Information

More Information

[Photos, left to right: G.D. Franc, Bugwood.org; Howard F. Schwartz, Colorado State University, Bugwood.org; Howard F. Schwartz, Colorado State University, Bugwood.org; Robert Wick, University of Massachusetts, Bugwood.org; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org]