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Home > Diseases > Vegetable Diseases > Late Blight

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 symptom of late blight on potato leaves potato stem showing late blight
Fruit may develop a cottony, white mold growth. Spots start out pale green and turn brown to purplish-black. On stems, black and brown spots appear and spread. In high humidity entire veins can be killed quickly.
late blight on tomatoes tomato leaves with late blight tomatoes with late blight
Brown, leathery spots appear on green fruit on the top and sides. In humid conditions white mold will also form. In humid conditions a fuzzy mold appears on the undersides of leaves. Affected fruit often rots as secondary bacteria and fungi enter.

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Identification and Control Information (each will open in a new window)

More Information (each will open in a new window)

 

[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]

 
It is the policy of the State of Maine to minimize reliance on pesticides. The Maine Department of Agriculture and the Maine IPM Council encourage everyone to practice integrated pest management and to use pesticides only as a last resort. The mention of pesticides in the fact sheets linked to these pages does not imply an endorsement of any product. Be sure that any product used is currently registered and follow all label directions.