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Late Blight

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Late blight symptoms on Tomato -
Symptoms of late blight on tomato Florida Department of Agriculture and Consumer Service. Division of Plant Industry.
Scientific Name: 
Phytophthora infestans (Montagne) Bary (ITIS)
Peronospora infestans Montagne (ITIS)
Common Name: 
Late blight (LB), late blight disease, potato late blight, tomato late blight
Native To: 
Possibly Mexico (Fry and Goodwin 1997)
Date of U.S. Introduction: 
First appeared in the U.S. in the 1840s; new aggressive strains of the disease were discovered in the 1990s (Fry and Goodwin 1997)
Means of Introduction: 
Possibly introduced through infected tomatoes imported from Mexico (Fry and Goodwin 1997)
Disease of potatoes and tomatoes (Fry and Goodwin 1997)
Current U.S. Distribution: 
Occurs throughout the U.S.


USDAAPHISPPQCPHST. Identification Technology Program.

ITP and the APHIS PPQ S&T Beltsville Lab are pleased to announce the release of IDphy: Molecular and Morphological Identification of Phytopthora Based on the Types, ITP’s first pathogen tool. This website offers PPQ and its partners the most complete, valid, and up-to-date resource for identifying the culturable species of Phytophthora. IDphy includes detailed standard operating procedures for all steps involved in culturing, sequencing, and identifying suspect samples, covering both molecular and morphological methods. Some species of Phytophthora are devastating plant pathogens that have a significant impact on agriculture and natural ecosystems.

USDA. National Institute of Food and Agriculture.
A national cooperative effort (funded by USDA-NIFA) on Late Blight of Tomato and Potato in the U.S. This site serves as an information portal on late blight. You can report disease occurrences, submit a sample online, observe disease occurrence maps, and sign up for text disease alerts. There are also useful links to a decision support system, and information about identification and management of the disease.

Distribution / Maps / Survey Status

USDA. National Institute of Food and Agriculture.


University of Georgia. Center for Invasive Species and Ecosystem Health.


Google. YouTube; Pennsylvania State University Outreach.

Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for Late Blight.

International Government
British Columbia Ministry of Agriculture (Canada).
See also: Field Vegetables for more fact sheets.

Manitoba Agriculture, Food and Rural Development (Canada).

State and Local Government

University of California. Statewide Integrated Pest Management Program.

Virginia Tech; Virginia State University. Virginia Cooperative Extension.

University of Alaska - Fairbanks. Cooperative Extension Service.

See also: UAF/CES Publications for more fact sheets.
North Dakota State University. Extension Service; University of Minnesota Extension.
Purdue University (Indiana). Extension.

Pennsylvania State University. Cooperative Extension.

University of Hawaii. Cooperative Extension Service.
See also: Plant Disease Publications for more fact sheets.
University of Hawaii. Tropical Agriculture and Human Resources. Integrated Pest Management Program.
University of Massachusetts - Amherst. UMass Extension. Greenhouse Crops & Floriculture Program.

Cornell University. New York State Integrated Pest Management Program.

National Center for Appropriate Technology. National Sustainable Agriculture Information Service.
International Potato Center.
American Phytopathological Society.