Cornell UniversityCollege of Agriculture and Life Sciences
Department of Horticulture
Department of Plant Pathology
  and Plant-Microbe Biology

Department of Entomology
CCE of Suffolk County
Long Island Horticultural Research and Education Center
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Serving the research and extension needs
of Long Island's horticultural industries.


Vegetable Pathology contact:

Dr. Meg McGrath
mtm3@cornell.edu
3059 Sound Ave.
Riverhead, NY 11901
(631) 727-3595
(631) 727-3611 (fax)

All photographs in this gallery were taken by Meg McGrath unless otherwise noted. For permission to use Meg's, please email her: mtm3@cornell.edu
 
New for 2012:

Late blight brochures for gardeners: New for 2011: 2010 updates: More late blight information:

Late blight on potato

Click on images for a larger view.

Return to disease photo index.


New for 2011:

Potato Late Blight video - Presentation about late blight and its management in potato by Steve Johnson, Extension Potato Specialist in Maine with years of experience with this disease.

Large leaf spots (lesions) are common with late blight. These were the main symptom seen in a commercial field on LI in 2009 when this disease was first found. The white growth on the leaf underside (see arrows, image below) contains hundreds of spores of the pathogen that could be dispersed by wind to other leaves in this field or beyond.

potato leaf blight

Upper leaf surface with late blight lesions (below)

potato leaf blight

Spores of the pathogen are visible on the lower (under) surface of leaves (below)

potato leaf blight

Close up of spores (below)

potato leaf blight

Leaf lesions can be small when they first start to develop (below left).

potato leaf blight

Symptoms also occur on other parts of potato plants including stems, petioles, and flowers. Following two photographs were taken on LI in 2006. White growth contains a lot of spores.

potato leaf blight

potato leaf blight

When first symptoms are mostly on stems (next two pictures below), it can be difficult to detect the onset of late blight, especially in a large planting as on a farm. All plant tissue above stem lesions will die shortly because the stem is completely affected, which is one reason that late blight is so devastating.

potato leaf blight

potato leaf blight

Below: tuber blight (Photo courtesy Dr. Steve Johnson, University of Maine Cooperative Extension.)

late blight on potato tuber

Below: tuber blight (Photo courtesy Dr. Steve Johnson, University of Maine Cooperative Extension.)

late blight on potato tuber

Below: tuber blight (Photo courtesy Dr. Steve Johnson, University of Maine Cooperative Extension.)

late blight on potato tuber

Below: tuber blight (Photo courtesy Dr. Steve Johnson, University of Maine Cooperative Extension.)

late blight on potato tuber

Return to disease photo index.


Copyright by the Department of Horticulture Website at Cornell University.