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Late Blight Confirmed on Potato on Long Island, NY (and also in NC)

Posted: June 23, 2014

First confirmed reports of late blight this summer are on potato in New York and North Carolina.

Late blight was confirmed in one potato field in Long Island, NY this past Friday, June 20th. According to Cornell Vegetable Pathologist, Dr. Meg McGrath, a few scattered symptoms were observed in a small area in the center of the field. Two adjacent plants had more foliar symptoms plus stem lesions, but not to the extent that would be expected if infected seed was the potential source. The growers was using protectant fungicides and since the confirmation has applied late blight specific fungicides. On Thursday June 19th, late blight was also confirmed in a potato field in Carteret County, NC which is near the coast. Aside from reports in Florida this past winter, these are the first late blight reports of the season along the east coast.

Symptoms on tomato and potato are very similar and any growth stage is susceptible. Also keep in mind that crops grown under high tunnels and other protected structures are not immune from getting late blight. Scout your fields vigilantly. If using late blight specific fungicides, check corners of fields, areas of the field where you have a more difficult time getting good fungicide coverage with your sprayer, and areas where the foliage tends to remain wet the longest (lower lying shadier areas). This is where late blight symptoms are typically seen first. Protectant fungicides will only protect the crop at the site of application so thorough coverage is critical.

In fields where late blight has been confirmed, rogueing or burning down the most severely infected plants or portion of the field will reduce the build-up of inoculum and the potential for spread within the field, between fields and between farms. Incorporating the use of late blight specific fungicides will further reduce the development of new lesions and spread of the disease. Products like Tanos (famoxadone + cymoxanil) and Curzate (cymoxanil) have a slight amount of “kick-back” activity and are effective at managing every early stages in the infection process (all of which are invisible to the naked eye). Applications of these products need to be followed-up with an application a fungicide from another FRAC code group. See the 2014 Commercial Vegetable Production Recommendations for a list of recommended late blight specific products for both tomato and potato. For organic production, copper hydroxide still remains the most effective crop protection tool.

If you suspect late blight on your farm, please contact your local Penn State Extension Office or let me know via email at bkgugino@psu.edu or by phone at 814-865-7328. We are interested in collecting samples so we can better understand how the pathogen population is changing both within and across growing seasons. Additional images of late blight on tomatoes and potatoes can be found under the Vegetable and Small Fruit Diseases link in the left-hand navigation column. Also for the information regarding where the latest confirmed outbreaks have been reported and to receive email or text alerts about when late blight has been confirmed with a personally defined radius from your location visit USAblight.