Late Blight Confirmed on Tomato and Potato in Pennsylvania
Posted: June 5, 2012
Symptoms of late blight on tomato include greasy gray-brown lesion on the upper leaf surface that develop whitish-gray sporulation on the underside of the leaf surface. (Photo: Beth K. Gugino)
Today late blight was confirmed in a commercial tomato field Blair County, PA and on both tomatoes and potatoes on the same commercial farm in Franklin County, PA. These are the first confirmed reports of late blight in Pennsylvania and on tomato in the region. There have also been several unconfirmed reports of late blight in commercial potato fields in Central PA. We are in the process of confirming these reports.
With the forecasted cool and wet weather it is very important to be using a protectant fungicide program at the very least. Commercial fungicide recommendations for managing late blight can be found in the 2012 Commercial Vegetable Production Recommendations Guide. Organic growers especially those in the central and south central part of PA should be applying a regular copper-based fungicide program. Copper is the most effective product if you are managing late blight organically. If you suspect late blight on your farm, please let me know via email at firstname.lastname@example.org or by phone at 814-865-7328.
The two previous reports of late blight on potato in central New Jersey and on Long Island have been determined to be US23. This is genotype was dominate one isolated in 2011 across the Northeast. US23 is characterized as the A1 mating type, pathogenic on both tomato and potato and is sensitive to the active ingredient mefenoxam (Ridomil). Samples from these most recent confirmations in PA are being sent to Bill Fry’s lab at Cornell for genotyping.
I also want to make you aware (or remind you) of another available resource to help you remain ahead of late blight. The USAblight website (http://usablight.org) was designed as a central portal for information on late blight. It contains information regarding where the latest outbreaks have been reported and one what crops. An alert system is also available that will send you email or text alerts that late blight has been confirmed within a personally defined radius from your location. There is also information about how to identify the disease and links to management recommendations.