Aug 18, 2015
Late blight confirmed in Pennsylvania

Today late blight was confirmed in a commercial tomato field in Berks County, Pennsylvania near Fleetwood. This is only the third county that late blight has been confirmed in Pennsylvania so far this season. A sample is being sent to Cornell University for genotyping.

There are a lot of tomatoes and potatoes being grown in the Berks County area so make sure that you are scouting for late blight. 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 2015 Commercial Vegetable Production Recommendations for a list of recommended late blight specific products for both tomato and potato and always read the label prior to application and follow pre-harvest intervals. For organic production, growers should be using a regular copper-based fungicide program. Copper is the most effective product if you are managing your crop organically and can be used in a program that also includes Actinovate and Regalia.

If you suspect late blight on your farm, please contact your local Penn State Extension Office or let me know via email 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. 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

— By Beth K. Gugino, Associate Professor Vegetable Pathology, Penn State University

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