Additional late blight outbreaks confirmed in New York and now also in Pennsylvania!

Posted: July 7, 2011

Today we confirmed late blight on a potato sample from a commercial field in Cambria County.
Foliar symptoms of late blight on potato (Photo: Beth K. Gugino)

Foliar symptoms of late blight on potato (Photo: Beth K. Gugino)

Today, we confirmed late blight on a potato sample collected from a commercial production field in Cambria Co., PA. Heavily sporulating foliar and stem symptoms were observed. The outbreak is confined to a small hot spot in the field and the grower will continue to manage the crop using late blight specific fungicides. The sample has been submitted for genotyping.

Since the update last week, late blight has also spread from South Fork to the North Fork of Long Island, NY where there have been on additional reports of late blight confirmed in several tomato plantings (commercial, gardens as well as research fields at LIHREC) according to Meg McGrath, vegetable pathologist at Cornell.

The pathogen is typically thought to have a maximum spread of 30-miles from the source. Ideal conditions for late blight are daytime temperatures between 60-75F and nighttime temperatures between 50-60F, accompanied by fog, heavy dews or rain over a four to five day period. Extended periods of high relative humidity are also important for disease.

Remember that late blight is a community disease! If you suspect late blight please contact your local Penn State Cooperative Extension Office, the Penn State Plant Disease Clinic or Beth Gugino at or 814-865-7328. Updates will continue to be posted on this Vegetable and Small Fruit Extension Team website and audio-messages posted on the 1-800-PENN-IPM hotline under the tomato/potato. For the most current map of confirmed late blight outbreaks please visit