Late blight on a tomato plant | Courtesy Cornell University horticultural research laboratory
Late blight on a tomato plant | Courtesy Cornell University horticultural research laboratory

Late blight, the plant disease that caused the Irish potato famine, has been found in a crop of tomatoes in Riverhead this week, and Cornell University’s Riverhead research lab is urging home gardeners to check their tomatoes for late blight lesions, in order to avoid the spread of this fast-moving, spore-spread disease.

Late blight, which only affects tomatoes and potatoes, has become somewhat endemic on the East End over the past several years, cancelling tomato tasting contests and wreaking havoc in home gardens, but it is appearing on the scene relatively late this hot, dry summer: the first patches of late blight were discovered here in May last year.

Many commercial growers have taken to spraying copper sulfate fungicide on plants at the first sign of the damp weather that provides ideal growing conditions for late blight spores and helps spread them on the wind to other farms.

Dr. Meg McGrath, who studies late blight for Cornell University, sent an email to gardeners late Thursday warning that “A very few lesions were found this afternoon in a crop of tomatoes that has been part of the Late Blight Scouting Program.”

“This outbreak could be the result of spore dispersal during a recent storm.  It is quite possible other crops are affected as well,” she added. “All tomato and potato crops need to be inspected for symptoms. It is critically important to report suspect occurrences so that we all know the extent of the outbreak. Additionally, affected tissue needs to be examined to determine what strain(s) of the pathogen are present. The symptoms found today were not characteristic leaf spots of late blight but rather large v-shaped dead areas, resembling those caused by drought stress; however, the tissue had a small light green wilted border with a small amount of white fungal growth of the late blight pathogen on the underside that was barely discernible without magnification.  These features are both characteristic of late blight and so attracted the attention of the scout.”

Home gardeners are being urged to call Cornell’s diagnostic lab if they have any suspicions late blight might be present in their gardens, Monday through Friday, from 9 a.m. to noon, at 631.727.4126.

The Cornell laboratory has an exhaustive amount of data and research on late blight available here.

Beth Young
Beth Young is an award-winning local journalist who has been covering the East End since the 1990s. She began her career at the Sag Harbor Express and, after receiving her Masters from the Columbia University Graduate School of Journalism, has reported for the Southampton Press, the East Hampton Press and the Times/Review Media Group. She founded the East End Beacon website in 2013, and a print edition in 2017. Beth was born and raised on the North Fork. In her spare time, she tinkers with bicycles, tries not to drown in the Peconic Bay and hopes to grow the perfect tomato. You can send her a message at

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