Late Blight fungus spreading north from the South Fork

A highly contagious fungus known as late blight has been found on the East End, and researchers say farmers could experience the most severe and devastating case of it in recent years.

Meg McGrath, associate professor of plant pathology and plant microbe biology at the Cornell Extension Center in Riverhead, said the deadly fungus has spread here from the South Fork and continues to move across Long Island farms via wind and rain.
“I hope we don’t see any devastation for growers,” she said. “But it is going to cost them more this year.”

Long Island Farm Bureau executive director Joe Gergela said while farmers will have to spend more on spraying their crops with fungicides, he doesn’t believe it will increase consumer prices because of chain store competition.

“Hot days and cool nights make it ripe for various problems,” Mr. Gergela said. “It’s part of farming and we’ll deal with it.”
As of July 8, the pathogen had become fairly widespread on Long Island — creating the most severe outbreak in the country — and is expected to spread to New England, Dr. McGrath said.

Late blight is the same deadly fungus that destroyed Ireland’s potato crop during the mid to late 1840s.

This year, it was first found in a Sagaponack garden and spread throughout the Bridgehampton area, Dr. McGrath said. While mild cases of late blight have popped up in crops and gardens on Long Island in recent years, the last severe case occurred in 2007, when it surfaced in Wading River and traveled south.

“We think in that case a storm brought it over here from a known case in Pennsylvania,” Dr. McGrath.

Late blight is something every farmer looks out for during the growing season. The disease is particularly widespread this year due to the unusually wet conditions throughout the month of June. If the weather dries up, late blight could just as easily disappear.

Dr. McGrath believes the pathogen moved up from the South Fork after a late June rainstorm onto farms and gardens in an area from Southold through Baiting Hollow.

“It’s really amazing to see just how this disease can take off,” she said.

Following Friday’s storm, researchers are investigating other parts of Long Island to see where else the fungus has landed.
On Tuesday, a Mattituck resident sent a sick plant over to Dr. McGrath that tested positive for late blight.

The Cornell Extension Center won’t release the locations of affected home gardens and farms for privacy reasons. The current pathogen strain is believed to be different from those associated with late blight in previous years, but the source has not been identified yet, Dr. McGrath said.

The destructive fungus attacks only plants in the nightshade or potato family, including tomatoes, eggplants and petunias. Brown spots, or lesions, appear on the stems and leaves of infected plants, producing a white fungal growth in moist weather that rots the plant. At times, the lesion border may appear yellow or water-soaked.

Late blight spores spread fastest under wet conditions. Air currents will pick up the spores in clouds and rain will deposit them miles from their origin, making the disease difficult to contain and to trace.

Dr. McGrath recommends having your crop or garden checked out if you believe you have late blight.

“We consider it a community disease,” Dr. McGrath said. “Your one little patch of late blight could have a tremendous impact on others around you growing tomatoes and potatoes.”

For more information, visit Dr. McGrath’s website at

[email protected]

BARBARAELLEN KOCH PHOTO | Dr. Mark Bridgen, director of Cornell University Long Island Horticultural Research and Extension Center in Riverhead, shows that late blight hit the tomato plants in the Victory Garden there about 10 days ago.