Late blight has been identified in an early planted potato field on New York’s Long Island, raising the possibility that the contaminated seed potatoes came from Maine.

Meg McGrath, a plant pathologist at Cornell University, said in an interview that the farmer bought two varieties from Maine — Dark Red Norland and Superior — with symptoms of the fungus.

“We’re actually not sure of the source,” McGrath said. “There was a lot of late blight last year in seed productive areas, so it’s not a surprise it’s popping up. Most of our growers get their seed from Maine. It is the predominant supplier.”

But Eric Sideman, crop specialist with the Maine Organic Farmers and Gardeners Association, said there is no risk for late blight contamination in Maine from the Long Island field. The farmer has destroyed the plants showing symptoms and applied fungicides to protect the remaining plants.

“Maine is a large supplier of potato seed,” Sideman said. “Now that we know that late blight is in the region, and also that it probably came from Maine seed, people should be scouting their fields. I don’t think it was any particular farmer. Everybody that sells seed has a little bit of late blight. It’s an unlikely situation and we hope it won’t spread.”

McGrath said another possibility for the outbreak may be that the disease, which produces large brown spots, stayed in the ground during the winter. Maine growers have come to understand the disease and do a better job managing it, whereas New York growers don’t see it as often, McGrath said.

A 2010 outbreak in New York started because a gardener planted potato pieces bought at a grocery store, she said.

“It was unstoppable. What amazes me is it started with one gardener and it took over a whole area and jumped to Rhode Island and spread like wildfire,” she said.

The worse possible condition for spores spreading the disease is damp, cool weather, Sideman said. He said everyone, even backyard gardeners, should be looking at their potato plantings for late blight symptoms regardless of where the seed was bought.

“The most important thing is for people to be hearing about it in those areas where you don’t see it all the time, like southern Maine,” McGrath said. “It’s an extremely devastating disease. If people are worried about it and know there is the possibility they’ll stay on top of managing it and catch it early on in the season when it first starts.”

The most effective management strategy for late blight is to avoid sources of early season spores, according to Cornell’s website. Late blight can only survive on living tissues, so potato tubers — the part of the potato that’s eaten, rather than the stem parts — are the only source of early season spores. The website recommends planting healthy certified seed potatoes, use fungicides or buy resistant varieties.

Late blight is a plant disease that mainly attacks potatoes and tomatoes, although it can be found on other crops. It was a factor in the Irish potato famine, which began in 1845.

“It is controllable,” McGrath said. “But if you’re not on top of it, you can’t stop it. A major concern are small growers in the state and gardeners who don’t know about the disease who are not going to take enough action.”

Sideman said people who suspect late blight should take photos and send them to him at esideman@mofga.org or their county extension.

Mechele Cooper — 621-5663

mcooper@centralmaine.com