Late blight threatens Vt. plants

VERMONT — Gardeners beware: Late blight, which last swept tomato and potato plants in the state in 2009, has been confirmed in Vermont this year.
The University of Vermont Extension on Aug. 3 announced a case of the late blight on tomato plants in a home garden in Jericho.
Vern Grubinger of the UVM Extension said he’s spoken with a couple more people in that area who are sending their plants in for testing, but that there have been no other confirmed cases in the state.
Late blight can affect plants of the nightshade family, but has only been seen on tomatoes and potatoes in the state. The disease is credited with causing Ireland’s Potato Famine in the mid-1800s by destroying potato crops across the country.
In 2009, the unusually wet weather aided the blight in spreading to farms and gardens across Vermont. Wet and dewy weather can speed the spread of late blight, UVM Extension advises home gardeners and farmers to be vigilant in searching for signs and symptoms of the disease. Once a plant is infected, the spores can travel on the wind to neighboring plants and longer distances.
Especially in wet weather, gardeners are advised to check plants daily for what the release describes as “nickel-sized water-soaked spots” on the tops of the leaves and “whitish-gray fungal growth” on the bottoms of the leaves.
Tomato fruits on infected plants will eventually develop large brown spots, but Grubinger said late blight is harmless to humans.
“It’s not going to hurt you if you eat some of it, but it can cause a lot of crop damage,” he said.
UVM Extension notes that fruits from infected plants should not be used for canning.
As late blight can only live on live plant tissue, the release advises that farmers and gardeners cut and burn the plants, or turn them under the soil to decompose. Vines on potato plants that aren’t severely infected can be cut, and their tubers left in the ground for two to three weeks to limit the danger of late blight spores.
Grubinger said it’s simply not enough to ignore an infected plant, for the sake of other plants in the area and other growers in the region.
“It’s especially important to avoid spreading the disease to people who are making a living off of their plants,” he said.
Spencer Blackwell of Elmer Farm in Middlebury said he grows most of his tomatoes in the more sheltered environment of a hoophouse, but that he doesn’t use fungicides to ward off late blight. Right now, he, like many other growers in the Champlain Valley, is watching and waiting.
“I really don’t do anything — just hope for the best,” said Blackwell. “I’m just going to sell tomatoes until then.”
For more information about late blight and plant testing, contact the Vermont Master Gardeners at or 1-800-639-2230.
Reporter Andrea Suozzo is at [email protected].

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