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GAZETTE FILE PHOTO

A blight-infected tomato plant.

HADLEY - The blight that devastated tomato plants in the Pioneer Valley last summer has been found on a farm in Hadley, according to vegetable specialist Ruth Hazzard.

The farm where late blight was found was The Next Barn Over on Lawrence Plain Road in Hadley, said Michael Docter, who rents the land to farmers Ray Young and Tory Field. They have plowed under the tomato crop in an attempt to prevent the blight from spreading, said Hazzard, who works for UMass Extension.

Backyard tomato growers should consider spraying their crops with fungicides to prevent an infestation and inspect the plants regularly for symptoms of late blight, she said. Tomatoes infected with late blight have at least nickel-sized dark green or brown lesions on the leaves and brown lesions on the stems.

If the lesion has a yellow border and occurs on the bottom of the plant, it is probably caused by early blight or Seeptoria leaf spot, according to Hazzard.

Organic farmers may want to spray tomatoes with liquid copper or a product called Serenade Solutions, said Danny Ziomek, nursery manager at Hadley Garden Center. These products should be sprayed every five to seven days, at least 12 hours before rainfall or after heavy rain, he said.

The main chemical control for late blight is Daconil, which does not need to be sprayed as often, he said.

"I'm shocked," said Ziomek. "You usually look for more disease problems in rainy weather. The spores could have been left around, and all it takes is a plant left on the edge of a field, and you can get a re-infection."

Last year, June and July were uncommonly cool and rainy, which are the ideal conditions for late blight. Starter plants infected with the fungus in the South were distributed in the Northeast, mainly at chain stores.

This year, the problem for farmers until recently has been not enough rain.

"These night rains make for good disease conditions, so folks should be alert," Ziomek said. "There could be a whole new infection brought by storms coming from the South."

Gardeners who detect late blight one tomato plant should pull them all up and bury them in a hole, he said.

"We've been crossing our fingers through this hot and dry summer, because last summer was such a hard one," said Margaret Christie, special projects director at Community Involved in Supporting Agriculture in South Deerfield. "We went through such a bad year last year, it seemed like the odds were we would not have late blight this year. It began to seem we might escape it."

She said she suspected that the fungus could have survived in overwintering potatoes. Late blight can also be found in potatoes.

Late blight is a fungus that is similar to the one that caused the potato famine in Ireland in the 1840s. Once late blight is present, it can produce billions of spores that are carried by the wind and can infect tomato plants in a 30-mile radius, said Abby Seamon of the New York Extension Service at a forum in Amherst last summer.

As of July 6, there had been no cases of late blight reported in New England, not even in Maine, where the weather had been cooler and rainier, Hazzard wrote on the Extension website.

Tomato plants started from local seed should be free of the disease, but can acquire it from spores in the wind. Some tomato varieties are resistant to late blight, such as Mountain Magic, Plum Regal and Legend.