Late blight, the disease that five years ago wiped out much of the tomato crop of commercial and residential growers in the region, has turned up in Cambria and Somerset counties.

While the 2009 spread of the pathogen Phytophthora infestans was devastating, indications are the disease could be even more far-reaching this year, according to Tom Ford, Penn State Extension horticulture educator.

“It has the potential of being huge,” Ford said late last week.

Often referred to as late tomato blight, it was first detected about a month ago in a commercial potato field in northern Cambria County.

Since that time it has been detected in Blair County and by midweek was confirmed in a tomato field of a commercial grower in Bedford County.

“We’re seeing it significantly in commercial fields,” Ford said. “In Bedford County, one farmer had his entire cherry tomato crop wiped out.”

At about the same time the blight was discovered in the Cambria County potato field, it also was detected in fields in Lancaster and Chester counties, he said.

The blight starts with a greenish-gray to black spot or lesion on the leaf surface, he said. As it progresses, dark brown to black lesions will develop on the stems of the tomato or potato plant, followed by gray-colored pores on the underside of the leaves.

While modern treatments likely would prevent any type of massive crop loss, Ford said growers and gardeners should not lose sight of the fact that the blight is the same one that caused the Irish potato famine of the 1840s.

Commercial vegetable grower Jim Benshoff of Summerhill said he struggles annually to stay ahead of the blight, which favors cooler temperatures and thrives when there is plenty of moisture.

“If you can get it to leave, you’d get a gold star,” Benshoff said. “You’ve got to be as proactive as you can. You cannot be on the defensive.”

As soon as he got word of the blight, Benshoff said he contacted scores of other growers, in an effort to slow the spread of the pathogen that often moves with ease from one farm to another.

It spreads by spores in the air, and once the blight is evident, it’s too late to save the plant. But extreme measures often can diminish its spread, experts said.

Ford and others recommend carefully removing the diseased plants, immediately putting them in trash bags and leaving them in the sun, then setting them out with the trash.

“Under no condition should the gardener make any effort to compost plants infected with late blight,” Ford said.

The spores, when mature, he said, can be picked up by animals and people, blown by the wind and carried on tools or cultivating equipment to other susceptible plants.

Concern is increasing over farms in the Amish community of Sinking Valley in Blair County, Ford said.

“We’re seeing tomato fields going down; we’re seeing potato fields going down,” he said.

While commercial growers have access to a wider variety of chemicals to treat the plants, Ford said residential gardeners can apply fungicides such as chlorothalonil, mancozeb or a mixed copper to uninfected plants every five to seven days.

Upper Yoder Township gardener Ron Kohler, who is part of Penn State’s Master Gardener program in Cambria County, said the group had received no samples as of Thursday.

“But I suspect we’ll be getting them shortly,” he said.

Kohler and other gardeners he knows are spraying and “keeping our fingers crossed.”

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