SOMERSET—So far there’s been no reports of the late blight on tomato or potato plants in Somerset County.
“Cross your fingers, find some wood to knock on,” said Miguel Saviroff, educator with the Penn State Cooperative Extension in Somerset County. “Not even one phone call about it this year.”
Tom Ford, commercial horticulture education with Penn State Cooperative Extension in Blair County, said the only report of blight that he has received this year was on a potato crop in Loretto.
“The weather is not conducive to blight and the commercial growers are continuing to treat against it,” he said. “This bodes well for both homegrowers and commercial growers.”
The potato blight found in Loretto was discovered two weeks ago. The blight strain isn’t as aggressive as the strain in 2009 when blight killed most of the tomato crop in Pennsylvania. The outbreak was bad in 2010 as well, but not as severe as the previous year. Late blight is a destructive fungus that becomes airborne and spreads from one garden to another.
Growers should not become complacent.
“Continue to be vigilant,” Ford said. “Don’t be lulled into a false sense of security. I’m concerned about a cold front in Somerset County — if you have cooler nights, and I mean in the 50s, we could still have an explosion (of blight) late in the season.”
“I’m concerned because of the cool nights — remain watchful,” he said. “These extreme temperature swings can be a problem. Keep your eyes open.”
Gardeners should use a fungicide that contains chlorotalonil or macozeb as soon as the plant reaches 6 inches tall. Home gardeners aren’t able to purchase as strong a fungicide as commercial growers can buy. Organic gardeners may try fixed copper as a treatment, but Ford said organic gardeners had a lot of trouble with blight in 2009.
Late blight starts out as a greenish gray to black spot or lesion on the leaf surface. It progresses to dark black or brown lesions on the stems. They gray spores develop on the underside of leaves.
Gardeners who detect the disease should cover the entire plant with a black plastic bag to kill the spores, Saviroff said, then pull the entire plant — roots and all — out. Close the bag and place it on a cement sidewalk in a sunny area for a day or two so the spores are baked. The bags can then be put out with the garbage. Plants should not be placed on compost heaps.
People who aren’t sure if their plants have blight may take a specimen to the cooperative extension office or e-mail the office a photograph. The local extension office e-mail is SomersetExt@psu.edu.