A fungus that caused the Irish potato famine of the late 1840s is hitting Kentucky tomatoes this year.
The disease, called late blight or Phytophthora (Latin for “plant destroyer”) infestans, is rarely found in Kentucky, and it usually doesn’t show until later in the growing season. But it’s been causing problems in the eastern United States this summer and has shown up in several places in Kentucky.
It likes cool, wet weather, which we’re had plenty of, said Kenny Seebold, an extension plant pathologist with the University of Kentucky’s College of Agriculture.
Most of the cases have been from Eastern Kentucky, he said.
The first reports, from back-yard gardeners, started coming in right after the Fourth of July. The first case from a commercial grower came in Monday, Seebold said. It involved a farmer near Morehead who was growing a half-acre of tomatoes and lost about 90 percent.
“It was pretty severe, so we’re worried it’s taking hold,” Seebold said.
The leaves of infected tomato plants wither and die quickly, he said. Most diseases start at the bottom of a plant, but late blight can attack the entire plant or start at the top.
Look for nickel-size olive green or brown spots on leaves and slightly fuzzy white fungal growth on the underside. Lesions appear on stems. Firm, brown spots develop on tomato fruit. To see photographs, go to www.hort.cornell.edu/department/Facilities/lihrec/vegpath/photos/lateblight_tomato.htm.
Farmers and gardeners are advised to inspect tomato and potato plants for signs of trouble. Seebold suggests preventative applications of chlorothalonil or mancozeb. Because the disease is rare here, most suppliers don’t carry the chemicals necessary to treat a plant that already is infected.
Growers who suspect that the blight is already present should take samples of the plants to their local extension office so UK plant pathologists can diagnose them.
Reach Andy Mead at (859) 231-3319 or 1-800-950-6397, Ext. 3319.