(Dearborn County, Ind.) - Dearborn County garden growers ought to keep an eye on their tomato plants.

Tomato plant infected by late blight. Purdue University Plant & Pest Diagnostic Laboratory

Purdue University’s Plant & Pest Diagnostic Laboratory confirmed June 30 a case of the late tomato blight in Dearborn County. It’s the first such case in Indiana this year.

The fungal infection which can travel up to 40 miles by air was found in plants in a home garden near the Ohio River. It was located previously in Boone County, Ky.

"Late blight is a very damaging disease of tomato and potato," said Dan Egel, Purdue Extension plant pathologist at the Southwest Purdue Agricultural Center in Vincennes. "The disease can spread very rapidly under cool, moist conditions, and this latest outbreak may have spread during recent rainy weather."

The late blight causes tomato plants to develop brown lesions with white borders on their leaves and discolors the fruit.

Growers cannot do much to stop the blight from affecting plants. Fungicides may slow the progress of late blight, Egel said. Retail products that contain the active ingredient chlorothalonil may reduce the spread of the disease if applied on a regular basis. Trade names include Bonide™, Daconil™, Exotherm Termil™ and PathGuard™.

Organic growers should use copper products, Egel said.

In 2009, the late blight spread to 30 Indiana counties – the first outbreak since 1998.

"I don't think it will be as bad as last year because in Indiana late blight appears to be spreading by natural movement rather than multiple introductions via infected transplants," said Tom Creswell, director of P&PDL. "Of course, it could be locally severe if weather is favorable for disease development and the pathogen is present in an area."