Reportedly, tests revealed blue mold spores on nine acres of a farm near Cecilia, Kentucky, 45 miles southwest of Louisville.
One expert says hot, dry weather appears to be preventing it from spreading.
University of Kentucky tobacco pathologist Kenny Seebold says, "With that one report, we're very, very concerned that we have it in other places."
Mold spores may have been carried by Tropical Storm Arlene, which moved through the area earlier this month.
A blue mold outbreak in 1996 cost Kentucky growers an estimated $200 million. Last year, the disease moved quickly through the state and was confirmed in more than 40 counties by July. But, it did not significantly affect the tobacco harvest.
Before Seebold's report, the North American Plant Disease Forecast Center had not received any reports of blue mold in the United States.
