May 31, 2006 | By: Laura Skillman

Every year in Kentucky, blue mold makes its way into some of the state’s tobacco patches. The first reported case of the disease this year was identified in Magoffin County this past week, followed by cases in Morgan and Boyle counties.

The Magoffin County plants came from an outdoor float bed, and appeared to have been infected for more than a week, said Kenny Seebold, plant pathologist with the University of Kentucky College of Agriculture. 

“We’re not sure of the source of this outbreak, as no blue mold has been reported in the U.S. until last week,” he said. “The general feeling is that blue mold doesn’t overwinter in Kentucky, so any blue mold that develops here must move in from outside the state. It is possible that the blue mold pathogen could survive in a protected environment such as a greenhouse, however, and this could serve as a source of inoculum for an outbreak. Tobacco seedlings brought into Kentucky from a region where blue mold is active could be a source of the blue mold pathogen as well.” 

Seebold said producers need to make sure that any tobacco in float beds (outdoor and greenhouse) are treated with Dithane DF or Aliette to protect against blue mold. This is especially important for tobacco in eastern Kentucky, but would also be a good measure of insurance for the rest of the state.

Growers who have been applying Dithane DF regularly to protect against target spot and anthracnose will also achieve suppression of blue mold. Since Dithane is a protectant, it needs to be in place prior to the arrival of inoculum for best effect. This means preventive applications are the key for success. Aliette WDG is cleared for use on tobacco seedlings and has better activity than Dithane against blue mold, but none against target spot or Sclerotinia collar rot. Apply as a fine spray to achieve thorough coverage. 

Once in the field, plants can be treated with Dithane DF plus Acrobat 50 WP or Actigard. Plants need to be at least 18 inches tall before receiving an application of Actigard, and the material should be applied three to five days before infection for the product to effectively work.

The forecast for the next week to 10 days calls for warmer-than-normal temperatures, mostly sunny days, and chances for showers. The warmer temperatures and sunny days will help slow the spread of blue mold. However, there is definitely a risk of spread to areas close to the recently discovered cases, particularly in areas that are shaded for any length of time during the day, Seebold said.

“I hope we are dealing with some isolated cases of blue mold, but we all know that anything can happen now that the ‘cat is out of the bag’,” he said.

Information on blue mold and other diseases can be found at the Kentucky Tobacco Disease Information Web site.


Kenny Seebold, 859-257-7445, ext. 80721