May 19, 2004 | By: Laura Skillman
LEXINGTON , Ky.

For 25 years, farmers across Kentucky and beyond have come to rely on the Kentucky Blue Mold Warning System for timely information about this destructive and explosive tobacco disease.

The system is an educational program of the University of Kentucky Cooperative Extension Service under the direction of William Nesmith, UK Extension plant pathologist.

Blue mold is a very weather-sensitive disease that spreads both locally and over long distances through the air and on transplants. It is introduced each year from its over-wintering sites primarily via infected transplants or airborne spores from the south or southwest, Nesmith said. Once introduced, it remains active until plants (tops and roots) are killed by freezing, he said.

The system’s communications are sent at three status levels - advisory, watch and warning. These are assigned by geographic area, so different parts of the state or region are often not under the same level. Status can change and may be upgraded to a higher disease probability, downgraded or canceled.

Advisory status carries the lowest level of urgency and lowest potential for disease developing in the short term. Watch is used when conditions are conducive for blue mold development, but usually before blue mold has become active in an area. Warning is issued once blue mold activity has been confirmed in an area, and it remains in effect as long as conditions remain favorable for continued spread and development of the disease.

“Our purpose is to provide growers with key pieces of information in a timely manner that they can then use in their decision-making,” Nesmith said.

Keys to controlling blue mold include delaying arrival and disease buildup by preventing over-wintering locally, using blue-mold-free transplants, reducing disease-conducive environments, reducing plant susceptibility and providing proper fungicide applications.

The worst epidemic in Kentucky occurred in 1996 when growers sustained an estimated $190 million loss due to the disease, he said. Last year, there was also a severe blue mold outbreak causing damage in 100 of the state’s 120 counties.

Blue mold is an important disease because of the direct losses it can cause, the high control costs and its ability to impact export opportunities. For example, the trade agreement with China requires that all counties with blue mold be reported as it occurs and that samples of blue mold be submitted from each county or marketing area to the appropriate U.S. Department of Agriculture’s Animal and Plant Health Inspection Service for examination. County Extension agents play a major role in getting this accomplished.

“ China and most of the export world monitor the system,” he said. “In a modern-day world, having a system that is transparent is a valuable tool in the export system.”

The warning system incorporates and serves in a cooperative network with local and national blue mold advisory and control efforts. Locally, it is connected directly to each county Extension office, UK Agricultural Weather Center, Kentucky Pest News, and Kentucky's agricultural media.

For this system to function properly, it is very important that local Extension offices keep the warning system and diagnostic laboratories apprized of current blue mold situations in their counties.

“When making forecasts, critical data is what’s happening on the ground,” he said. “We need the facts; missing data and invalid reports are very damaging to the system.”

Nationally, it cooperates closely with the North American Plant Disease Forecast System, headquartered at North Carolina State University , which prepares "Blue Mold Forecast."  The national forecasts and reports are of great value in preparing the status reports, Nesmith said.

The process used to determine where the spores go from known sources is similar to predicting where smoke goes and settles down from a fire. Knowing where the “blue fire” is and valid weather data are critical assets in the analysis.

“Once we have an assumption as to where these spores are going, then, we have to predict if they remained alive during the trip or if environmental conditions killed them en route.”

Nesmith said then, it has to be determined if the condition on tobacco leaves will be conducive for infection and other aspects of the disease to occur. These latter factors are greatly impacted by farming practices, growth state, field conditions and weather.

All this data is used to establish the warning status and give farmers the ability to interrupt the disease’s spread along the process by management decisions.

“We urge the regular following of the Kentucky Blue Mold Warning System for guidelines and education related to the situation in Kentucky , because this information is time sensitive,” he said.

The reports not only serve Kentucky growers but are intended to directly serve burley and dark tobacco producers in southern Indiana , southern Ohio , West Virginia and Missouri , plus transplant producers supplying Kentucky and the region located in Tennessee , North Carolina , South Carolina , Florida , Georgia , Virginia and Michigan.

Anyone interested in subscribing to the system can do so by going to the Kentucky Blue Mold Warning System web site at www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm. Information at the bottom of the site tells you how to subscribe to the e-mail alerts.

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Contact: 

Editor: Laura Skillman 270-365-7541 ext. 278
Source: William Nesmith, 859-257-7445 ext. 80721