Fungal disease forecasts available

In his 25 years of teaching plant epidemiology at North Carolina State University, Charlie Main had two burrs under his side, so to speak. Soybean farmers in the United States this year will likely be glad he found a solution to the academic thorns in the flesh that he faced.

Teaching about the dynamics of disease epidemics led him to develop economic thresholds to learn of the impact of diseases, and eventually to a forecasting system that gives growers and industry at least 48 hours advance warning of a possible epidemic of fungal diseases such as Asian soybean rust. “We got involved with thresholds largely because I couldn't find any good information as a teaching source.”

The other thing that bothered him? “We had all this information, but it was piecemeal,” the semi-retired, white-bearded Main says. “Unless you heard one of our good county agents or Extension personnel lay this out for you, you just got bits and pieces from different sources and you had to put it together for yourself and it's rather complex.”

That practical theory is what's behind the North American Plant Disease Forecast Center: Bringing information together in one place regarding the spread of disease to the North American hemisphere.

Now in its tenth year, the center is heading up the forecasting for Asian Soybean Rust in the United States. It's found on the Web at

It began as a forecast for blue mold in tobacco and now includes cucurbit downy mildew and Asian soybean rust for the entire North American continent. In addition, the forecasting center has done work on bio-terrorism

In 1995, a blue mold epidemic had the tobacco industry in a panic. “We were contacted by our administrators and asked to put together a forecasting model for tobacco blue mold,” Main says.

That first year, Main and his colleagues, including Meteorologist Thomas Keever, “cut and pasted” forecasts and trajectories, detailing where tobacco blue mold would likely hit. They had a system in place within two weeks.

Since 1996, the NAPDFC site has been online. Last year, the site recorded more than 400,000 hits for blue mold alone. “That's a pretty good indication that a lot of people are following this, if you consider that a Web site that deals with tobacco isn't quite as popular as a lot of the Web sites out there.”

In the early years of the NAPDFC forecasts, many feed and seed stores would download the information and post it on bulletin boards for farmers to use. A toll-free number will also list the forecasts and provide a risk analysis of fungal diseases.

“Many times, telling people they're at low risk of moderate risk is just as valuable as telling them they're at high risk,” Main says.

Main believes the forecasts help farmers make better decisions on when and how much chemical to spray. “Economically, it saves him money and saves the environment. With tobacco, it's a high-cash crop, so farmers can really put a number of applications of fungicides and still receive benefit from it.

“With soybeans, it may be a different story,” Main says. “Two or three applications at the most and they will need to be put on at the right time and the right frequency.” The Asian Soybean Rust site will contain the recommended fungicides, as well as the rates and recommended spray equipment to use.

“The reason for the science of plant pathology is to deal with plant diseases and to find methods to manage them,” Main says. “We used to call it control, but management is probably a better concept.”

The spread of these diseases is called epidemics. “In human medicine, we have the CDC that forecasts and deals with human epidemics,” Main says. “We deal with plant disease epidemics. Each one of these pathogens and hosts has different dynamics. The study of this is called epidemiology.”

Disease management infers some kind of action to reduce the impact of the disease and “make it economically feasible to grow the crop,” Main says. “When you have things that blow around through the air, it rapidly becomes a community disease. You might have 95 percent of the growers in a county that are practicing good control measures and you might have one farmer right in the middle who doesn't use any control measure. He can provide a source of spores and make the others less effective in their disease management.

“How a farmer perceives his losses” largely determines how he looks at the risk of disease to his business, Main says.

Making the farmer aware of those risks is the first important step toward helping him determine a course of action, Main says. “We're essentially an Extension product. We're taking information and making it available in real time to growers to help them make decisions that largely rely on timing.”

e-mail: [email protected]

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