Asian soybean rust, a crop-killing disease first detected in the United States last fall, has been found near Citra on soybeans at a University of Florida “sentinel plot” planted early to detect the fungus. It was one of two findings this week that mark the first appearances of soybean rust on U.S. soybeans during the typical growing season, and UF researchers fear the discovery signals the beginning of outbreaks that may devastate the nation’s $16 billion soybean industry. 

The disease was found Wednesday by Jim Walker, a biological scientist with the Florida Department of Agriculture and Consumer Services, Division of Plant Industry, which has been monitoring the plots in cooperation with UF’s Institute of Food and Agricultural Sciences, or UF/IFAS. On Thursday, a Division of Plant Industry laboratory confirmed that the pathogen was Asian soybean rust, said David Wright, a UF/IFAS professor of agronomy in Quincy.

The other discovery was made Tuesday on a sentinel plot in Baldwin County, Ala., Wright said. Previously, soybean rust was found in Florida and other Southern states after the 2004 growing season ended. The crop is typically planted in the spring and produces soybeans in the summer and early fall.

“There’s a lot at stake now, and nobody really knows what will happen,” Wright said. “But if there are major problems, it will affect a lot of people.”

Losses from the disease - which kills up to 95 percent of infected plants - could drive up prices on products ranging from margarine and peanut butter to livestock feed and biodiesel fuel, he said.

UF and state agricultural experts have joined a nationwide effort to help farmers protect this year’s crop, estimated at 74 million acres, Wright said. Soybeans are grown in 31 states, with heaviest production in the Midwest.

By monitoring sentinel plots at 26 Florida sites, Wright and other scientists at UF’s North Florida Research and Education Center in Quincy hope to provide data on the disease’s development, distribution and other factors that could assist farmers in northern areas of the nation, Wright said. The project is funded by the U.S. Department of Agriculture and the North Central Soybean Research Program, a consortium representing higher education institutions in the 31 soybean-producing U.S. states.

Many growers are concerned about being caught off guard by soybean rust, because the fungus, known as Phakopsora pachyrhizi, is spread by tiny spores that can travel hundreds of miles on air currents, he said.

“The fungus also matures very quickly,” Wright said. “Once a spore lands on a host plant it can produce new spores in nine days.”

Despite its name, soybean rust attacks more than 30 species of legumes, a plant family that includes beans, peas and clover, he said. On soybeans, it causes infected leaves to develop small brownish spots, then turn yellow and fall off.

Crop protection sprays called fungicides control the disease in South America, where soybean rust arrived in 2001, Wright said. But U.S. farmers fear the sprays could cut profits.

Fungicide treatments for an acre of soybeans would cost $10 to $30 per year, he said. Protecting the entire U.S. crop could total more than $1 billion.

“Soybeans have a low profit margin, probably $25 to $50 per acre,” Wright said. “So there’s not much room for new expenses.”

To determine which fungicides work best under Florida’s growing conditions, UF researchers are conducting field trials of about 20 products, said Jim Marois, a UF plant pathologist. The trials, held at the Quincy center, will also investigate application methods.

“Growers prefer the lowest-priced products that work,” Marois said. “We want to help them make informed choices.”

UF researchers will also investigate tilling methods that bury old plant residue, a practice that could prevent dormant spores from starting new outbreaks, he said.

“This method will only work against spores that survive the winter here, and we’re not sure that will happen,” Marois said. “We hope not, because then we’ll only have outbreaks if spores arrive from other countries.”

Native to Asia, soybean rust is believed to have reached the United States in September when winds from Hurricane Ivan transported spores from South America, he said. There, the disease affects Brazil, Bolivia and Paraguay.

Concerns about international terrorism spurred U.S. preparations for soybean rust, Marois said. In the aftermath of the Sept. 11 disaster, it was identified as a possible bioterrorism agent, which led to the development of federal programs to identify and respond to the disease.

“We’ve had a very coordinated effort,” Marois said. “Although nobody’s happy soybean rust is here, the silver lining is that we’re learning more about how we can take a nationwide approach to crop diseases.”

Florida will be a critical state in the fight against soybean rust, said X.B. Yang, a professor of plant pathology at Iowa State University in Ames.

“What happens in Florida may well determine the risk level for Midwest states,” said Yang, who is part of an Iowa group collaborating with UF researchers. “Information generated by UF scientists is essential for colleagues in the north.”