U.S. Scientists on Watch for Potentially Devastating Soybean Disease

            Auburn, May 23, 2003 -- U.S. scientists are keeping a watchful eye on the progressive spread of soybean rust.  Soybean rust is a harmful new soybean plant disease that originated in the Eastern Hemisphere.  But it has made its way west and has been discovered in South America.

            A plant pathologist with the Alabama Cooperative Extension System said the disease was found in Brazil and Paraguay in 2002.

            Dr. Ed Sikora said the disease could be a significant problem if it becomes widespread in the United States.

            “This is a devastating plant disease. Yield losses of up to 80 percent have already been reported in parts of Asia and Africa,” said Sikora. 

            Soybean rust is a fungal disease that is dispersed when rust spores are spread by wind.  Because spores travel on wind currents, Sikora said it’s probably only a matter of time before the disease migrates out of South America into central America and then into the continental United States.

            If soybean rust enters the United States, a USDA risk assessment by computer simulation shows this disease could cause yield losses of up to 40 percent in major U.S. production regions.

            Yield losses caused by soybean rust depend on the severity of infection. Under severe conditions, rust lesions will cover most of the leaf area and cause premature defoliation.  Heavily infected plants also have fewer pods and lighter seeds, which can lead to significantly less marketable yields.

            “While soybeans aren’t as big a crop in Alabama as cotton and corn, the disease is still a threat,” said Sikora.  “Farmers cannot afford to lose large portions of their crop to disease.”

            About 150,000 acres of soybeans will be planted in 2003, according to the Alabama Agricultural Statistics Service.  That is down from 2002 when about 170,000 acres were planted and down significantly from the five-year average planting of more than 215,000 acres.  The 2002 crop was valued at almost $20 million.

            In contrast, the state statistics service expects 580,000 acres of cotton and 220,000 acres of corn to be planted this year.

            Sikora added that extensive research is under way across the United States and internationally to develop ways to combat the disease as well as to develop rust-resistant soybean varieties.

            “Probably the farmers first line of defense against soybean rust will be effective management practices, including timely fungicide applications,” said Sikora.  “But research may show the need to alter some cultivation practices, such as irrigation.”

            Moisture is essential for rust spore germination, so there is concern that irrigated fields might be more susceptible to soybean rust.

            “The second line of defense against this disease will be the development of resistant varieties,” added Sikora. 

            Research has already shown that a number of popular soybean varieties in the United States are susceptible to the disease.  But research is also beginning to identify some varieties that exhibit some degree of resistance to soybean rust.         

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