Soybean rust is here

By Tracy Outlaw

Soybean rustOver the past several years, American farmers have watched the spread of soybean rust from its origin in Asia to Australia, Africa and South America.  It was first recorded in Japan in 1902. It was first detected in the United States through Louisiana on November 10, 2004, and was identified in South Carolina on December 1.  Fortunately, soybean rust arrived too late in the season to cause much damage to the U.S. crop. But this year’s crop is at higher risk.
   
Clemson Extension and regulatory personnel began meeting with South Carolina growers in January. Soybean rust is caused by a fungus, Phakospora pachyrhizi.  It is spread by wind-borne spores and can quickly infect an entire field of soybeans. In its native Asia and Australia, it causes periodic epidemics resulting in major crop losses. 
   
“Controlling rust is even more difficult because it also can infect more than 90 species of legumes, including kudzu,” said David Howle, assistant director of Clemson Regulatory Services. “Once it begins, this disease can move very quickly, with the potential to defoliate a field in two weeks.”
   
In cooperation with the U.S. Department of Agriculture and agencies in other states, Clemson will establish a network of monitoring plots to detect the return of soybean rust to South Carolina, and to provide growers with early warning of the need to spray fungicides.
   
Unfortunately, soybean rust is sometimes hard to identify. Early symptoms appear as yellowish mosaic discolorations on the upper surfaces of older leaves on the lower branches. As the disease progresses, infected leaves turn yellow, and brown or reddish lesions appear, generally on the bottom surface of the leaf. 
   
National updates will be provided weekly by the U.S. Animal and Plant Health Inspection Service (APHIS) website http://www.aphis.usda.gov/. For more information: Call the Clemson University Cooperative Extension Service in your county.