The Asian soybean rust, Phakopsora pachyrhizi, has been known to drastically reduce yields. In areas where the pathogen occurs commonly, yield losses up to 80% have been reported. The pathogen has been limited to the Eastern hemisphere until it was found in Hawaii in 1994 and the United States in 2004. The distribution of P. pachyrhizi includes Africa, Asia, Australia, South America, and North American. The rapid spread of P. pachyrhizi and potential for severe yield losses makes this the most destructive foliar disease of soybean. As soybean rust continues to infect soybean in the U.S., it could have a major impact on both total soybean production and production costs.