Asian soybean rust was first identified in 1902 in Japan. In 2004, the disease, which can reduce yield or even wipe out a field, was positively identified in the United States in several commercial soybean fields along the Mississippi River. Major yield losses have not yet occurred on a widespread scale in the U.S., where the first line of defense is a system of sentinel plots. To date, no soybean varieties are resistant to the disease, nor have specific cultural practices been identified to prevent yield loss. The only current option is fungicides, which have proven effective in other countries.