Soybean rust on the leaves of soybean plants and eventually kills the plants. The disease has caused serious yield loss of soybeans. In the areas where this disease is common, the yield losses can be up to 80%. In 2002, USDA reported 10-60% of yield losses in South America and Africa. Soybean rust is caused by two types of fungi, "Phakopsora pachyrhizi" and "Phakopsora meibomiae". It affects several important commercial plants, however, most notable for soybeans. Asian Soybean Rust can infect and reproduce on 90 known plant species, 20 of which are found in the United States, such as, soybeans, dry beans,
Soybean rust kidney beans, peas, leguminous forage crops such as trefoil and sweet clover and weeds such as kudzu. At the early stage of Asian Soybean Rust, it causes yellow mosaic discoloration on the upper surfaces of older foliage. At this stage, it is usually hard to identify since the symptoms are relatively small and poorly defined. Later as the disease continues to progress, the leaves will turn yellow and there will be lesions mostly on the undersides of the leaves and sometimes on petioles, stems or pods and premature defoliation can also be observed. Asian Soybean Rust produces two types of