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,
Stem rust the end of the growing season black telia are produced. For this reason stem rust is also known as 'black rust'. The telia are firmly attached to the plant tissue. The site of infection is a visible symptom of the disease. Pycnia appear on barberry plants in the spring, usually in the upper leaf surfaces. They are often in small clusters and exude pycniospores in a sticky honeydew. Five to ten days later, cup-shaped structures filled with orange-yellow, powdery aeciospores break through the lower leaf surface. The aecial cups are yellow and sometimes elongate to extend up to 5 mm