Soybean Rust |
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Background
Soybean rust is a serious disease causing crop losses in other parts of the world. The purpose of this web site is to give background and identification information on soybean rust. Included on this web site is information on how the fungus might be first detected on soybean plants, other soybean rust hosts that occur in the United States, the characteristics of soybean rust for proper identification, and procedures for identification verification.
This site includes a Soybean Rust Data Sheet (PDF; 190 Kb) developed by USDA, APHIS, Plant Protection and Quarantine, which gives baseline information on what is known about the disease with references for further investigations.
Distribution: Soybean rust is caused by two fungal species, Phakopsora pachyrhizi and Phakopsora meibomiae. It has been reported in various countries including Australia, China, Korea, India, Japan, Nepal, Taiwan, Thailand, the Philippines, Mozambique, Nigeria, Rwanda, Uganda, Zimbabwe, South Africa, Brazil, Argentina, and Paraguay. The first detection of soybean rust in the United States was P. meibomiae reported in Puerto Rico in 1976 and this species has proven to be a weak pathogen. Phakopsora pachyrhizi, which is much more aggressive, was reported in Hawaii in 1995. Recent introductions of P. pachyrhizi in other parts of the world show a rapid spread causing severe damage in Zimbabwe, South Africa, Paraguay, and Brazil. Yield losses have been reported from 10-80%.
Hosts: A complicating factor for pest detection and control are the large number of legume hosts that can harbor soybean rust. In addition to soybean, there are 30 species in 17 genera of legumes reported to be hosts for soybean rust in nature, with 60 species in 26 genera that were successfully inoculated under laboratory conditions. One widespread host in the United States is kudzu, Pueraria montana var. lobata, that could serve as a reservoir for soybean rust. There are a variety of other important hosts that are leguminous crops or weeds that have shown varying degrees of susceptibility to both species of Soybean rust. Some other common hosts are yellow sweet clover (Melilotus officinalis), vetch (Vicia dasycarpa), medic (Medicago arborea), lupine (Lupinus hirsutus), green and kidney bean (Phaseolus vulgaris), lima and butter bean (Phaseolus lunatus), and cowpea or backeyed pea (Vigna unguiculata). See the Soybean Rust Data Sheet (PDF; 190 Kb) for a more complete list of hosts.