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Soybean Plant Health

Asian Soybean Rust

Asian Soybean Rust

Asian soybean rust is an aggressive foliar disease caused by the fungus Phakopsora pachyrhizi. The disease is most destructive in the tropical and subtropical regions of Asia and Australia. In the past decade it has spread to several countries in Africa and in 2001 was found in South America. Soybean rust was confirmed in the continental United States in November 2004.

The name Asian soybean rust is used to distinguish the soybean rust disease caused by Phakopsora pachyrhizi from a mild form of soybean rust, Phakopsora meibomiae, which is endemic to the Caribbean region. Phakopsora pachyrhizi is the more aggressive of the two species and causes more damage to soybeans. Molecular diagnostic techniques are used to distinguish the two fungi.

Rust spores, called urediniospores, are able to penetrate the plant cells directly, rather than through natural openings or through wounds in the leaf tissue. Thus infection is relatively quick:  about 9-10 days from initial infection to the next cycle of spore production.

Backlighting can help detect initial symptoms of rust.

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