Asian Soybean Rust: Background and Issues
Randy Schnepf

Background

Asian soybean rust (ASR) is a harmful fungal disease that affects the growth of several commercial plants, most notably soybeans. The rust spores, once wind-borne, can spread rapidly and have been known to infect an entire region the same year the disease is first detected. ASR has reduced soybean yields by 10 to 80% in infected areas. The pathogen has been most destructive in Asia, Africa, Australia, and more recently South America. ASR is not known to occur in the continental United States; however, its arrival is expected within the next 3 to 7 years. The most likely mode of entry for ASR into the United States is expected to be airborne by wind currents of the upper atmosphere.

Controlling Rust

Because the pathogen can infect and reproduce on over ninety plant species, twenty of which are found in the United States, eradication is unlikely once the fungus becomes established. As a result, the most effective treatment is thought to be the development and use of resistant varieties. However, no commercial U.S. soybean cultivar is resistant to or tolerant of ASR. In the short term, the only effective responses are costly fungicides and the use of early maturing soybean cultivars. Two fungicides are presently registered with the U.S. Environmental Protection Agency (EPA) for control of rust on soybeans. However, independent efficacy data are still needed to confirm their effectiveness against ASR. Meanwhile two states are trying to obtain EPA Section 18 registrations (granting temporary emergency use rights) for fungicides presently in use against ASR overseas.

The U.S. Department of Agriculture (USDA) is coordinating a plan to deal with ASR that encompasses various USDA agencies, state land-grant universities, and industry participants. Despite USDA's preparation, concerns that ASR may be imported before the U.S. soybean sector has made adequate preparations have gained importance in recent months. This is due to market expectations that significant amounts of both soybeans and soymeal will have to be imported in 2004 to meet domestic needs, possibly from South American sources known to be infected with the rust. On Feb. 6, 2004, legislation (H.R. 3775) was introduced to ban imports of soybeans and soymeal from Argentina and Brazil. A senator has asked U.S. Agricultural Secretary Ann Veneman to impose a USDA ban on imports of Brazilian soybeans. However, USDA has dismissed the calls for a halt to soybean imports pending the results of a risk pest assessment being undertaken by USDA's Animal Plant and Health Inspection Service (APHIS) on the importation of bulk soybeans from countries known to be infected with ASR.

In the meantime, APHIS is seeking public comments on a draft document outlining the apparent risks associated with importing soybean products from countries affected by soybean rust. The APHIS Federal Register notice requesting public comments was published 12 March (F.R. Vol. 69, No. 49, p. 11831). Public comments are requested to be submitted by 12 April.

Potential Consequences of Rust Outbreak in U.S.

Widespread ASR infection in the United States would likely have significant regional and national effects on domestic and international commodity markets. Timely fungicide applications can prevent national yields from declining dramatically; however, the added cost of fungicides would likely lead to a significant reduction in soybean production in lower-yielding southern states. A ban on soybean and soymeal imports from South America also would likely produce regional effects, again where southern states would bear the brunt of market adjustments due to their growing livestock and poultry industries and strong regional feed demand, but supply deficit.

Resources

CRS Report RL32225, Asian Soybean Rust: Background and Issues

U.S. Dept. of Agriculture, Animal Plant Health Inspection Service, Plant Protection and Quarantine, Pest Alert: Soybean Rust, online information.

North Central Soybean Research Program (NCSRP), Plant Health Initiative, Soybean Rust, online information.

CRS Contact: Randy Schnepf (7-4277)

Page last updated March 28, 2004.

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