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Asian Soybean Rust: Background and Issues

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Publication Date: January 2005

Publisher(s): Library of Congress. Congressional Research Service

Series: RL32225

Topic: Agriculture, forestry and fishing (Crop management)


On November 9, 2004, Asian soybean rust (ASR) was discovered in the United States in an experimental field in Louisiana. In the following three weeks, it was discovered in eight additional southern states -- Alabama, Arkansas, Florida, Georgia, Mississippi, Missouri, South Carolina, and Tennessee. Because ASR's arrival in the United States came late in the crop year, it is not thought to have had any measurable effect on 2004 soybean production. Furthermore, its detection has provided an early warning and has given the U.S. soybean sector time to prepare strategies to guard against possible ASR damage to the 2005 soybean crop.

ASR is a harmful fungal disease that affects the growth of several commercial plants, most notably soybeans. The rust spores, once windborne, 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 disease's rapid transmission rate coupled with an abundance of host species suggests that eradication would be unlikely once the fungus is established in the United States. As a result, the most effective treatment is thought to be the development and use of resistant plant 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.

Three chemicals are presently registered with the U.S. Environmental Protection Agency (EPA) for treatment of rust on soybeans. In addition, EPA has approved several temporary emergency exemptions (under Section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act) for additional fungicides. Estimates suggest that the U.S. currently has fungicide capacity to treat up to 12 million acres. During the past three years (2002-2004), U.S. soybean plantings have averaged 74.2 million acres. Thus, available fungicide appears sufficient to treat about 16% of average plantings. A shortage of fungicides could lead to a constituent call for congressional action.

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. 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 2004 USDA study suggests that annual U.S. economic losses could range between $240 million and $2 billion, depending on the severity and extent of any outbreaks.

The arrival of ASR has implications for several public policies including pest control research (particularly the development of resistant varieties), pesticide regulation, disaster assistance, and crop insurance. This report will be updated as events warrant.