2.9 Soybean Rust

Asian soybean rust (Phakopsora pachyrhi) is a plant disease that is currently found in Australia, Africa, Asia, and South America. Soybean rust is an airborne fungal disease that can cause premature defoliation, which results in fewer pods, lighter seeds and poor seed quality. Rust damaged crops can suffer up to an 80 percent yield loss. Soybean rust can be easily confused with other common soybean diseases such as bacterial pustule, bacterial blight or septoria brown spot. Soybean rust and the seed from rust infected plants are not shown to be harmful to humans or animals.

Soybean rust can be transferred many ways but most commonly it is transported by wind/air currents. Airborne spores can be carried for long distances and can infect and reproduce on numerous alternate host plants, including kudzu, which grows in many areas of the southeastern United States. Soybean rust will be impossible to contain and eradicate in the continental United States, because the spores are produced in massive quantities on a variety of infected plants, and then dispersed via air currents. Spores may also be transmitted on infected plant material or on articles such as shoes and clothing.

Asian soybean rust has been detected in at least eight states since its initial discovery in a research plot in Louisiana on November 6, 2004. As predictive modeling indicated, soybean rust spores were introduced via hurricane activity, moving into the United States from the Southern Caribbean.

In the foreseeable future, the only way to control the disease is through timely fungicide applications and management plan development. Currently there are two fungicides registered for foliar application in the United States. Several other fungicides and application programs are being evaluated and an application for Section 18 status has been submitted to the EPA. Researchers continue to work to develop genetically resistant or tolerant varieties to be used as an alternative or in conjunction with fungicide applications. In addition, seed treatment options are being explored for possible effectiveness and efficacy.


  • Minimize Spread
    Last updated: September 20, 2011

    NASDA believes communication among government agencies as well as within the farm community is central to monitoring and minimizing the damage from soybean rust. NASDA supports producer education about identification of the disease and about viable options to control the pest, so producers are well informed and equipped to address the problem.

    Quarantine and eradication steps are not practical as the disease may infect many plant species (crop and non crop) found in the United States. Therefore, it is imperative that NASDA members, USDA and other federal officials coordinate their actions and quickly inform producers of a rust confirmation. Time is of the essence as under the right conditions, soybean rust may produce spores at an alarming rate, further infecting additional fields. The faster the news of a rust confirmation can be communicated with growers, the earlier the producers can apply fungicides to lessen the consequences of a soybean rust infestation.

    Farmers must be assured that communication concerning infected fields with agricultural officials will not result in punitive actions. Rather, it must be emphasized that early detection allows officials to warn growers so that both protective and curative fungicide treatments can begin as soon as possible.

    NASDA encourages the USDA to take a leadership role in the development of a soybean rust monitoring plan to determine the seasonal rate of spread. Further, the USDA should take the lead in the development of a soybean rust management plan.

  • Homeland Security Designation
    Last updated: September 20, 2011

    NASDA urges the USDA and DHS to swiftly re-evaluate the pathogens currently on the Select Agents List. NASDA strongly urges the evaluation to disregard pathogens that are predicted to naturally spread to the United States, as rust is a prime example of a pathogen with no control mechanism to stop the airborne spread.

    This Select Agent designation highlights soybean rust in an unnecessarily negative manner. Soybean rust should be treated as any other normal quarantinable pest that could enter the country at any time. As long as soybean rust is labeled a Select Agent, we raise the risk that trading partners could use rust as reason to block imports of U.S. soybeans.