Asian Soybean Rust - Management

Rust-resistant Soybean Varieties

Planting resistant varieties has been very successful in managing rust diseases of wheat and corn, and is expected to be an effective, long-term solution for soybean rust as well. Much of the groundwork has been done, but best estimates say that resistant commercial soybean varieties are still several years away.

Soybean breeders and plant pathologists are now in their third year of field-testing resistant soybean germplasm in the U.S. In 2007, 703 soybean lines were evaluated in seven different locations and researchers reported a clear sorting of resistant reactions compared to susceptible soybean varieties. Several genes for resistance have been identified and named. The next step is to make the selections, and to cross the resistant germplasm with "elite parents"—- soybean varieties with the desired agronomic characteristics.

Check the USDA PIPE rust maps frequently. Click on your state to read current advisories.

Foliar Fungicides

In the meantime, proper application of an appropriate fungicide at the earliest time possible after rust is detected has been shown to effectively manage rust. There are several factors to consider in making spray decisions to manage soybean rust. Generally, fungicide programs should not be deployed until the risk of infection is high. A nationwide, real-time monitoring and forecasting system is in place. Use that system to guide spray decisions.

Timing and coverage of the low and mid-canopy are important factors for success. Read the recently -updated reference guide Using Foliar Fungicides to Manage Soybean Rust for more details.

Fungcides registered for soybean

Table 1 lists the fungicides currently registered in the U.S. for soybeans (Section 3 labels). In addition to those products listed, several fungicides that received Section 18 labels for soybean rust in 2005 were recently granted Section 3 labels for use on soybean. Check with your state agricultural Extension service for the latest information on specific products labeled in your state.

Section 18 Emergency Exception Registrations

Since 2005, additional fungicides were made available through Section 18 Emergency Exemption registrations. This was a situation in which the U.S. EPA allowed limited use, during a crisis situation, of fungicides that do not have established food tolerances. Although approved for use, it must be remembered that Section 18 fungicides can legally be used only for soybean rust on soybean. As a result, each state determined what event triggers an acceptable use of Section 18 soybean rust fungicides.

While some of these products have since been approved for a Section 3 label, indicating that EPA has approved their use throughout the U.S., others have not, and their Section 18 labels have expired as of November 10, 2007. Check with your state agricultural Extension service for the specific products labeled in your state.

Table 1. Fungicides available for use on soybean to manage Asian soybean rust (Section 3 labels).

Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.