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Soybean Production in Mississippi

Asian Soybean Rust

Leaf with rust Click to enlarge Asian or Australasian soybean rust (SBR) has been a problem in many parts of the world since 1902 when it was first identified in Japan. Since that time, many countries on many continents have been affected by this disease.

Between 1997 and 2001, South Africa, Uganda, and Zimbabwe confirmed the presence of SBR. By 2000, rust had spread all the way to Paraguay, South America and later into other adjacent countries including Argentina and Brazil, and in 2004 SBR was identified in nearby Bolivia.

In the fall of 2004, SBR was positively identified in several commercial soybean fields along the Mississippi River. Other states that discovered rust included Alabama, Florida, Georgia, Louisiana (the first place found in the continental US, November 10, 2004), Missouri, South Carolina, and Tennessee (1Figure 1).

The disease is thought to have arrived in the United States on wind currents associated with Hurricane Ivan which occurred in September 2004. The locations that the pathogen was identified along with the pattern that Ivan traveled suggest that the spores came in from South America on the hurricane winds.

Soybean leaf with rust The major impact that SBR has on soybean production is reducing YIELD! Protecting yield is the number one concern for soybean producers. Rust has shown to affect yield tremendously. Yield loss as high as 100 percent has been observed in some countries. However, yield loss estimates applied to the U.S. soybean crop based on losses from other countries has produced what appears to be inflated estimates since major yield losses have not occurred on a widespread scale in the U.S. to date.

With that said, 2009 marked the first year when a yield reduction was recorded that could be attributed to SBR in Mississippi. Two fields in Noxubee County, near Brooksville, recorded a yield reduction of between 8 and 25 percent. Neighbors in the area that applied a fungicide at the R3/R4 growth stage, while reporting a minimal yield reduction, did not suffer as much damage as those producers that did not apply a fungicide. However, refer to the Mississippi State University Extension Suggestions for the proper use of a fungicide in the event of infection due to SBR as well as the specific suggestions regarding the R3/R4 treatment timing.

Presently, resistant soybean varieties are not available and cultural practices have not been determined to have an impact on preventing yield loss from SBR. The only option available to producers is the use of fungicides (see Control page with the labeled fungicides available for use in MS). Fungicides have proven to be beneficial in other countries.

Pictures and slides in this subject area have been shared commonly among plant pathologists, soybean agronomists, and many others dealing with SBR. They are courtesy of APHIS, USDA-ARS (Dr. Monte Miles, Dr. Glen Hartmen), EMBRAPA, a private consultant in Zimbabwe, BASF Chemical Co., and Syngenta.

1Courtesy of Thomas Weissling and Loren Giesler, University of Nebraksa-Lincoln. Used with permission.