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44734

Asian soybean rust detected in South Carolina

Asian soybean rust has been found in sentinel-plot soybeans in Calhoun County, S.C., according to www.stopsoybeanrust.com.

This is the first rust in the state this year and the farthest north rust has been found in the U.S. in 2006. There are now 35 counties in seven states that have had rust in 2006.

On www.sbrusa.net and in a more detailed South Carolina Soybean Rust Note e-mail to soybean specialists, South Carolina officials led by John Mueller, Clemson University Extension soybean pathologist, reported the case.

"Asian soybean rust was identified in samples collected last Thursday (Aug. 17) in Calhoun County from a field of Maturity Group V soybeans located near the intersection of State Road 22 and Interstate 26. This is the first identification of rust in South Carolina during the 2006 growing season," Mueller said.

"The plants were in a sentinel plot and were at growth stage R-5 (full size pods containing developing beans). Out of the 25 leaves examined, only one leaf exhibited rust. On that leaf was a lesion less than one-fourth inch in diameter which contained three very young pustules that had just begun sporulating. Immediately adjacent to this sentinel plot of MG V soybeans was a sentinel plot of MG IV soybeans," Mueller continued. "No rust was detected on the 25 leaves examined from that plot. The MG V plot exhibited very lush growth -- 40+ inches tall in 38-inch rows."

Mueller made the following fungicide recommendations:

"At this time the levels of rust in South Carolina appear to be extremely low," he said. "However, environmental conditions are favorable for rust and other diseases to develop. An application of a strobilurin to provide protection against rust and to help control other diseases is a good option for the next week. This is especially true for soybeans with a high yield potential that are between growth stages R3 and R5. At this time these soybeans show the highest potential for return from a fungicide application.

"To control diseases in addition to rust, you must use a strobilurin or a combination product containing a strobilurin," he added.

Now that rust has been found in South Carolina, albeit at a very low incidence, scouting of individual fields may be warranted, the state commentary said. "However, the best indicator of rust in your area is still the nearest sentinel plot to your field."

The following South Carolina counties were sampled last week: Aiken, Allendale, Anderson, Bamberg, Barnwell, Calhoun, Colleton, Darlington, Florence, Hampton, Horry, Lee, Orangeburg, Sumter and Williamsburg.

Alabama and USDA officials said rust no longer visible in Montgomery County.

"Soybean rust can no longer be found on kudzu in the city of Montgomery. The disease had previously been detected on five kudzu patches in the downtown area where it had successfully overwintered," according to USDA commentary. "These patches have been monitored on a biweekly basis since they were first discovered in January. The disease has not been detected at these kudzu sites since early June. Central Alabama has experienced a severe drought for most of the growing season which likely had a direct impact on the pathogens ability to survive."

Asian soybean rust has been found in sentinel-plot soybeans in Calhoun County, S.C., according to www.stopsoybeanrust.com.

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