SOUTH CAROLINA SOYBEAN RUST UPDATE
7 September 2015
FROM: John Mueller, Extension Soybean Pathologist, Edisto Research and Education Center
As of today Soybean Rust has not been found in South Carolina
As most of you know last year was a very light year for Soybean Rust in South Carolina. Soybean rust was found in only one field very late in the growing season. The field happened to be in Bamberg County.
Based on observations from our colleagues across the Southeast, this year Soybean Rust is again spreading at a very slow rate. On August 21 Soybean Rust was reported to be in soybean fields in 5 counties in Mississippi. More important to us Soybean Rust was found in Decatur County, Georgia last week. Decatur County borders Florida just a little west of Tallahassee. This is the closest find on soybean to South Carolina.
Our weather is now a little cooler and a lot cloudier and wetter with dews extending later into the day. These are good conditions for rust to develop. Now the inoculum must blow in from somewhere, most likely the Georgia/Florida line.
In the past we have not found Soybean Rust in any field prior to that field flowering. If we find rust at very low levels we have at least 7 to 10 days to spray. We cannot spray a fungicide after a field reaches R-6.
If you want to scout for rust in your fields you need to collect at least 50 leaves and examine the underside for pustules. If you think you have pustules please take the sample to your county agent for confirmation. It is easy to mistake many abnormalities for rust pustules or symptoms.
If you want to spray to protect your soybeans from all of the other diseases that can occur that is fine. However, until we actually see rust a lot closer to South Carolina I would not make a fungicide spray aimed solely at soybean rust.
As in the past if you are interested the current status of rust in the continental US can be found anytime at http://sbr.ipmpipe.org.