Soybean rust was detected on 1 leaflet out of 20 collected from a soybean field on the Milan Research and Education Center.  The infected leaflet had approximately 20 sporulating pustules.  No fungicide was applied to the soybeans and the sample was collected from a low lying spot of the field where soybean rust has been reported in previous years.  The soybeans are in reproductive growth stage R6 – R7. Samples from soybean sentinel plots across the state are being examined to determine any other areas with soybean rust infections.

While this is the first report of soybean rust in Tennessee most soybeans have already reached the “R5” reproductive growth stage (seed 1/8 inch long in any pod on any of the top 4 nodes) and will probably not observe an effect on yield if soybean rust developed over the next few weeks. We are not recommending spraying for soybean rust at this time but producers should report any possible rust infections to their County Agent.  The national rust web site (www.sbrusa.net) is the best place to check on where soybean rust has been found or just call the UT Rust Hot Line (1-877-875-2326) any time for a free one minute update. Your local county Extension leader will also be able to help you identify soybean rust.

As previously stated in the ‘Soybean Rust Update’ on August 28, producers who have already sprayed a fungicide (Triazole or a mixture of Triazole + Strobilurin) for other diseases may still have some protection from rust infection if it has not been over 2 or 3 weeks since they sprayed.  Recommendations to spray a Triazole or Triazole + Strobilurin fungicide would only be made if weather conditions remain favorable for rust, soybeans are able to produce a potential yield of at least 30 bushels/acre and are still in a growth stage between R1 and R5.  Again most soybeans are already passed this stage and will probably not be harmed by a rust infection this late in the growing season.