On Aug. 2nd soybean rust (SBR) was detected in a soybean sentinel plot in DeKalb County, Alabama, in the northeast corner of the state. Less than 1% of the plants had visible symptoms.
The detection of SBR was on a maturity group III variety at growth stage R5 (beginning seed), with 80% canopy closure. This is the earliest SBR has been detected in DeKalb County by approximately 4 weeks. Crossville, Alabama where the sentinel plot is located is about 75 miles southwest of Chattanooga, Tennessee. In general, SBR appears to be advancing more rapidly into central Alabama then in previous years. Producers with later planted soybeans need to be aware of this situation and plan accordingly.
Soybean sentinel plots located in Tennessee have been scouted over that past weeks and no SBR has been observed. These plots and additional sites will be monitored for SBR and other soybean diseases. Updates on the presence of SBR will be posted to the Integrated Pest Management – Pest Information Platform for Extension and Education (http://sbr.ipmpipe.org or http://sbrusa.net), the UTcrops.com news blog (https://news.utcrops.com), and the UT Rust Hot Line (1-877-875-2326).
It is possible, based on forecasted storm tracks, that SBR may move into southeastern Tennessee and perhaps the Carolinas. Fungicides effective against soybean rust and other soybean diseases can be found at UTcrops.com under Soybean Diseases and Nematodes – Fungicide Table – 2013 (developed by the North Central Regional Committee on Soybean Diseases and the Regional Committee for Soybean Rust Pathology).
Pathogens that have been reported in some soybean fields in Tennessee include downy mildew and Frogeye Leaf Spot (FLS). Downy mildew rarely reduces yield and hence fungicides are not recommended for its control (more information on downy mildew at: http://www.planthealth.info/downymildew_basics.htm). On the other hand, FLS can cause significant yield loss in susceptible varieties and is of increased concern with fungicide resistant strains (resistant to strobilurin or quinone outside inhibitor/QoI fungicide group) confirmed in 8 states. Free testing of FLS is being conducting this year at the West Tennessee Research and Education Center to determine if the disease is caused by Strobilurin/QoI fungicide resistant strains (see previous article for more information: Scouting and Sampling Frogeye Leaf Spot in Soybean, funding provided by the Tennessee Soybean Promotion Board). Information on other soybean diseases and fungicide decisions can be found in the previous article: Scouting for Soybean Diseases and Deciding on Fungicides and Application Timing. If you have any questions about soybean diseases or management options contact your local county extension agent or myself at 731-425-4713 (youngkelly@utk.edu).
