Soybean rust has been found in the Giles County soybean sentinel plot at very low level – 1 leaflet out of 37 had approximately 20 sporulating pustules. All other sentinel plots are still negative for soybean rust.
Leaves collected from soybeans at growth stage R6 (full seed) in the Giles County sentinel plot were collected on Sept. 10th and incubated for 3 days. The field is approximately 1 mile north of the Tennessee/Alabama border. Below are images of the 1 leaflet with soybean rust pustules that have sporulated. Arrows are pointing to areas where pustules are located, 3 areas are within circles drawn on the leaflet. The yellow arrow is pointed to the area that is magnified in the second image below. While the leaflet is older and there are other types of lesions on it, soybean rust severity is only 1% based on the area affected.
While this first report of soybean rust in Tennessee is earlier than in previous years most soybeans are past the point of spraying a fungicide (R6/full seed and later). Also applying a fungicide now could be a lost investment on later planted soybeans or soybean behind wheat that are still in the window for fungicide application (R3/beginning pod to R5/beginning seed) due to an early freeze robbing yield. Feel free to contact your local county agent or myself if you have any questions about your specific situation and fungicide options.
Sentinel soybean leaves will continue to be examined from across middle and west Tennessee for soybean rust. Any positive observation will be reported here on news.utcrops.com, the sbrusa.net website, and the UT Rust Hot Line (1-877-875-2326).
