Soybean Rust Sentinel Plot Monitoring and Fungicide Trial (as of July 10, 2006)

Missouri is participating in the Soybean Rust Sentinel Plot Program for the 2006 season. The 25 sentinel plots located throughout the state are being monitored by Extension Regional Agronomists and University Research Center personnel. Samples of 100 leaflets per plot were collected every other week through the vegetative stages of growth. As plants move into reproductive stages of growth sampling has been on a weekly basis. As of July 11, 2006, all samples submitted from the Missouri sentinel plots have been negative for soybean rust. See the USDA website at www.sbrusa.net for up-to-date information on sentinel plot results from Missouri and the rest of United States.

Articles for the Greenley Field Day were due July 11 so it will be interesting to see how the soybean rust picture has changed between July 11 and the field day on August 3. As of July 10, soybean rust had been moving slowly in the southern United States. The USDA Public Soybean Rust Website reported that soybean rust has been confirmed in 25 counties in five states. Most of these finds have been on kudzu and many occurred early in 2006. Over the first ten days in July there were several new finds on kudzu as well as three reports from soybean samples collected from sentinel plots (one each in Florida, Georgia and Alabama).

In addition to the sentinel plots, trials to evaluate the efficacy of various foliar fungicides against soybean rust at various rates and timings were established at Hundley-Whaley, Greenley and Bradford during the 2005 season and are being continued for the 2006 season. All three locations were planted with the same variety. For 2005 original protocols recommended a first application when soybean rust developed in the areas or when the threat of rust developing occurred. As the season progressed it became evident that soybean rust was not a serious threat in Missouri for the 2005 season. Treatments were applied when soybean plants were in the R3 stage of growth and only one application was made for the season. Fungicides were applied with a backpack CO₂ sprayer.

Septoria brown spot was fairly common and widespread at all three locations but other foliage diseases including soybean rust did not develop. Yields were taken at all locations. There were no significant differences in yield between treatments at the locations.

Soybean rust fungicides will be evaluated again during the 2006 season.