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Missouri did participate in the Soybean Rust Sentinel Plot Program during the 2006 season. Twentyfour sentinel plots were distributed throughout the soybean production areas of the state. Samples of 100 terminal leaflets were submitted on a regular basis throughout the growing season to the lab at the University of Missouri. The leaflets were microscopically examined for the presence of soybean rust pustules. Until quite late in the season all of the samples submitted from the 24 sentinel plots were negative for soybean rust. By early October many of the original sentinel plots were either mature or the fields had been harvested. Sentinel plot scouts tried to locate adjacent fields that still had green leaves on plants to continue submitting samples from their counties.

In early October, soybean rust was confirmed in several counties in western Kentucky. Sentinel plot scouts were asked to make one last survey of their areas to sample any fields which still had either green plants or green leaves on scattered plants in fields. As a result of this end of the season survey soybean rust was found in five Missouri counties, Pemiscot, New Madrid, Scott, Stoddard and Mississippi counties. The hypothesis is that the front, which moved up from the southeastern US over September 21-23, may have deposited soybean rust spores in the southeastern area of Missouri as well as western Kentucky and Tennessee and other states along the Ohio River Valley.

For Missouri these soybean rust detections were so late in the season that soybean rust had no impact on yield. Most of the samples submitted that were positive had only one or two infected leaflets in the 100 leaflet sample and the number of pustules per leaflet was also quite low.

Across the United States for the 2006 season, soybean rust was confirmed on soybeans in 230 different counties in 15 states and (see USDA Public PIPE Website at www.sbrusa.net; figure below) for exact locations by state. When reports of soybean rust on kudzu are combined with the reports from soybean, soybean rust was confirmed in a total of 262 counties in 15 states during the 2006 season. Rust levels may have been severe enough to have impacted yield in some of the southern states. And research results from fungicide trials, yield loss trials, spore trap studies should be available in the near future from some southern states. For most states in the Midwest, the rust infections came in late enough in the season that yield was not affected and research trials will not have meaningful results related directly to soybean rust.

Laura Sweets
573-884-7307