While it failed to reach Missouri in 2005, soybean rust did emerge in the southeastern United States during the growing season, allowing researchers there to learn more about combating the disease in the future.

"Soybean rust was not as explosive as we feared it might be this year," Layla Sconyers, research associate at the University of Georgia, told participants at the University of Missouri Crop Management Conference, Dec. 14-15 in Columbia. "In terms of a wind-blown disease, it was crawlin' on its belly."

The yield-reducing foliar disease first appeared in the continental United States in November 2004 in Louisiana. For several years prior, rust had posed a significant problem for South American soybean production, causing yield losses between 10 and 90 percent. When discovered in the United States, federal, state and university researchers initiated plans to scout, monitor and manage the disease if it emerged in 2005.

"We had our first find in Seminole County in April on volunteer soybeans," Sconyers said. "The disease progressed north, moving an average of 60 miles a week during the season."

As in other soybean-producing states, University of Georgia researchers established sentinel plots to detect the disease as early as possible in soybeans and on other host species, including kudzu and clover. Spore trapping also took place to monitor potential disease movement. As of Dec. 7, soybean rust had been reported in 35 counties in Georgia where producers planted about 200,000 acres to soybean in 2005.

University of Missouri researchers and MU Extension agronomists likewise scouted soybean fields throughout the season, but did not find the disease.

Because soybean rust did emerge in Georgia, Florida, Alabama and South Carolina, researchers there were able to conduct fungicide trials to determine what products, product combinations and application timings were most effective.

"It's only one year of data, but I think we learned that soybean rust can be managed," Sconyers said. "We had treated plots right next to untreated plots in our trials, and there were significant differences."

Although fungicides with the active ingredient chlorothalonil were much less effective at controlling soybean rust, the Georgia trials found that triazole, strobilurin and triazole-strobilurin mix products did provide benefits.

Foremost among Georgia's first-year findings was the importance of early application of fungicides when soybean rust appeared. "That first application is very critical," Sconyers said. "Waiting a little later was not good. That application may not necessarily be at the R1 growth stage (as in Georgia's research trials), but timely application when rust appears is a must."

Sconyers estimated that about 60 to 70 percent of Georgia soybean producers applied fungicides to combat soybean rust in 2005.

"Two applications were most common among growers, but the epidemic varied across the state, so some got away with one application," she said. "There was some unnecessary spraying, but we encouraged them to wait as late as they could because we didn't want our growers throwing away dollars."

Georgia will continue its monitoring and fungicide trial program in 2006, Sconyers said. Research also continues this winter to evaluate the disease's ability to over-winter.

"It's important that producers don't lose focus on the basics of managing fertility, insects and other diseases," she said. "We need to continue to be proactive with our scouting and monitoring efforts, and if we do that, rust can be managed."

More details about the University of Georgia's 2005 fungicide trial results can be found in the Dec. 7 issue of the UGA Soybean Newsletter, available online at http://www.griffin.peachnet.edu/caes/soybeans/snl120705.pdf.