Fortunately for Minnesota's soybean producers, soybean rust did not rear its ugly head in the state during 2005. Looking back, what happened with soybean rust in the U.S. in 2005 and what should we expect for 2006?

Soybean rust was confirmed in nine states including Alabama, Florida, Georgia, Mississippi, South Carolina, North Carolina, Louisiana, Texas, and Kentucky in 2005. The earliest findings were on kudzu, an alternative host of soybean rust, but the disease was discovered in many soybean fields as well as more kudzu patches later in the season. The disease spread more slowly across the southeastern U.S. than originally anticipated and was sporadic in occurrence.

Sentinel plots, spore traps, and rainfall collectors were utilized to help track disease development and spore movement throughout the United States in 2005. In many areas, soybean rust was first detected in sentinel plots. Although no soybean rust was confirmed in Minnesota or surrounding states in 2005, it appears that soybean rust spores made their way to the region and state.

Asian soybean rust DNA was detected in rainwater collected during July 19-26th in National Atmospheric Deposition Program (NADP) rainfall collectors located at Lamberton and Cottonwood, SD. This does not mean we actually had soybean rust in MN or SD in 2005. Soybean rust was not confirmed in either state.

The mere presence of soybean rust spores does not mean disease will develop. First of all, we do not know if the spores that made their way to MN and SD were even viable. We also don’t know how many spores were deposited in the rain collector. Furthermore, environmental conditions must also be favorable for soybean rust or any other plant disease to develop.

What this finding does confirm is that we should continue to be vigilant in our scouting and monitoring of soybean rust in 2006. Sentinel plots are planned for Minnesota once again in 2006, spore traps will be used again, and a network of First Detectors has been established. First Detectors have been trained in identifying soybean rust and other soybean diseases and can be valuable for ruling out other diseases when looking for soybean rust (contact your local County Extension Office for a list of First Detectors in your area). Experience from southeastern U.S. confirmed that soybean rust is difficult to detect and properly identify in its early stages.

The USDA website http://www.sbrusa.net will continue to be a valuable tool in tracking spread of the disease in 2006. Early reports from Florida in 2006 suggest that soybean rust may be overwintering in a larger area than last year. The University of Minnesota's Soybean Management website http://www.soybeans.umn.edu/home.htm is another valuable resource on soybean rust and other soybean information.

Fortunately growers in Minnesota did not have to deal with soybean rust in 2005. Hopefully we will not have to deal with it in 2006 either. We have much to learn about soybean rust in the U.S., and soybean rust continues to be a potential threat to Minnesota. Although the odds of significant disease development in any particular year may be low, the odds are greater than zero. Tracking development and movement of soybean rust throughout the U.S., scouting for the disease at key times, and having a plan for fungicide use in case there is an outbreak, will help us manage this disease if it becomes an issue in the upcoming growing season.

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