October 11, 2006 | By: Laura Skillman

Asian Soybean Rust has been found on soybeans in western Kentucky. This marks the first time the disease has been found on soybeans in the state, but its late arrival will mean no damage to the crop.

Researchers with the University of Kentucky College of Agriculture confirmed the finds on soybeans in Caldwell, Christian, Hopkins, Lyon, Marshall, Todd, and Union counties.

“This find will have absolutely no impact on the 2006 soybean crop in Kentucky or anywhere else for that matter,” said Don Hershman, UK Extension plant pathologist. “In fact, soybean rust will "go away" from Kentucky as soon as there is hard frost. It simply cannot survive this far north.”

These finds are of great importance to the soybean rust predictive models, he said. So researchers are making a great effort to know the extent of infection before the frost hits or until there are no soybean leaves in which the rust can survive. The disease has not been seen in kudzu in Kentucky this year.

The initial find, on Oct. 6, was in the corner of an otherwise mature sentinel plot located at the UK Research and Education Center in Princeton, said Don Hershman, UK Extension plant pathologist. Incidence was about 40 to 50 percent and severity around 10 percent. Then, between Oct. 8 and Oct. 10, rust was detected at various levels in the six additional counties. All of the finds, thus far, are in the lakes region of western Kentucky.

The finds were in "mobile plots" except for the Caldwell County and Union County finds, which were in sentinel plots. Incidence and severity of the disease was generally low.
“For all finds, the stage of pustules was mostly uniform. This suggests to me that a large number of spores blew in sometime over the past two weeks and cut a pretty large swath in west Kentucky,” Hershman said. “We are in the process of looking to the west and east to see if an even larger area of spore deposition and infection may have occurred.” 

Rust has also been found in soybeans in Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, North Carolina and Texas. In Kentucky, 20 sites in 17 counties are being monitored for the disease on either kudzu or soybeans.

The fungal disease had been found in all major soybean growing areas of the world except the United States until its discovery in November 2004. Officials believe spores of the disease may have been carried into the area by hurricane winds. The disease poses potentially devastating losses in soybean yields, but it poses no risk to human health.

Since that discovery, crop and disease specialists across the soybean growing region have been working to understand how the disease develops and its impact on the crop. They have also been educating producers, field scouts, agricultural suppliers and others about this new threat.

“The bottom line is this: the soybean rust finds will not impact soybeans in Kentucky or the U.S. this year,” Hershman said. “But, they will help us to refine soybean rust predictive models, which will help greatly with soybean rust management in future crops.”

Up-to-date information on soybean rust in Kentucky and across the country can be found on the Internet at http://www.sbrusa.net or by calling 888-321-6771.


Don Hershman, 270-365-7541, ext. 215