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Asian soybean rust hits Kentucky

Asian soybean rust was detected on soybean for the first time ever in Kentucky on Friday, Oct. 6. Between then and now, it was found on soybeans in seven counties in the western part of the state.

The infected counties are Caldwell, Christian, Hopkins, Lyon, Marshall, Todd and Union. Last year, only Caldwell County had any rust, and that was on kudzu, discovered Nov. 11, 2005.

The U.S. count is now 110 infected counties in nine states. These new finds are much further north than any other U.S. rust locations in 2006.

Don Hershman, plant pathologist with the University of Kentucky, posted the Kentucky state commentary on www.sbrusa.net, the U.S. Department of Agriculture's rust monitoring site.

"Soybean rust was detected on soybean for the first time ever in Kentucky on Friday, Oct. 6, 2006. The find was in the corner of an otherwise mature sentinel plot located at the UK Research and Education Center in Princeton. Incidence was about 40% to 50%, and severity around 10%," Hershman wrote Wednesday. "Then, between Sunday Oct. 8 and Tuesday Oct. 10, soybean rust was detected at various levels in six additional counties -- Christian, Hopkins, Lyon, Marshall, Todd and Union Counties. All of the finds, thus far, are in the lakes region of west Kentucky. Finds were in "mobile plots," except for the Caldwell and Union County finds, which were in sentinel plots.

"Incidence in additional counties was generally low (0.1% to 10%). With the exception of the Hopkins County find, which had extremely low severity (less than 0.1%), severity in the other finds was around five to 15%," Hershman added.

Hershman believes spores blew in two weeks ago. At this late stage in the growing season, he expects the spores to have no effect on this year's crop.

"For all finds, the stage of pustules was mostly uniform," he said Wednesday. "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. 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.

"This find will have absolutely NO impact on the 2006 soybean crop in Kentucky or anywhere else for that matter. In fact, soybean rust will 'go away' from Kentucky as soon as there is hard frost. It simply cannot survive this far north."

Despite the relative lack of danger from the rust spores found this week in Kentucky, Hershman said the rust discovery is important in demonstrating the efficacy of the nation's soybean rust monitoring and predictive systems.

"These finds are of great importance to the soybean rust predictive models. Thus, we are making great effort to know the extent of infection before the frost hits (maybe tonight) or until there are no soybean leaves in which the rust can survive (the disease has NOT been seen in kudzu here)," Hershman said. "I am hoping to find a location that has decent infection that would provide for an educational opportunity or two.

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

Asian soybean rust was detected on soybean for the first time ever in Kentucky on Friday, Oct. 6. Between then and now, it was found on soybeans in seven counties in the western part of the state.

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