June 13, 2007 | By: Laura Skillman

Three years after its first appearance in the United States, soybean rust has not yet been an issue for Kentucky farmers. But, that's no reason to let their guard down, says a University of Kentucky plant pathologist. In fact, not being vigilant could be devastating.

“Complacency is the worst thing that could happen,” said Don Hershman, UK plant pathologist. “The disease is doing exactly what we’d expect it to do, because it takes several years for it to really get established in the south. You’ve got to realize there’s kudzu everywhere, and that’s where it is going to overwinter. What’s happening is every year more and more places are getting infested, and it’s becoming endemic in those areas.”

So, as farmers are busy planting this year’s soybean crop, scientists around the country are again watching to see if the disease will spread from overwintering areas in the South into the Midwest. In Kentucky, Hershman is overseeing the monitoring of 15 soybean plots and seven kudzu patches for the disease as part of a national sentinel plot network. The network organized when the disease was discovered to be in the United States in the fall of 2004.

This year rust has appeared in a kudzu patch in Louisiana nearly two months earlier than in 2006. It is now in two counties in Louisiana and one in Texas, so it is beginning to increase. Knowing what’s happening in the middle of the country is important because that’s where Kentucky’s weather patterns frequently come through, Hershman said.

“The main thing is it needs to build up in significant levels in some area, and that hasn’t happened yet. The weather had kept it in check and the amount that overwinters sets the bar for the year,” he said. “It really depends on what happens this next month in Louisiana, Texas, Mississippi and Arkansas. 

“We know once it is established somewhere, there are a lot of spores waiting to blow into an area through a storm front,” he said. “That’s what happened last September when a single storm blew through Louisiana and covered about 1,500 miles with spores in a weekend. It distributed them from Lexington to Fayetteville, Ark.”

Last year, the disease arrived late in the growing season so it caused no damage. Hershman’s point however, is that the disease can move very quickly when there are spores to move.

“When you see the disease, it is pretty impressive. There’s nothing like it,” he said. “It can cause total devastation. It’s nothing to play with. We’ve learned a lot in the past couple of years. We have a pretty good system of monitoring the weather systems and disease activity. When the time comes to recommend spraying, the recommendation will be made when the farmer still has time, and they don’t need to do it within 24 hours or it’s all over.”

To keep farmers up-to-date on rust, Hershman regularly updates the Kentucky rust hotline 800-321-6771, sponsored by the Kentucky Soybean Promotion Board; the U.S. Department of Agriculture’s rust Web site; and the UK soybean rust Web site.


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