Sentinel plots, established throughout the country last year as the first line of defense against soybean rust, will again be a part of the plan to monitor the disease this growing season.

Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center and the state's leading soybean rust expert, said that Ohio will maintain its 45 sentinel plots.

"The sentinel plots worked and they worked very well, and we got good participation from the counties. The Extension Educators did an outstanding job scouting the sentinel plots," said Dorrance, who also holds an Ohio State University Extension appointment. "Because of the sentinel plots placed throughout the south we will know a month ahead of time if we are going to be at risk from soybean rust during 2006."

According the U.S. Department of Agriculture, sentinel plots have been established in over 30 states and Canada, stretching as far south as Florida, as far north as Ontario, as far east as Delaware and as far west as Washington.

A total of 138 counties throughout the United States tested positive for soybean rust last year. The closest soybean rust got to Ohio was Kentucky, where one rust pustule was found on kudzu in November, long after the soybean crop had been harvested. This year, the extent of the disease's spread will hinge on how well wintry weather in the south will hold the disease back.

"The big questions are how low will the freeze line go in the south and how soon will the inoculum build up this spring," said Dorrance. "We've been having anything but a normal winter this year, so anything can happen."

So far this year the USDA has reported positive soybean rust finds on kudzu in Alabama, Georgia and Florida.

"Even if we get a lot of inoculum build-up this year, an unexpected epidemic in Ohio would be unlikely," said Dorrance. "At just a 3 percent infection level in soybean fields across the state, we would have to have 12 million spores hit every acre in the state all at the same time. With five million acres, that just doesn't compute, and we'd know that soybean rust was present long before it ever reached that level because it would be everywhere."

Nonetheless, researchers are keeping a close watch on the disease's potential path north. Soybean rust can enter Ohio through a variety of routes: south through Kentucky, from North Carolina over the Appalachian mountains, or up the Mississippi River and along the Ohio River through southern Indiana and western Kentucky.

"The network is in place. It's safe to say we've got all of that covered," said Dorrance.

For the latest information on soybean rust, log on to the USDA's Soybean Rust Information Site at http://www.sbrusa.net.

OARDC plant pathologist Dennis Mills will provide a soybean rust update at the Conservation Tillage and Technology Conference, being held Feb. 23-24 at Ohio Northern University in Ada, Ohio. For more information, log on to http://ctc.osu.edu.