Ohio to see soybean rust this season; timing may impact crop success

WOOSTER, Ohio – Ohio growers are likely to see soybean rust this year, says an Ohio State University Extension and research plant pathologist.
But the question remains whether the disease will show up early enough to have any impact on the crop.
“At some point we will probably encounter low levels of the disease, but at what point during the growing season is an uncertainty,” said Anne Dorrance, the state’s leading soybean rust expert with the Ohio Agricultural Research and Development Center.
“When it arrives will determine what fungicide application strategy to use, if any at all.”
Weather’s work. Favorable weather conditions are driving speculation that soybean rust will make its first appearance in Ohio this year.
“Last year, though arriving too late to have any impact, soybean rust showed up on kudzu in Kentucky in November, and the disease survived over winter in Florida and in Alabama,” said Dorrance.
According to the USDA’s Soybean Rust Information Web site, new infections of soybean rust were confirmed in the Florida panhandle in mid-May.
To date for the 2006 season, rust survived the winter on kudzu patches in five counties in Alabama, 11 in Florida, four in Georgia and one in Texas.
This time last year, only Florida and one spot in Georgia confirmed findings of soybean rust. The disease didn’t begin actively spreading throughout the south until August.
Sentinel plots. OSU Extension educators will be relying on the 36 locations in Ohio where sentinel plots will be the first line of defense in identifying the presence of the disease in the state.
Ohio, once again, has joined 30 other states and Canada in this effort. All of Ohio’s plots have been planted.
“The sentinel plots worked last year 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.
“Because of the sentinel plots placed throughout the southern states we will know a month ahead of time if we are going to be at risk from soybean rust during 2006.”
Discounted. If soybean rust were to hit Ohio, even at the height of the growing season, an epidemic is being discounted.
“Even if we get a lot of inoculum buildup 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 5 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.”
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.