There’s little evidence of the disease going into spring
Mother Nature can be your friend or foe. For a lot of farmers, she was the latter this past winter. One benefit of the brutally cold weather, though, is that researchers found little evidence of soybean rust overwintering on kudzu plants in the far South.
“We weren’t able to detect the disease on kudzu in Alabama and neither did my counterparts in states along the Gulf Coast,” says Ed Sikora, Auburn University Extension plant pathologist.
That is significant news because it means fewer spores are likely to be available to cause a disease outbreak in soybeans this spring.
In the Midwest, Daren Mueller, Iowa State University plant pathologist, does not anticipate soybean rust to present much of a threat, based on the “really solid cold spells” much of the South experienced.
“Everything would have to go wrong for it to be a problem [in the Midwest] this year,” he says.
That’s not to say soybean rust will not be a problem for some farmers. It simply means farmers are unlikely to see the severity and reach of the disease they saw in 2013 in the South and lower Midwest.
Hard hit. “It was a big problem here,” Sikora recalls. “We saw yield losses in some cases of more than 50%, which is more than we’ve observed in any of the previous eight years since we started tracking the disease.”
A tropical storm could have compounded the problem, he adds.
“If we’d had one come through here and move northward early in the growing season, things could’ve been a lot worse. Instead of rust being an Alabama problem it would’ve been a U.S. problem,” he explains.
Soybean rust was detected in 408 counties in 13 U.S. states in 2013, according to the Integrated Pest Management Pest Information Platform for Extension and Education. Total counties and parishes reporting rust problems included: 107 counties in Georgia, 82 counties in Mississippi,
67 counties in Alabama, 59 parishes in Louisiana, 22 counties in Florida, 20 counties in Arkansas, 13 counties in South Carolina, 10 counties in North Carolina, nine counties in Tennessee, eight counties in Virginia, four counties in Illinois, three counties in Kentucky and two counties in Texas.
Mueller says the work done by southern researchers and farmers to scout for soybean rust and raise the alarm when the disease is found has been a benefit for Midwestern farmers.
“We’ve had the luxury of not having to worry about it as much, which allows us to focus on the issues we face more often, such as sudden death syndrome and frogeye leaf spot,” he notes.
While the current threat of rust is low, it really depends on how the weather progresses. The lack of inoculum causes Sikora to think that when the disease does show up it will occur later in the growing season. However, he says wet weather conditions early in the growing season could allow the disease to build up quickly, and an active hurricane season could change things in a hurry.
On the other hand, if rust shows up after the soybean crop reaches pod fill, about R6, it is unlikely to be of much economic consequence, he adds.
David Wright, University of Florida Extension agronomist, says farmers’ fungicide use has notably curtailed soybean yield losses to rust in the state.
“Ninety-five percent of our growers use a fungicide application, and the average damage is less than 5% even though in most of our fields you could find some soybean rust,” he says.
For additional information on soybean rust, including current disease activity, visit www.FarmJournal.com/soybean_rust
