Soybean Rust Outlook

March 20, 2014 01:24 AM
Soybean Rust Outlook

Researchers see little evidence of the disease going into spring.

Mother Nature can be your friend or foe, and a lot of farmers believe she has been largely the latter most of this winter. One plus from the tough cold weather conditions she has dished out, though, is that researchers have found little evidence of soybean rust overwintering on kudzu plants in the far southern regions of the U.S.

"We haven’t been able to detect the disease on kudzu here in Alabama or from my counterparts in states Coast along the Gulf" says Ed Sikora, Extension plant pathologist at Auburn University.

That is significant news as it means fewer spores are likely to be available to cause a disease outbreak in soybeans planted later this spring, Sikora notes.

Daren Mueller, Iowa State University plant pathologist, adds that he does not anticipate soybean rust to present much of a threat to Midwest crops in 2014, based on the "really solid cold spells" much of the South experienced this winter.

"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 that they saw last year through much of the South and into the lower Midwest.

"It was a big problem here," Sikora recalls. "We saw yield losses in some cases of more than 50%, 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.

As it was, 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 (IPM-PIPE). 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 huge benefit for growers in the Midwest.

"We’ve had the luxury of not having to worry about it as much, which has allowed us to focus more 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, how the weather conditions progress this spring will influence the level of rust farmers ultimately see. The lack of inoculum causes Sikora to think that when the disease does show up it will occur later in the 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.

If rust shows up any time after the soybean crop reaches pod fill, about R6, it is unlikely to be of much economic consequence, he says.

David Wright, University of Florida Extension agronomist, says farmers’ fungicide use has significantly 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 in it," he says.

Wright and Sikora teamed up earlier this year, along with other land-grant university researchers from around the country, to develop two rust videos for farmers’ reference.

The first video provides an overview of soybean rust, its impact and spread in the U.S., and how responding to this disease has changed the way researchers, Extension educators and farmers now approach soybean diseases in general.

The second video deals with efforts undertaken across the country to model, predict and forecast soybean rust through the use of sentinel plots.

Additional information on soybean rust, including the current disease activity, is available at
the USDA Integrated Pest Managment website.


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