Mississippi lost a tiny portion of its crop to soybean rust last year, but Tom Allen of Mississippi State says his team identified one field that had an estimated 25% yield loss based on the grower’s harvested yield (45 bushels/acre), compared with a neighbor’s field that was planted in about the same time frame (60 bushels/acre). The difference: The neighbor applied an R4 growth stage strobilurin fungicide.
Scott Monfort, University of Arkansas Extension plant pathologist, says 2009 was the first year soybean rust caused widespread damage in his state. Of 3.5 million acres planted, he estimates about 600,000 acres of soybeans were sprayed. Some Extension plots saw yield losses of 15%. If rust is seen in fields, he cautions growers not to panic and start spraying unnecessarily. They should follow Extension e-mails and updates to track the disease’s progress. “We’ll let them know the risk,” he says. Monfort also encourages producers to get out themselves and scout.
“Soybean rust has yet to cause yield loss in any Midwestern states,” says Daren Mueller, Extension plant pathologist with Iowa State. But with the widespread movement of the disease throughout the Southeast in 2009, he says his team will be keeping an eye on how well the pathogen overwinters. It needs a living tissue host to survive, and the good news is that some cold snaps have dipped fairly far south, he reports.