The finding of soybean rust on leaf tissue in an Iowa grain bin maybe reason for continued vigilance among Wisconsin producers, but it's not necessarily doom and gloom. That's according to Brian Kuhn, Plant Industry Bureau Director at the Wisconsin Department of Agriculture, who says soybean rust damages yields and can potentially impact international trade, but poses no health threat to humans or animals.
"Although we've never found soybean rust in Wisconsin, this is a reminder that we could find soybean rust in Wisconsin in the future, and we'll continue the surveillance we've done for the past several growing seasons," Kuhn says. "Growers need to remain vigilant for Asian soybean rust, but they shouldn't treat for it unless it's actually established in the area."
On Tuesday, the Iowa Department of Agriculture and Land Stewardship reported that soybean rust had been found on leaf residue in a grain bin containing beans from the 2006 harvest. Asian soybean rust was first detected in the United States in 2004. Scientists believe that the active hurricane season the southeast U.S. experienced that summer swept reproductive spores northward.
The fungus attacks the leaves of the plant and stops photosynthesis, which is the process of the plant producing food for itself.
Meanwhile, Kuhn reminds producers that the reproductive spores in rust are very short-lived and need a living green host plant to survive.
"The fungus cannot overwinter in northern climates like Wisconsin or Iowa," he points out. "We may find it at some point in Wisconsin, but it would have to blow in from other areas. It won't overwinter here from year to year."
The good news is there are a number of fungicides temporarily registered to treat soybean rust. Pre-emergent pesticides, which are applied before plants emerge from the soil, are not effective against soybean rust. But Kuhn says producers don't need to go to the expense of preventive treatments.
"These should be used only when there's a confirmed threat. All the treatments must be timed for particular growth stages."
If producers suspect a problem, they should call their county extension agent or the state agriculture department at 866-440-7523.