MANHATTAN, KANSAS, U.S. — Kansas State University wheat disease specialist Erick DeWolf said a shift in summer rain patterns may have created a heightened concern for leaf rust disease, particularly in western parts of Kansas.
He said leaf rust — marked by small brown or brick-red lesions on leaves about the size of a pin head — is the second-most damaging wheat disease in Kansas, behind stripe rust.
“We often see leaf rust get established in the fall in our winter wheat crop,” DeWolf said. “When wheat is established on the early side, say for grazing purposes, it’s not uncommon to see leaf rust get established.”
The state’s producers are reporting symptoms of leaf rust in western Kansas, a change from past years when growers in the central part of the state were on alert.
“But this year with the rainfall pattern being switched around a little bit, parts of western Kansas did receive more rain,” DeWolf said, noting the disease often will cling to existence on volunteer wheat.
DeWolf said that two-thirds of the time, leaf rust in the fall is of only minor concern, because low winter temperatures kill leaf rust naturally. But this may not be one of those years.
He said some growers and consultants in western Kansas, “were expressing concern that the forage quality and grazing potential of wheat was being affected by the leaf rust. It was getting severe enough that it was yellowing up these wheat stands pretty severely and causing some concerns about how reliable a source of grazing and forage this would be as people looked at pasturing cattle on this wheat.”
He added that growers should plan to monitor wheat fields a little more closely this fall and winter, particularly in areas where there is a history of leaf rust. As February or March rolls around, they should check to see if the disease survived the winter.
“There are some fungicides that growers can use if they think that leaf rust is hurting them,” DeWolf said. “All fungicides are not equal, though, in the way they are labeled, and there are some restrictions on many fungicides with respect to when you can begin to chop that wheat for hay, using it for forage or for grazing purposes. There are some subtle differences in the way those labels are worded.”
For example, some fungicides require a seven-day interval between application and cutting for hay, while others require 30 days.
“I think it’s always advisable for people to be aware of what the label restrictions are as they are looking at these fungicide products, and asking the right questions to make sure they’re making an informed decision and not boxing themselves into a corner,” DeWolf said.