The week of April 8-14 has brought more reports of leaf rust in the region. Texas and Oklahoma continue to report moderate to severe leaf rust in their wheat crop with reports as far north as Stillwater, Oklahoma. In Kansas, leaf rust was spotted for the first time about a week ago when Zach Simon, Sedgwick County Research and Extension agent, reported the disease in Sedgwick County. Leaf rust has since been reported in additional counties in south central Kansas (Figure 1). These reports of leaf rust are important because the disease is most damaging when it becomes established in a field prior to the heading and flowering stages for growth.
Some popular varieties in central Kansas -- including 1863, T158, and WB 4458 -- are susceptible to leaf rust. Important varieties in western Kansas that could also be vulnerable include TAM 111, TAM 112, Denali, and Byrd. Growers with these varieties should be scouting for leaf rust regularly as their crop moves into the heading stages of growth.
Figure 1. Current distribution of leaf rust in Kansas.
Tan spot (Figure 2) and powdery mildew (Figure 3) are also getting a foothold in some fields in central Kansas. The fungus that causes tan spot survives in wheat residues left over from previous years. Tan spot is often most severe in fields with large amounts of wheat residues on the soil surface. The fungus reproduces on these residues and is spread by wind or splashing rain to the newly established wheat crop. Powdery mildew is showing up in the lower and middle canopy of some varieties. Powdery mildew can become a problem if cool humid weather continues to favor spread of the disease.
The presence of leaf rust, tan spot, and powdery mildew in wheat fields is cause for concern. Fields with tan spot and/or powdery mildew in the lower canopy, and with even traces of leaf rust or stripe rust becoming established on the upper leaves, would likely benefit from a fungicide application.
Figure 2. Wheat with symptoms of tan spot. Photo by Erick DeWolf, K-State Research and Extension.
Figure 3. Wheat with symptoms of powdery mildew. Photo by Erick DeWolf, K-State Research and Extension.
For more information on tan spot see:
Erick De Wolf, Extension Plant Pathology
Romulo Lollato, Wheat and Forages Specialist