Authors: Erick De Wolf, Romulo Lollato, Mary Knapp

Wheat stripe rust continues to emerge as a serious problem in many areas of Kansas. Key developments this week include the detection of stripe rust on the upper leaves of the wheat crop in many counties in central Kansas (Figure 1). This is important because these upper leaves are critical for production of the grain, as the flag leaf and flag leaf-1 can produce as much as 90% of the photosynthates used for grain fill. We also have received reports of low levels of the disease in the western regions of the state. The weather forecast suggests continued cool temperatures and above normal rainfall for the next few weeks (Figure 2). These conditions will favor continued development of stripe rust.

Wheat varieties that are known to be susceptible to stripe rust should be a top priority for scouting and protecting with fungicides. The evidence to date suggests that the stripe rust reaction of our wheat varieties this year is very similar to last year. The list of susceptible varieties includes Armour, Byrd, Denali, Everest, KanMark, RedHawk, Ruby Lee, TAM 111, TAM 112, and Winterhawk. These varieties represent some of the most widely planted varieties in the state. Varieties that are looking more resistant include Oakley CL, SY-Monument, T158, WB4458, and WB-Grainfield. These resistant varieties will often have some low levels of disease, but the rust develops more slowly and often remains less severe during the critical stages of grain development.

Figure 1. Current distribution of wheat stripe rust in Kansas based on observations from K-State Extension.
Figure 2. Long-range forecast for rainfall from the NOAA. Much of Kansas is projected to have above-normal rainfall, which would increase the risk of severe disease problems in wheat.

Erick De Wolf, Extension Plant Pathologist

Romulo Lollato, Wheat and Forages Specialist

Mary Knapp, Kansas Weather Data Library