Source: Marcia McMullen, Extension Plant Pathologist, North Dakota State University
Winter wheat fields in southeast and south central counties of North Dakota are in the head emergence to early flowering stage in many fields (June 1). The Fusarium head blight (fhb = scab) model indicates very low risk of scab infection in these locations at this time. Recent weather in the south and eastern portions of North Dakota was not favorable for infection as relative humidities were very low.
In contrast, relative humidities were very high over the past week in the northwest and north central regions, and the model does indicate high risk of infection for any winter wheat flowering in the these areas of North Dakota. However, reports from area extension specialists at Williston and Minot indicate that most, if not all, winter wheat fields in those areas are not yet headed. Growers with winter wheat in the boot stage to early heading stages should keep watching the scab forecast and weather conditions for potential risk of scab.
No Rust Observed Yet in North Dakota
No stripe rust or leaf rust of wheat was observed in Ransom or Sargent county scouting of winter wheat and spring wheat on June 1. We will keep looking in our scouting program, as stripe rust is being observed commonly on winter wheat in Nebraska now, as well as low levels of leaf rust.
Tan Spot in Wheat
Tan spot fungal leaf infections are the most common disease observed in winter and spring wheats. Levels of infection vary considerably, depending on amount of old wheat residue present and recent weather conditions. Where residue is abundant and dews have occurred, tan spot is severe. The NDSU Small Grain Disease forecasting model indicates risk of tan spot in those areas of the state where more rainfall has occurred in the past week.