South Dakota Wheat Disease Risk Grows

By Scout Nelson

South Dakota wheat growers are being encouraged to begin early season scouting after the first positive Wheat Streak Mosaic Virus (WSMV) sample of the 2026 growing season was confirmed in winter wheat. The infected sample showed common symptoms including chlorosis and streaking, which are often linked to viral disease activity in wheat fields.

Madalyn Shires, Assistant Professor and SDSU Extension Plant Pathology Specialist, along with Connie Tande and Connie Strunk, highlighted that South Dakota experienced a major WSMV outbreak during 2025 in both winter and spring wheat fields. Experts warn that growers should carefully monitor wheat crops this season because early infections can greatly reduce crop yields when left unmanaged.

WSMV spreads through the wheat curl mite. Since there are no treatments available to cure infected plants, management focuses on limiting mite populations and reducing virus spread. Winter wheat, spring wheat, volunteer wheat, and wild grasses growing near fields can all support mites and the virus. These plants create what experts call a “green bridge,” allowing the disease to survive between growing seasons.

Farmers are encouraged to control volunteer wheat and border grasses using tillage or herbicides. Managing these areas can help reduce both mite activity and virus transmission during the season.

During 2025, WSMV was also detected in several late-season grasses, volunteer corn, and sorghum plants across South Dakota. These alternate hosts may continue supporting disease activity if not controlled properly. Warm late-season temperatures likely allowed mites to remain active longer than normal, increasing disease spread risks into 2026.

Two additional viruses connected to the WSMV complex, including High Plains Wheat Mosaic Virus and Triticum Mosaic Virus, were also confirmed in South Dakota during 2025. While their presence remained low, nearby states such as Kansas and Colorado continue reporting increased TriMV activity.

Extension specialists encourage continued scouting and monitoring across South Dakota wheat fields to help identify viral diseases early and reduce potential crop losses during the growing season.

Photo Credit: gettyimages-milos-cirkovic