Wheat streak mosaic severe in some wheat
Some winter wheat plots in North Dakota have been so severely infected with wheat streak mosaic virus, that these plots were destroyed to prevent further movement of the wheat curl mite and virus to neighboring fields. Questions have arisen as to the source of the wheat curl mite for these plots and also for some commercial winter and spring wheat fields with infection.
Grass hosts most susceptible to the mite and the virus include wheat, corn, sorghum, cheat grass, field sandbur and jointed goatgrass. Grass hosts that are susceptible to the virus, but poor hosts for mite increase include oat, barley, rye, barnyard grass and green foxtail. Neither the virus or the mite survive in or infect broad leaf crops.
Although wheat crops or volunteers are the primary source of infection and mites, grasy weeds in fields or along field edges may serve as sources for the virus and mite. The NDSU Extension Publication PP-646 www.ag.ndsu.edu/pubs/plantsci/smgrains/pp646.pdf and the University of Nebraska Publication http://elkhorn.unl.edu/epublic/live/ec1871/build/ec1871.pdf have more information on mite and virus hosts and mite movement.
Later this growing season, when growers will be considering planting winter wheat again, extreme care must be made on what ground they plant into, and how volunteers or grassy weeds will need to be destroyed prior to planting. This disease also has implications for cover crop choices, as we don't want a lot of virus present in cover crops.