Volunteer wheat can create a "green bridge," providing a route for mites to move to and infest emerging wheat. These mites can then transmit wheat streak mosaic virus, High Plains virus, and Triticum mosaic virus, or all of them to create a complex of infections.
Some wheat growers who treated for fusarium head blight at flowering (the optimum timing) with a triazole fungicide (the most effective fungicide class for this disease) are wondering why they aren't seeing the control they expected this year.
Excessively wet field conditions are contributing to the development of Fusarium head blight (scab) in some wheat fields. The disease is characterized by premature whitening or bleaching of wheat heads. As scabby grain contains a mycotoxin, it requires special harvest and separation procedures, as outlined here.