Research at both NDSU and the University of Minnesota has shown that once early season tan spot in wheat is left uncontrolled, yield reductions of 4 to 5 bushels will result if conditions continue to favor the development. The greatest economic response from early season fungicide use occurs when a susceptible cultivar is planted into wheat stubble. Even fields that were in wheat two years ago may have enough remaining wheat residue at the surface to allow tan spot to start.
Little data is available on the economic benefits of controlling leaf blotch of oats or barley early in the season. However, if the cooler than normal weather conditions return after this week's forecasted temperatures, the disease will likely continue to migrate upwards in the canopy, similar to how the disease progresses in spring wheat.
There are a number of fungicides registered for control of early season leaf spotting diseases in small grains (see here:
https://z.umn.edu/4d62 ). The recommendation is to use half a labeled rate of the registered product. Most of the labeled fungicides can successfully be tank mixed with the commonplace herbicides. Always check the label of both the herbicides and fungicides for tank mix restrictions.
Research at the Northwest Research and Outreach Center has shown that the combination of any of the EC formulations of fungicides in combination with the common wild oat herbicides and Bronate Advanced can result in some bromoxynil injury on both wheat and wild oats. This injury generally didn’t affect grain yield of the wheat or the control of the wild oat.