Early season tan spot can be readily found across the Red River Valley. Especially in wheat on wheat situations the disease can readily be found. One of the characteristic symptoms of these infections at the 2 to 3 leaf stage is a yellowing discoloring of whole leaves. This is a more extreme expression of the same the yellow halo that surrounds the tan spot lesions in more mature plants. Be careful not to mistake this yellowing for a nitrogen deficiency.
There are a number of fungicides registered for control of early season leaf spot diseases in wheat. The table below lists the products that are available and the recommended use rates.
Research at both NDSU and the University of Minnesota has shown that once early season tan spot 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 susceptible cultivar are planted into wheat stubble. Even fields that were in wheat two years ago may have enough remaining wheat residue at the surface to see low levels of tan spot infection.
Most of the 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 (Puma, Discover, Axial, Silverado) and Bronate Advanced can result in some bromoxynil injury on the both wheat and wild oats. This injury generally didn't affect grain yield of the wheat or the control of the wild oat, except in the combinations that included Silverado in which case wild oat control was diminished.