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This NebGuide describes the development of tan spot disease in wheat and gives recommendations for controlling it by means of crop rotation, fungicides and good crop residue management.
Tan spot, caused by the fungus Pyrenophora tritici-repentis, is a major leafspot disease of winter wheat in the Great Plains of North America. It has become an increasing problem in wheat cropping systems using conservation tillage. Although tan spot can be a serious threat by itself, it more often occurs as a part of a foliar disease complex involving tan spot, leaf rust and Septoria leaf blotch. Usually tan spot symptoms appear in early April, but the greatest yield losses result during grain fill when severe spotting reduces the photosynthetic area of the upper leaves. The most severe damage occurs from boot to dough stage, and is greatest on late tillers.
Wheat, bromegrass and wheatgrass are the primary hosts for P. tritici-repentis. Barley and rye are less frequently attacked and oats appear immune.