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Losses in Wheat Caused by Pyrenophora trichostoma and Leptosphaeria avenaria f. sp. triticea. R. M. Hosford, Jr., Associate Professor, Department of Plant Pathology, and R. H. Busch, Department of Agronomy, North Dakota State University, Fargo 58102. Phytopathology 64:184-187.

In North Dakota in 1970 and 1971, a complex of similar leaf spots caused by Pyrenophora trichostoma and Leptosphaeria avenaria f. sp. triticea caused moist-weather losses averaging 12.9% in grain yield and 1.0% in test weight in spring wheats and durums.  In dry weather these fungi caused little spotting and no losses.  Maneb plus zinc ion fungicide controlled these losses.  Inoculum usually traveled at least several meters in amounts sufficient to cause severe leaf spotting and yield loss.  Abundant conidia of P. trichostoma were found in South Dakota in June and in North Dakota in July of 1972 on standing winter wheat.  These conidia could serve as a source of secondary inoculum for infecting spring and durum wheats.  Resistance to leaf spotting and influence of moisture on foliage in the glasshouse was related to resistance to yield loss and leaf spotting in the field.

Additional key words: Septoria avenae f. sp. triticea, S. nodorum, Helminthosporium tritici-repentis, H. tritici-vulgaris, Triticum aestivum, T. turgidum, epidemiology.