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Disease Detection and Losses

Effects of Leaf and Glume Blotch Caused by Leptosphaeria nodorum on Yield and Yield Components of Soft Red Winter Wheat in Pennsylvania. V. J. Spadafora, Former graduate research assistant, Department of Plant Pathology, Pennsylvania State University, Present address: Chevron Chemical Company, Ortho Research Center, P.O. Box 4010, Richmond, CA 94804-0010; H. Cole, Jr.(2), and J. A. Frank(3). (2)Professor, Department of Plant Pathology, Pennsylvania State University; (3)Research plant pathologist, USDA-ARS, University Park 16802. Phytopathology 77:1326-1329. Accepted for publication 2 March 1987. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-1326.

Epidemics of Septoria nodorum blotch were established in field plots of the soft red winter wheat cultivars Hart and Tyler. A range of disease severity was generated by manipulating irrigation, inoculum pressure, and fungicide treatment in two seasons. Yields were most consistently correlated with the disease severity of the leaf below the flag leaf at the Feekes growth stage 11.1. Estimated slopes of disease-yield relationships for the two cultivars were not equal and indicate differences in tolerance to disease. Yield was correlated with kernel weight in both cultivars and with the number of kernels per spike in the cultivar Tyler. For certain cultivars, the optimum time for fungicide application may be earlier in the epidemic or at an earlier growth stage than previously thought.