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Ecology and Epidemiology

Interactions Between Septoria nodorum Leaf Blotch and Leaf Rust on Soft Red Winter Wheat. V. J. Spadafora, Former Graduate Student, Department of Plant Pathology, Pennsylvania State University, University Park 16802, Present address: Chevron Chemical Company, Ortho Research Center, P.O. Box 4010, Richmond, CA 94804-0010; H. Cole, Jr., Professor, Department of Plant Pathology, Pennsylvania State University, University Park 16802. Phytopathology 77:1308-1310. Accepted for publication 10 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1308.

Interactions between Septoria nodorum leaf blotch and leaf rust were investigated under field conditions in Pennsylvania in 1985 and 1986. Various levels of leaf rust severity were established by altering the frequency and timing of triadimefon fungicide applications. Analyses of variance indicated significant effects of fungicide treatments on the severity of leaf rust but no effects on the severity of Septoria nodorum leaf blotch in both years. Regression analyses on treatment means, however, indicated significant inverse relationships between the severities of the two diseases. Control of leaf rust with specific fungicides may increase the potential for Septoria nodorum leaf blotch epidemics and should be considered in the evaluation of narrow-spectrum fungicides.