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The Relationship Between Epidemics of Septoria Leaf Blotch and Yield Losses in Spring Wheat. Zahir Eyal, Division of Mycology and Plant Pathology, Department of Botany, Tel-Aviv University, Israel; Oded Ziv, Division of Mycology and Plant Pathology, Department of Botany, Tel-Aviv University, Israel. Phytopathology 64:1385-1389. Accepted for publication 3 May 1974. DOI: 10.1094/Phyto-64-1385.

Methods for the assessment of Septoria leaf blotch progress curves in several spring wheat varieties grown at two locations in Israel were evaluated. Different amounts of disease resulted from changes in timing and number of applications of the fungicide Maneb. Disease progress curves were not satisfactorily defined when polynomic functions or logarithmic transformations were used in regression lines. Disease kinetics data were thus presented in an untransformed linear regression. The progress of Septoria leaf blotch in the dwarf variety Bet-Dagan 213, was significantly faster, and disease severity greater than that of the semi-dwarf Lakhish 221, grown under the same conditions. Disease severities of different Septoria progress curves were correlated to losses in yield and 1,000-kernal wt. Best estimates of losses were found with the linear expression of disease severities taken when the developing caryopsis had reached three-fourths its final size for four varieties at two locations. Wheat varieties showed differential vulnerability response to Septoria leaf blotch under similar epidemics caused by Septoria tritici.