The Effect of Fungicide Schedules and Inoculum Levels on Early Blight Severity and Yield of Potato. B. J. Christ, Assistant Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. S. A. Maczuga, Graduate Student, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 73:695-698. Accepted for publication 28 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0695.

Several fungicide spray schedules were evaluated for their effect on controlling potato early blight under Pennsylvania growing conditions. Disease severity and lesion number were lowest when fungicide sprays were initiated before flowering of the potato plant. Lowest disease incidence and highest yield of U.S. no. 1 tubers occurred in plots with low inoculum density and in plots where fungicide sprays were initiated before flowering. Whereas fungicide spray schedules had a significant effect on yield in 1985, there was no effect on yield in 1986. The relationship between lesion number and yield in 1985 was not highly correlated. Inoculum level was directly proportional to the early blight severity that occurred during the 1986 growing season.