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Field and Computer Simulation Evaluation of Spray-Scheduling Methods for Control of Early and Late Blight of Potato. D. Shtienberg, Department of Plant Pathology, 334 Plant Science Building, Cornell University, Ithaca, NY 14853, Present address: Hebrew University of Jerusalem, Faculty of Agriculture, Department of Plant Pathology and Microbiology, P.O. Box 12, Rehovot 76-100, Israel; W. E. Fry, Department of Plant Pathology, 334 Plant Science Building, Cornell University, Ithaca, NY 14853. Phytopathology 80:772-777. Accepted for publication 15 January 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-772.

Field experiments corroborated a reduced-sprays strategy which had previously been devised through analysis of experiments using complex computer simulators. The reduced-sprays strategy was designed to efficiently suppress both early and late blight in potato foliage. Tuber blight was not included in the analysis. Early sprays were confirmed to be unimportant for early blight, but essential for late blight if early season weather favored disease development. Sprays applied 1 or 2 wk before the end of the season contributed very little to efficient suppression of either disease. Simulation models were used to compare the efficiency of the reduced-sprays strategy and several other methods for suppressing potato early and late blight. In these analyses, the reduced-sprays strategy scheduled two to three fewer sprays, but suppressed early and late blight as well as the other methods. Savings were achieved mainly at the beginning and the end of the seasons. A specific spray-scheduling method for early blight controlled early blight well, but failed to suppress late blight well when there were severe late-blight epidemics. A late-blight-specific spray-scheduling method and a method of scheduling sprays for both diseases suppressed both diseases as well as did weekly sprays (the conventional method) and with the same average number of applications as with weekly sprays.

Additional keywords: Alternaria solani, epidemiology, models, Phytophthora infestans.