Incorporation of Cultivar Resistance in a Reduced-Sprays Strategy to Suppress Early and Late Blights on Potato. D. SHTIENBERG, Department of Plant Pathology, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet-Dagan 50250, Israel. R. RAPOSO, S. N. BERGERON, D. E. LEGARD, A. T. DYER, and W. E. FRY, Department of Plant Pathology, 334 Plant Science Building, Cornell University, Ithaca, New York 14853. Plant Dis. 78:23-26. Accepted for publication 11 September 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0023.

Predictions from simulation analysis concerning the relative contributions of host resistance and protectant fungicide in a reduced-sprays strategy to suppress potato early and late blights were examined in field trials. As predicted, disease-induced defoliation in cultivars moderately resistant to both diseases, sprayed on a 14-day schedule, was not significantly different (P = 0.05) from defoliation in a susceptible cultivar sprayed on a 7-day schedule. Evaluation of the reduced-sprays strategy using cultivars of different resistance indicated that disease in plots treated according to the reduced-sprays strategy did not differ significantly (P = 0.05) from disease in plots treated according to the common management practice, although three fewer sprays were applied in the reduced-sprays treatment. Thus, incorporation of host resistance into a reduced-sprays strategy should enable large reductions in the amount of fungicide required for adequate disease suppression.