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 held 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 signihcantly (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