The field efficacy of six commercial resistance inducers of chemical and natural origin against downy and powdery mildews were evaluated when applied at designated vine growth stages in a mixture with low doses of copper and sulfur, and only when advised by weather-driven disease models. The disease severity and incidence were evaluated for each season at key growth stages (i.e., the end of flowering, berries pea-sized, veraison, and pre-harvest), and areas under the disease progress curves (AUDPC) were calculated and compared with those of nontreated vines. These risk-based applications resulted in a 41% and 61% reduction of interventions against downy and powdery mildews, respectively, compared to the official advice for integrated pest management in the growing area. Overall, when the disease severity was expressed as AUDPC, we observed higher efficacy of all the resistance inducers for powdery mildew, and of laminarin and cerevisane for downy mildew.