Use of Innovative Compounds to Manage Grapevine Downy and Powdery Mildews: Results of a Three-Year Field Trial

Induced resistance (IR) based on elicitors application aims to strengthen plant defenses, rather than directly targeting pathogens. These compounds are less toxic than conventional pesticides and are useful in reducing their use. Strategies based on COS–OGA, Swinglea glutinosa, and low copper doses were tested in this three-year (2021–2023) field investigation against grapevine downy (DM) and powdery (PM) mildew. Their effectiveness was compared to copper, sulfur, untreated, and water-sprayed plants in a naturally infected vineyard. Combined treatments provided higher levels of protection. COS–OGA at 2 L ha−1 combined with low copper doses and an adjuvant protected canopy and production from both DM and PM at the same level as copper and farm application (based on copper and sulfur). In favorable seasons, 2023 for DM and 2022 for PM, this strategy reduced the DM McKinney Index compared to untreated plants by 74% and 39% on leaves and bunches, respectively. Reductions observed for PM were 85% on leaves and 46% on bunches. S. glutinosa showed reductions only in one assessment against PM on bunches. This work validates IR-based DM and PM management strategies under field conditions and paves the way toward concrete reduction in copper and sulfur use in vineyards.