Nanoencapsulation of Plant-Derived Antifungals in Chitosan Oligomer Carriers Reduces Gray Mold Severity in ‘Tempranillo’ Vineyards: Field Efficacy and Preliminary Wine Sensory Assessment

Gray mold (Botrytis cinerea Pers.) is a primary yield-limiting disease in European viticulture. Here we report a field evaluation of two chitosan oligomer (COS)-based nanocarrier (NC) systems loaded with Rubia tinctorum (NC-Rt) and Uncaria tomentosa (NC-Ut) extracts for B. cinerea management in ‘Tempranillo’ vineyards (D.O.P. Ribera del Duero, 2024 season). In vitro, nanoencapsulation reduced the effective extract concentration required for complete inhibition of B. cinerea mycelial growth by 1.8–6.7-fold relative to free extracts. Ex situ, both NC formulations at MIC×3 significantly reduced gray mold severity on inoculated ‘Tempranillo’ bunches at days 5 and 7, but not on ‘Verdejo’ bunches. In a field trial under commercial-vineyard conditions, NC-Ut and NC-Rt reduced mean gray mold severity from 80% in the untreated control to 18–25%, compared with 35–40% for the free extracts and commercial chitosan, an effectiveness of 69–78%. No visual symptoms of acute phytotoxicity were observed during the trial, and cluster weight and cluster number did not differ significantly among treatments. A preliminary, exploratory sensory screening of the wines produced from the treated grapevines detected no significant treatment-related differences in off-flavor or Botrytis-related defect scores. These single-season results support further evaluation of COS-based NCs as delivery systems for plant-derived antifungals in viticulture.