Reducing copper inputs through integration of essential oil-based formulations: laboratory and 2-year vineyard evaluation against Plasmopara viticola.

BACKGROUND: Downy mildew of grapevine, caused by Plasmopara viticola, is primarily managed with copper-based fungicides in organic farming, otherwise by preventive treatments with chemical fungicide. However, regulatory restrictions and environmental concerns require strategies that reduce copper inputs, without compromising disease control. Essential oil (EO)-based formulations are emerging as promising alternatives, due to their antimicrobial and antifungal activities. RESULTS: In vitro assays showed dose-dependent inhibition of P. viticola sporulation by the EO-based formulation. The concentration of 500 ppm provided efficacy comparable to the copper standard (67%) with no phytotoxicity. Two-year vineyard trials demonstrated that integrating the EO formulation with reduced copper rates consistently maintained low disease incidence and severity. The copper-EO combination strategy achieved 85% protection on both foliage and clusters, while reducing copper input by 45%. CONCLUSION: Integration of EO-based formulation within reduced-copper spray programs can effectively control grapevine downy mildew under field conditions, without compromising disease control. These findings support the use of EO-based products as viable components of sustainable disease management strategies aligned with current European sustainability policies. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.