The no-copper challenge to control Downy mildew of grapevine based on a clove oil formulation

Despite the limitation of the copper use by the European Union due to its dangerous accumulation in soil, cupric fungicides remain the primary plant protection products for controlling grapevine downy mildew (Plasmopara viticola), particularly in organic viticulture. This study investigates the efficacy of ND24_55, a novel formulation based on carbonated hydroxyapatite and clove oil, as a sustainable alternative. Results from in vitro, in vivo, and in planta experiments under controlled conditions confirmed the formulation's ability to control the oomycete through both preventive and curative strategies. This efficacy is attributed to a direct inhibitory effect on zoospore release and germination, alongside biostimulant and priming effects that vary based on the application dose. Although a transient impact on photosynthesis was observed, the formulation effectively suppressed disease development. These findings suggest that ND24_55 could represent a viable biopesticide candidate for grapevine protection, with future research necessary to evaluate its performance under vineyard field conditions.