LAUSR

BACKGROUND Organic viticulture seeks sustainable alternatives for eco-toxic copper fungicides to control downy mildew caused by Plasmopara viticola. (Poly)phenol-rich extracts of agricultural byproducts are known to possess antifungal activity, but high production costs often limit their actual implementation. RESULTS Herein, we developed and produced novel ligninsulfonate-based grape cane extract formulations and an apple extract on pilot plant scale, including a detailed (poly)phenol characterization by HPLC-PDA-MS. Our grape cane extract formulations alone reduced downy mildew disease severity in greenhouse trials by 29-69% in a dose-dependent manner, while a standard application of the copper-based agent alone reached ca. 56%. When applied together, disease severity was diminished by 78-92%, revealing a synergistic effect that depended on the mixture ratio. Combining grape cane formulations with the apple extract, additive effects were found (80% disease severity reduction). CONCLUSION The studied plant extracts are proposed to both substitute for and synergistically reinforce copper fungicides in grapevine downy mildew control. This article is protected by copyright. All rights reserved.