Additive and synergistic antifungal effects of copper and phenolic extracts from grape cane and apples

Abstract

AbstractBackgroundOrganic 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.ResultsWe developed and produced novel ligninsulfonate‐based grape cane extract (GCE) formulations and an apple extract on a pilot plant scale, including a detailed (poly)phenol characterization by high‐performance liquid chromatography photodiode array mass spectrometry (HPLC‐PDA‐MS). Our GCE formulations alone reduced downy mildew disease severity in greenhouse trials by 29%–69% in a dose‐dependent manner, whereas a standard application of the copper‐based agent alone reached ~56%. When applied together, disease severity was diminished by 78%–92%, revealing a synergistic effect that depended on the mixture ratio. Combining GCE formulations with the apple extract, additive effects were found (80% disease severity reduction).ConclusionThe studied plant extracts are proposed to both substitute for and synergistically reinforce copper fungicides in grapevine downy mildew control. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.