Farmer adoption and effectiveness of copper-reducing strategies in Swiss viticulture

Copper is widely used in agriculture as an active ingredient in plant protection products. Especially viticulture accounts for the largest share of copper use, primarily to control downy mildew in grapes. Copper use has raised significant environmental concerns, and copper is now classified as a high-risk substance, with phase-out expected in European agriculture. In this study, we analyze data from a pre-registered design involving 489 grape growers in Switzerland to investigate: (i) whether and to what extent growers adopt copper-reducing measures; (ii) the individual measures or combinations of these measures employed; and (iii) which strategies have the greatest potential for copper reduction at the farm level. We find that 57% of copper-using growers adopt some copper-reducing practices. Adoption patterns are highly diverse, with 94 distinct strategies used among 203 growers using copper-reducing measures. Short- and medium-term measures, such as preventive and efficiency strategies, are most frequently implemented. In contrast, substitution and redesign measures—that are often characterized by longer time horizons—are less common. We find that the greatest copper-reduction potential is achieved through integrated strategies combining prevention, efficiency, and redesign measures. We discuss policy implications.