Reducing Copper Use in Viticulture: Combining Measures Delivers the Greatest Impact

Copper is widely used in Swiss viticulture—but is increasingly under pressure due to environmental risks. A new study by ETH Zurich shows how its use can be reduced. Which measures make the difference?

Copper-based fungicides are a key element of plant protection in both organic and conventional viticulture, particularly for controlling downy mildew. At the same time, copper is considered environmentally critical due to its persistence in soil and its negative effects on soil organisms. In Switzerland and the EU, its use is therefore under increasing regulatory pressure, with the aim of reducing risks and establishing long-term alternatives.

Highly heterogeneous approaches to copper reduction

A survey conducted by ETH Zurich among 489 organic and conventional wine-growing farms across all Swiss language regions shows that 73% of farms use copper-based fungicides. Of these, 57% already apply explicit measures to reduce copper use. However, implementation is highly heterogeneous: a total of 94 different strategies were identified, most of them combining several measures. Single measures play only a minor role.

The most used approaches are short-term efficiency and preventive measures, such as adjusted copper dosages, optimized spraying schedules, or canopy management. Substitution approaches (e.g., copper alternatives like calcium carbonate) as well as long-term system changes—for example, the use of fungus-resistant grape varieties—are used significantly less frequently.

Greatest reduction potential achieved through combined strategies

Statistical analysis of copper quantities applied on farms shows that the greatest reduction potential arises from combined strategies. Particularly effective is the combination of prevention, efficiency, and fundamental system redesign measures. On average, this combination enables a reduction of about 0.65 kg/ha/year compared to farms without reduction measures. In contrast, purely substitution-based approaches or isolated measures show no significant effects.

The results also highlight that many farms already operate below legal limits and label thresholds. Nevertheless, the problem remains, as copper accumulates in the soil and has long-term effects. Sustainable reduction therefore requires more than optimizing existing practices; it demands structural changes in production systems, for example using fungus-resistant grape varieties.