Copper in organic viticulture: the limits, the maths and how to stay under them

Copper is the organic grower’s main weapon against downy mildew — and its biggest regulatory constraint. It does not break down; it accumulates in the soil, so its use is capped. Staying compliant means tracking not the product you sprayed, but the metallic copper it contained, per hectare, over years.

The limit is metallic copper, per hectare, over time

In EU organic production, copper is limited to 28 kg of metallic copper per hectare over a rolling 7-year period — which averages 4 kg/ha per year, though it can be front-loaded within the seven-year envelope. Individual member states and certification bodies may set stricter annual caps, so your local rule can be tighter than the EU ceiling.

The limit is on metallic copper, not on product. A copper fungicide is only part copper — you must convert every application to its metallic-copper content to know where you stand.

Doing the maths from the label

Each copper product declares its copper content. Bordeaux mixture is roughly 20% metallic copper; copper hydroxide and copper oxychloride formulations differ. To find the metallic copper applied, multiply the product mass by its copper fraction, then divide by the treated area.

• Metallic Cu applied (kg) = product (kg) × copper fraction.
• Per hectare = metallic Cu ÷ treated area (ha).
• Sum per block across the season, then across the rolling 7 years.

Spraying smart to spend less copper

• Time by risk, not calendar — a weather-driven model avoids sprays that a dry spell makes unnecessary.
• Protect before the rain — copper is preventive, so well-timed cover does more with less.
• Combine with canopy management and resistant cultural practices to lower disease pressure.

The field notebook is your proof

The 7-year copper budget is only credible if every application is recorded with its product, copper content and treated area. GrapeFlow logs each spray against the block and the physical product batch, so the running metallic-copper total per hectare is a report, not an end-of-inspection panic.

This is a practical overview, not legal advice. Confirm the current copper limits with your certifier and national rules — they can be stricter than the EU ceiling.