Winegrowers all over France, yes, all over the world, organic as well as conventional, spray the vines with copper against the severe fungal disease downy mildew (mildiou).
There are, regretfully, very few realistic alternatives to copper. In fact, only a tiny part of the French vineyard surface is not sprayed with copper at all, around 14%. These vineyards are located mainly in a department called Gers in the Southwest. Here we find, for instance, the large Plaimont cooperative with 800 members and 5,300 hectares. Many of the wines are the popular IGP Côtes de Gascogne made from the aromatic grape varieties sauvignon blanc and colombard.
Copper spraying on aromatic vines and can cause a particular problem. If there is copper left in the must (in tiny quantities, not dangerous for humans) after pressing the grapes, it can prevent the development of thiols, compounds that are responsible for certain aromatic characteristics in the wine.
Plaimont recommends that its members preferably not use copper at all or at least not in the last 5–6 weeks before harvest. This presupposes that you work conventionally and instead use chemical synthetic products. That is not possible if you work organically.
Read more: Vitisphere
