Copper and substances containing copper are frequently used to fight mildew. It is even permitted in organic farming (even though it can hardly be claimed to be a “natural” treatment). There are now discussions on EU level to declare copper as a not permitted substance in farming, since it is difficult for nature to assimilate it in quantities often used. The irony is that this would perhaps hit hardest for the organic winemakers. Non-organic (“traditional”) grape growing can use alternative, chemical, substances, but organic farmers cannot… The decision is not yet taken though. (Latest news: in a revised list of prohibited substances copper is no longer included, according to our latest information.)
