In last years of 19th century, the bug Phylloxera, imported with North American plants, destroyed almost half of European vineyards. New varieties of American grapes were grafted, more resistant to the insect but also more sensitive to a fungus called mildew (Plasmopara viticola). This new disease rapidly ravaged vineyards. The French botanist Alexis Millardet discovered by chance the protective effect of copper against mildew. Since 1885, vineyards are sprayed with Bordeaux mixture, a preparation of copper sulphate (CuSO4) and slaked lime (Ca(OH)2). Other copper-based mixtures are now available as fungicides for vineyards, fruit trees and ornamental plants.