Chemicals, Bordeaux Mix

A mixture of copper sulfate and quicklime used as a fungicide. It is used in vineyards, fruit-farms and gardens to prevent infestations of downy mildew, powdery mildew and other fungi. It is sprayed on plants as a preventive treatment; its mode of action is ineffective after a fungus has become established. If it is applied in large quantities annually for many years, the copper in the mixture eventually becomes a pollutant.