One such poison is the Bordeaux

One such poison is the Bordeaux

One such poison is the Bordeaux

You see, then, that fungi are living plants that grow at the expense of other plants and cause disease. Now if you can cover the leaf with a poison that will kill the spore when it comes, you can prevent the disease. One such poison is the Bordeaux (bôr-dō') mixture, which has proved of great value to farmers.

Since the fungus in most cases lives within the leaves, the poison on the outside does no good after the fungus is established. The treatment can be used only to prevent attack, not to cure, except in the case of a few mildews that live on the outside of the leaf, as does the rose mildew.