The New Student's Reference Work/Mildew

Mil′dew, the name of various plants (fungi), but chiefly applied to a large group of the ascomycetes (which see), which are external parasites growing chiefly upon the leaves of seed-plants and covering the surface like a delicate cobweb. The mildew on lilac leaves is one of the most common forms, this host-plant being very seldom free from it. Apple, cherry and pear mildews are familiar. There are two classes; true or powdery and false or downy mildews. The downy mildews belong to the phycomycetes (which see), and are destructive internal parasites. One of the commonest forms attacks grape-leaves, making its presence known by small, downy patches which come to the surface and consist of minute branches bearing spores. Dusting with sulphur is recommended for plants affected by powdery mildew; and spraying with a fungicide is used for powdery and for downy mildews.