Mildew is a disease in which the pathogen is seen as a growth on the surface of plants. The same word is used for the fungus causing the disease. Mildews are Ascomycetes. Black mildews are parasites in the order Meliolales with a dark mycelium to give a sooty effect. They are common in the South or on tropical plants in greenhouses (Black Mildew). Powdery mildews are plant parasites in the order Erysiphales. They have white mycelium, in a delicate weft or thick felt, made up of a criss-cross tangle of hyphae. Colorless spores borne in chains on upright conidophores give the white powdery effect (see Fig. 1). False or downy mildews are oomycetes, and the conspicuous growth is not vegetative mycelium but fruiting structures and conidia protruding through stomata or epidermis to give a white frosty appearance in moist weather (Downy Mildews).