mildew

thumb|Example of downy mildew (left) along with [[powdery mildew (right) on a grape leaf]]

Mildew is a coating of fungal or oomycete growth on plants or other surfaces. It is distinguished from the closely related mould largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consisting of minute hyphae (fungal filaments) produced especially on living plants or organic matter such as wood, paper or leather. Both mould and mildew produce distinct offensive odours, and both are the cause of human ailments.