Mildew

Mildew is a form of fungus. It is distinguished from its closely related counterpart, 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 have been identified as the cause of certain human ailments. In horticulture, mildews are species of fungus in the order Erysiphales, or fungus-like organisms in the family Peronosporaceae. It is also used more generally to mean mould growth. In Old English, mildew meant honeydew (a substance secreted by aphids on leaves, formerly thought to distill from the air like dew), and later came to mean mould or fungus. The term mildew is often used generically to refer to mould growth, usually with a flat growth habit. Moulds can thrive on many organic materials, including clothing, leather, paper, and the ceilings, walls and floors of homes or offices with poor moisture control. Mildew can be cleaned using specialized mildew remover, or substances such as bleach (though they may discolour the surface). There are many species of mould. The black mould which grows in attics, on window sills, and other places where moisture levels are moderate often is Cladosporium. Colour alone is not always a reliable indicator of the species of mould. Proper identification requires a microbiologist or mycologist. Mould growth found on cellulose-based substrates or materials where moisture levels are high (90 per cent or greater) is often Stachybotrys chartarum. "Black mould," also known as "toxic black mould", properly refers to S. chartarum. This species is commonly found indoors on wet materials containing cellulose, such as wallboard (drywall), jute, wicker, straw baskets, and other paper materials. S. chartarum does not, however, grow on plastic, vinyl, concrete, glass, ceramic tile, or metals.