What is Mildew?
Mildew is the generic name for a few types of molds that grow readily on moist surfaces.It grows as a mass of threadlike hyphae and fruiting structures produced by various fungi. Mildew gets its name from a Middle English name mealdew, which means, “spoiled meal”.
As well as causing discoloration and staining, mildew brings with it an unpleasant (and instantly recognisable) odor and can also deteriorate building materials (such as plaster and brickwork). Once it invades your home, it spreads rapidly on surfaces and reproduces itself by releasing airborne spores… the fungal equivalent of seeds.
Commonly seen on plants and vegetation, mildew thrives on organic matter including paper, wood , leather and clothing (although many clean synthetic fibres are immune). Mildew is a thin, usually black, sometimes white, growth produced on many surfaces by molds. Molds that cause mildew flourish wherever it is damp, warm, poorly lighted, an/or where air is not circulated – cellars, crawl spaces, closets; on draperies and rugs in basements, on shower curtains, and on damp clothes.They commonly develop in humid summer weather, especially in houses that are closed. These molds are also likely to grow in a new house because of moisture in the building materials.
Mildew growth can deteriorate wood, paper and leather. It can also live very nicely on paint (it’s favorite is latex), penetrating though the paint’s pores into the wallboard paper or absorbent plaster below. It is often found in bathrooms, kitchens, basements, crawlspaces and even attics… anywhere there is high humidity, low ventilation, and a suitable growing medium. Though heat does accelerate mildew’s growth (why the tropical atmosphere of a steamy bathroom is so attractive), some types can grow and thrive at temperatures near freezing!
Two Varieties of Mildew
There are two families of fungi that are parasitic on living plants. The two families are Peronosporaceae, comprising the downy mildews, and Erysiphaceae, comprising the powdery mildews.
The powdery mildews are called so because of the powdery, cobwebbed pattern that their numerous, white spores produce on the leaves of green plants. They attack green plants, usually those grown in the shade in humid regions. They attack nearly 1,500 varieties of flowering plants including gooseberry, pea, peach, rose, apple, cherry and grape, lilac and hackberry. Attacks of powdery mildew cause curling and withering of leaves and often prevent new shoots on the plant.
Downy mildew is a disease that attacks plants in cool humid regions. The fungus grows from a single fertilized cell called a spore. On the upper surface, pale-green to yellow or brown areas usually develop. When the mildew attacks the top part of a leaf, small spores come out of the breathing pores on the bottom of the leaf. Downy patches of mildew that are white, grey, bluish, or violet generally form on the undersides of leaves in damp weather.
Leaves of plants that are affected by downy mildew often wilt, wither, and die early. Sometimes, stems, flowers and fruits are also are infected. Seedlings may wilt and collapse. Garden plants, bush fruits, vegetables, and certain trees, shrubs, field crops, and weeds are susceptible.
Downy plants attack plants such as grape, cucumber, cabbage, lettuce and onion. It can be avoided by rotating annual flowers and vegetables and by avoiding over watering, overcrowding, and poorly drained soil. Other measures include growing resistant varieties, sowing disease-free seed, removing diseased parts and crop refuse, eliminating weeds, and maintaining balanced soil fertility. The application of copper is effective against many downy mildews, but the amount of residue on vegetables must be taken into consideration. Sometimes plants are sprayed with a solution of copper sulphate and lime in water.
Clothes and books
Mildew is a serious problem in damp tropical countries. It can attack clothes, unless they are kept dry. In temperate countries, clothes, if kept wet for too long, are susceptible to being attacked by mildew. Books kept in damp or poorly ventilated places also fall prey to attacks of mildew. There are chemical solutions that may be used to prevent mildew from attacking bookbinding, but many of the solutions are poisonous and should be used with caution and care.
Asthma sufferers and people with certain allergies may also suffer more serious health consequences as a result of mildew in their home.