Mildew is a form of musty odor.
Mildew requires certain factors to develop. Without any one of these, it cannot reproduce and grow. The requirements are a food source (any organic material), sufficient ambient moisture (a relative humidity of between 62 and 93 percent), and reasonable warmth (77 °F (25 °C) to 88 °F (31 °C) is optimal, but some grown can occur anywhere between freezing and 95 °F (35 °C)). Slightly acidic conditions are also preferred. At warmer temperatures, air is able to hold a greater volume of water; as air temperatures drop, so does the ability of air to hold moisture, which then tends to condense on cool surfaces. Ironically, this can work to bring moisture onto surfaces where mildew is then likely to grow (such as an exterior wall). Preventing the growth of mildew requires a balance between moisture and temperature either in such a way that minimal moisture is available in the air and the air temperature is low enough to inhibit growth (at or below 70 °F (21 °C) without causing condensation to occur, or by in such a way that warmer air temperatures, without an actual change in the amount of water vapor in that air, is by its nature "drier" (has a lower relative humidity) than cooler air and will tend to inhibit mildew growth in this way. Warm temperatures coupled with high relative humidity set the stage for mildew growth.
Air conditioners are one effective tool for removing moisture and heat from otherwise humid warm air. The coils of an air conditioner cause moisture in the air to condense on them, eventually losing this excess moisture through a drain and placing it back into the environment. They can also inhibit mildew growth by lowering indoor temperatures. In order for them to be effective, air conditioners must recirculate the existing indoor air and not be exposed to warm, humid outside air. Ironically, some energy efficient air conditioners may cool a room so quickly that they do not have an opportunity to also effectively collect and drain significant ambient water vapor.
- mildew: Compact Oxford English Dictionary
- mildew: Merriam-Webster's Online Dictionary, 11th Edition
- The American Heritage Dictionary of the English Language, 1969, entry "melit-" in Appendix
- "Cleaning Mildew from Retractable Awnings". Shade & Privacy. Retrieved 15 September 2014.
- Peart, Virginia (October 2001), How to prevent and remove mildew (PDF), University of Florida IFAS Extension
- SAFECROP - Proceedings of the 5th International Workshop on Grapevine Downy and Powdery Mildew
 The term mildew is often used generically to refer to
Another plant-associated type of mildew is Peronosporaceae (Oomycota). They are obligate plant pathogens, and the many species are each parasitic on a narrow range of hosts. In agriculture, downy mildews are a particular problem for potato, grape, tobacco and cucurbits farmers.
What horticulturalists and gardeners often refer to as mildew is more precisely powdery mildew. It is caused by many different species of fungi in the order Erysiphales. Most species are specific to a narrow range of hosts, and all are obligate parasites of flowering plants. The species that affects roses is Sphaerotheca pannosa var. rosae.
- Plant pathogens 1
- Household varieties 2
- See also 3
- References 4
- External links 5
Horticulturalists classify mildew differently than most other people. In horticulture, mildew is either species of Peronosporaceae. It is also used more generally to mean mold 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 mold or fungus.
Both mold and mildew produce distinct offensive odors, and both have been identified as the cause of certain human ailments.