Though molds are always present in the air, those that cause mildew need moisture and certain temperatures in order to grow. They commonly develop in humid summer weather, especially in houses that are closed. They grow fastest at temperatures between 75 F. and 85 F. Sunlight helps kill mildew. These molds grow on anything from which they can get enough food. In homes they develop most often on cotton, linen, rayon, silk, wool, leather, wood, and paper.
Many synthetic fibers are resistant to mildew.
These molds are also likely in a newly built house because of moisture in the building materials. This article was written by Anne Field, Extension Specialist, Emeritus, with reference from the USDA bulletin, Mildew. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information becomes public property upon publication and may be printed verbatim with credit to MSU Extension.