Diatomaceous earth is a a naturally occurring substance formed from fossilized diatoms, a single celled organism with an outer coating containing silica, the primary ingredient in glass. It has numerous uses from filtering to polishing and preventing the caking of animal feed, but the most important to the home gardener may be as an pesticide. Diatomateous earth is found as a sedimentary rock in many places of the world including the US, Canada, and Europe. Most of the deposits of diatomaceous earth date to the Miocene period, about 15 million years ago and are associated with fresh water although some are from saltwater sources.
Ditomaceous earth is crushed or ground into a fine powder which is used as a pesticide because it is able to absorb the waxy coating on the exoskeleton of insects and can cause abrasions to the bodies of mollusks such as snails and slugs. Without an outer covering the animals loose water from their bodies, dehydrate, and often die. As mentioned above, diatomaceous earth can be used in filters and is often used to clean pools but this type diatomaceous earth has been calcinated and is not useful as a pesticide. When buying diatomaceous earth look for “food grade”.
Diatomaceous earth is easy to use but care must be taken avoid contact with the skin and inhaling the powder. It can cause nasal irritation irritation and coughing as well as aggravate existing respiratory problems. Contact with skin or eyes can cause scratching. In spite of these issues, diatomaceous earth is considered a relative safe pesticide. Follow manufacturers instructions to avoid problems.