This article is part of our Organic Pest Control Series, which includes articles on attracting beneficial insects, controlling specific garden pests, and using organic pesticides.
What Is Diatomaceous Earth?
Diatomaceous earth (DE) is a powder made from fossilized prehistoric crustaceans called diatoms. The sharp edges of DE cut into insects’ bodies, causing them to die of dehydration. Diatomaceous earth is most useful in dry situations — for example, puffing it into crevices where cockroaches have been seen. In the first few days after their habitat is treated, cockroaches may become more visible as they desperately search for water, but will die within two weeks. DE becomes less effective when wet, yet still can be used in the garden to make life difficult for newly emerged Japanese beetles or cutworms. In dry weather, DE spread beneath plants will kill slugs.
DE makes an excellent filter material and has numerous industrial uses. When buying DE to use around your house, be sure to buy a product listed as “food grade.”
Which Pests Does Diatomaceous Earth Control?
Most indoor invaders, including roaches, silverfish, spiders and even fleas are impacted by DE. Including DE in chickens’ dust bath mixture helps prevent problems with lice. Diatomaceous earth also has many uses around the homestead, as it can help control fleas on dogs and to reduce parasites in horses, pigs and other animals.
How to Use Diatomaceous Earth
Lightly sprinkle dry DE on the soil’s surface where slugs, newly emerged Japanese beetles, or other unwanted pests will come into direct contact with the dry particles. Renew after rain or heavy dew.
Indoors, use a bulb puffer to blow DE into crevices where bugs are likely to hide. You also can puff DE onto newly hatched larvae of many pests, including squash bugs, Mexican bean beetles or Colorado potato beetles.
To be effective, the insects must be well coated with the dust. Honeybees and other beneficial have no way to protect themselves from the mechanical effects of DE. When applying DE to plants that are likely to be visited by bees, cover them with an old sheet after treatment so the DE will target pests and the bees can’t get to the plants. Later, uncover the plants, and then wash off the DE with a fine spray of water.
How to Store Diatomaceous Earth
Store DE products in their original containers on a high shelf, out of the reach of children and pets, in a dry place. When stored in an airtight container and kept dry, DE has an indefinite storage life.