Diatomaceous Earth (DE) is a naturally occurring, soft sedimentary rock crumbled into a fine, white powder. It is derived from the fossilized remains of diatoms, which are microscopic, single-celled aquatic algae. The skeletons are made primarily of silica, giving the powder its unique physical properties. DE is popular as a natural, non-toxic method for controlling pests in home and garden environments.
Understanding the Types and Safety of Diatomaceous Earth
Recognizing the difference between the two main types of Diatomaceous Earth is essential. Food Grade DE is the only type recommended for use in homes and gardens. This grade is composed of amorphous silica and contains very low levels (typically less than 2%) of crystalline silica, making it safe for use around humans and pets.
The second type, Filter Grade DE (sometimes called Pool Grade), is heat-treated through calcination, converting amorphous silica into crystalline silica. Filter Grade DE contains a much higher concentration of crystalline silica (around 60%) and is toxic if inhaled. This type must never be used for pest control; always ensure the product is clearly labeled as “Food Grade Diatomaceous Earth.”
Food Grade DE is chemically non-toxic but is a physical irritant. The fine dust can irritate the lungs, eyes, and skin. Wear a simple dust mask or respirator during application to avoid respiratory irritation. Gloves and eye protection are also recommended.
How Diatomaceous Earth Works
Diatomaceous Earth works by a unique mechanical action rather than a chemical one, meaning insects cannot develop resistance. Under a microscope, the fine powder particles appear as sharp, jagged shards, abrasive to the protective layers of an insect’s body.
When an insect crawls over the powder, the sharp particles cut into its waxy outer exoskeleton. This compromises the protective barrier, causing essential body fluids to leak out. DE simultaneously acts as a desiccant, absorbing oils and fats from the exoskeleton and leading to rapid moisture loss.
The insect ultimately dies from dehydration. For the process to be effective, the powder must remain completely dry, as moisture neutralizes the mechanical action. It works best on crawling insects; it is not effective against flying insects unless they land directly on a treated surface.
Specific Applications for Indoor Pest Control
Using DE indoors requires a light, strategic application to target crawling pests without creating visible piles. A bulb duster or puffer is the best tool for applying a thin, almost invisible layer. Pests like cockroaches, ants, fleas, and bed bugs avoid thick deposits, making a fine dusting more effective for ensuring contact.
Focus application on areas where pests hide or enter the home, such as along baseboards, under sinks, and behind appliances. Dust into cracks and crevices, window sills, and utility entry points. For flea infestations, lightly sprinkle a fine layer over carpets and pet bedding.
The powder should be left in place for several hours or days. Afterward, the area must be thoroughly vacuumed to remove the powder and dead insects. Since DE is abrasive and can damage some vacuum cleaners, using a low-cost vacuum or one with a simple bag system is advisable for cleanup.
Specific Applications for the Garden
Diatomaceous Earth provides a physical barrier and treatment method against common garden pests like slugs, snails, aphids, and squash bugs. For ground-level pests, the most effective method is creating an unbroken physical barrier on the soil. Spread a continuous ring of the fine powder around the base of individual plants to deter slugs and snails.
For pests feeding on leaves, such as aphids, the foliage can be lightly dusted using a dry application. A handheld duster should coat the upper and lower surfaces of leaves, ensuring the powder is fine and not clumped. Reapplication is necessary after any rain or heavy dew because moisture renders the DE ineffective.
Protecting beneficial insects and pollinators is important, as they are susceptible to the powder’s mechanical action. To minimize harm, apply DE only when they are not actively foraging, typically in the late evening or early morning. Avoid dusting the flowers themselves, where pollinators make direct contact.