Diatomaceous Earth (DE) is a naturally occurring, fine white powder derived from the fossilized remains of ancient, single-celled organisms called diatoms. These skeletal remains form a soft, sedimentary rock that is milled into the powder. DE has become a popular, non-chemical option for controlling various insect pests in homes and gardens. Unlike synthetic pesticides, DE works through a physical process, making it a favored tool for integrated pest management strategies.
Understanding Diatomaceous Earth
DE functions as a mechanical insecticide, killing insects physically rather than chemically. Under a microscope, the fine powder consists of razor-sharp, microscopic edges of silica. When an insect crawls across the powder, these edges scratch and pierce the protective waxy layer of the exoskeleton. This abrasion compromises the insect’s defense against moisture loss.
The highly absorbent silica then draws moisture and oils from the insect’s body, leading to death by desiccation. This process typically takes a few hours to a day or two and requires direct contact with the powder to be effective. Since the killing action is mechanical, insects cannot develop a resistance to Diatomaceous Earth over time.
Not all Diatomaceous Earth is suitable for pest control, and differentiating the grades is important for safety. Filter Grade DE is chemically treated and contains crystalline silica, which is highly dangerous if inhaled and should never be used in homes or gardens. Food Grade DE contains predominantly amorphous silica and is the only type approved for use around people, pets, and food sources. When purchasing DE for bug control, confirm the product is explicitly labeled as “Food Grade.”
General Application Techniques
The effectiveness of DE relies on insects walking through it, so the powder must be applied in a thin, nearly invisible film. Insects actively avoid thick, noticeable piles, which renders the application useless. To achieve this fine layer, use specific tools like hand dusters, bulb puffers, or flour sifters. These tools allow for precise control and ensure the powder is distributed lightly across target surfaces.
DE must remain completely dry to function as an abrasive and absorbent agent. If the powder becomes wet, the microscopic particles clump together, losing their sharp edges and absorbent properties. For outdoor applications, DE must be reapplied following rainfall or heavy dew. Indoors, ensure the powder is placed only in dry areas, away from moisture sources.
DE can also be mixed with water to create a slurry for covering plants or hard-to-reach vertical surfaces. A typical mixture involves four tablespoons of DE per gallon of water. The mixture is sprayed onto the target area using a handheld sprayer. The DE is inactive while wet, becoming potent only once the water fully evaporates, leaving behind the thin, dry layer of silica particles.
Targeting Pests in Specific Areas
Indoor Application
For indoor pests like ants, cockroaches, or silverfish, precision is necessary to avoid unnecessary dust in living areas. The powder should be puffed directly into cracks, crevices, and wall voids using a specialized bulb duster. Apply a fine line behind appliances, under sinks, and along baseboards where pests travel to ensure contact without excessive airborne dust. Since DE is non-toxic, it can be used safely in kitchen cabinets and pantries, provided the application is kept light and away from open food.
Garden and Barrier Use
In the garden, DE works as both a direct treatment and a barrier. For treating plants, a very light dusting on the leaves and stems can deter pests like aphids or squash bugs. Focus the application on the underside of leaves where many soft-bodied insects congregate. Care must be taken to avoid covering blooms and potentially harming pollinators.
A continuous, thin line of DE around the perimeter of garden beds or containers creates an effective barrier against crawling pests such as slugs and snails. These barriers should be two to three inches wide to ensure the pest must cross the material to reach the plants. Applying the powder directly to the topsoil ensures it contacts ground-dwelling insects.
Pet and Animal Housing
DE is frequently used to manage external parasites on pets and in animal housing. For treating fleas and mites in pet bedding, a light dusting can be worked into the fibers and left for several hours before vacuuming. In chicken coops or livestock stalls, the powder can be spread on the floor and worked into litter to control mites and lice. When dusting an animal’s coat for fleas, gently rub the powder into the fur, carefully avoiding the animal’s eyes and nasal passages to prevent irritation.
Safety Precautions and Storage
While Food Grade DE is chemically safe, the primary safety concern during application is inhalation. Any fine dust can irritate the lungs and respiratory system, especially in individuals with breathing sensitivities. Wearing a simple dust mask or a respirator when applying the powder, particularly in large or enclosed spaces, is a necessary precaution.
The abrasive and moisture-absorbing nature of DE can also cause minor irritation upon contact with skin or eyes. If the powder gets into the eyes, flush them immediately with water; consider wearing safety glasses during application. Because the powder is highly drying, wash hands and apply moisturizer after handling the material.
To maintain efficacy, DE must be stored in a sealed, waterproof container in a dry location. Keeping the product dry ensures that the silica particles retain their sharp structure and absorbent properties over time. Always ensure the storage container is clearly labeled “Food Grade” to prevent confusion with industrial grades.