Diatomaceous Earth (DE) is a naturally occurring, soft, powdery rock composed of the fossilized remains of diatoms, which are microscopic aquatic organisms. These fossils are primarily made of silica, giving the powder its unique properties. Understanding the type of DE is important before household use.
The market offers two primary grades: Food Grade and Filter Grade. Food Grade DE contains amorphous silica and less than 1% crystalline silica, making it suitable for use around people, pets, and food. Filter Grade (or Pool Grade) DE is heat-treated (calcination), which significantly increases the crystalline silica content, making it unsafe for non-industrial use and toxic if ingested. For any home, garden, or pet application, you must only use certified Food Grade Diatomaceous Earth.
Home and Garden Pest Management
Diatomaceous Earth is effective against many insects because of its mechanical, non-chemical mode of action. The powder consists of microscopic, sharp edges that pierce the waxy, protective outer layer (epicuticle) of an insect’s exoskeleton.
Once the cuticle is compromised, the highly absorbent silica rapidly draws out moisture and essential body fluids. This dual action of abrasion and absorption leads to death by desiccation. Since the mechanism is purely physical, insects cannot develop resistance to DE, unlike chemical pesticides.
For managing crawling pests indoors, apply a very thin layer along baseboards, under sinks, and in cracks where pests travel (e.g., ants, fleas, and cockroaches). When treating for fleas, lightly dust carpets and pet bedding for a few hours before vacuuming. In the garden, dust the foliage of plants to control soft-bodied pests like aphids and mites.
DE can also be used to create physical barriers around vulnerable plants to deter slugs and snails. This pest control method is only effective when the powder remains dry. In the garden, the material must be reapplied after heavy dew or rain to maintain efficacy.
Practical Household Applications
DE’s highly absorbent and mildly abrasive nature makes it useful for various household tasks. The powder is excellent at absorbing moisture and neutralizing odors. A small, open container of DE placed in a refrigerator or a light sprinkle in the bottom of a trash can helps eliminate smells.
It can be used as an additive for cat litter to absorb liquids and odors. For cleaning oil or grease spills on garage floors or driveways, sprinkle a generous amount of DE onto the liquid. Allow it time to soak up the mess before sweeping it away, which makes cleanup easier.
The fine powder can be mixed with water to create a mild scrubbing paste for non-scratch cleaning. This paste is useful for polishing metal objects, such as silverware, or for gently scouring sinks and tubs. The powder acts as a gentle exfoliant, lifting grime without damaging surfaces. Applying a thin dusting to mattresses and upholstered furniture before vacuuming can also help deodorize and absorb moisture.
Safe Handling and Application Techniques
While Food Grade DE is non-toxic, it is a very fine powder that requires careful application. The most important precaution is to avoid inhaling the dust, as the particles can cause irritation to the lungs and nasal passages. Wearing a dust mask or respirator and eye protection is recommended during application, especially in enclosed spaces.
The powder is most effective when applied as an almost invisible layer. Insects are more likely to walk through a fine film than a thick pile, and applying too much DE often causes pests to navigate around the treated area, reducing efficacy. A bulb duster or similar tool is useful for applying the powder lightly and uniformly into cracks and crevices.
DE can be mixed with water to create a slurry that can be sprayed onto surfaces, such as the sides of a shed or the base of plants. This method prevents airborne dust. However, the DE will not be insecticidally active until all the water has evaporated and the powder is completely dry again. Since moisture deactivates the material, dry application is usually preferred indoors, and reapplication is necessary outdoors after rain or watering.