Diatomaceous earth: how it works on pests

Last updated: October 2026

Diatomaceous earth is a powder made from the fossilized skeletons of diatoms, mostly amorphous silica¹. It is not a poison and does not have to be eaten: it kills insects by absorbing the oils and fats from their outer cuticle so they dry out, and its sharp edges speed that process¹. It stays effective only while it is dry and undisturbed¹.

What is diatomaceous earth?

Diatomaceous earth (DE) is made from the fossilized remains of diatoms, tiny aquatic organisms whose skeletons are made of silica¹. Over long periods these remains built up in the sediment of rivers, lakes and oceans, and the deposits are now mined¹. Most DE is amorphous silicon dioxide, though it can contain very low levels of crystalline silicon dioxide¹.

The first pesticide products containing DE were registered in 1960 to kill insects and mites¹. Today over 150 products are registered for use inside and outside buildings and on farms, gardens and pet kennels, mostly as dusts, with some wettable powders and pressurized liquids¹. Their labels list pests such as bed bugs, cockroaches, crickets, fleas, ticks and spiders¹.

In North America, interest in diatomaceous earth peaks in May, as slugs and early garden pests appear, but spring rain, irrigation and dew quickly make outdoor dust barriers ineffective. In the Southern Hemisphere, the same window falls around November.

How does diatomaceous earth kill insects?

DE works physically. It absorbs oils and fats from the cuticle of the insect's exoskeleton, so the insect dries out and dies, and its sharp, abrasive edges speed up the process¹. Researchers describe the same mechanism as abrading or adsorbing lipids from the insect's outer waxy layer, leading to desiccation, and note that DE is more effective at low relative humidity⁵.

Humidity matters because the whole effect depends on drying the pest out. In a laboratory study on poultry red mites, all the inert dusts tested killed mites, but every product was significantly less effective at 85% relative humidity than at 75%⁶. The same study found that surfaces treated with doses much lower than those recommended killed mites within 24 hours of contact as fast as heavy dusting did⁶.

A light exposure that does not kill can backfire. In flour beetles, sublethal DE in the food medium raised net egg production up to 2.1 times control values by suppressing egg cannibalism, and undisturbed cultures reached higher population densities than untreated ones⁵.

Does diatomaceous earth work on garden pests?

Sometimes, and mainly in dry spots. For slugs and snails, UC IPM reports that a band of dry DE 1 inch high and 3 inches wide around the garden can be effective, but such barriers lose their effectiveness after becoming damp, which makes them difficult to maintain and not very useful in most gardens³.

On crops, results vary. In laboratory tests, DE increased mortality of brown marmorated stink bug (Halyomorpha halys) nymphs compared with untreated controls⁷. In pear orchards in 2021 and 2022, DE alone or alternated with sulfur or calcium polysulfide gave stink bug control similar to farm programs based mostly on a neonicotinoid in one orchard, but lower control than that program in another⁷. The same study found that DE, like most products tested, harmed the beneficial egg parasitoid Trissolcus japonicus⁷.

Indoors, DE does best where it stays dry. UC IPM notes that inorganic dusts, including DE, remain effective indefinitely in dry locations against silverfish, but if the deposit gets wet and then dries, it cakes and insects can no longer pick it up⁴.

What does food grade diatomaceous earth mean?

Food grade DE is purified and can be used as an anticaking material in feed or as a clarifier for wine and beer¹. U.S. FDA rules allow DE in animal feed as an inert carrier or anticaking agent at no more than 2% of the total ration, with limits on lead, arsenic and fluorine⁸. When up to 2% is added to food, DE is generally recognized as safe by the FDA².

That status does not cover pest control. The National Pesticide Information Center explains that food grade products and others not labeled for pest control are not checked for pest control risks, so their risks and effectiveness for that use are untested and unknown². Pest control usually means spreading a more concentrated product indoors, where breathing in the dust is of greater concern². Products evaluated for pest control say on the package that they kill or repel a pest and carry an EPA registration number and a signal word². Choose a product with a pesticide label and follow the product label.

What else is diatomaceous earth used for?

Most products that contain DE are not pesticides. There are thousands of non-pesticide products that contain it, including skin care products, toothpastes, foods, beverages, medicines, rubbers, paints and water filters, compared with over 150 registered pesticide products¹. In feed it serves as a carrier and anticaking agent⁸.

In pest control, registered products are used inside and outside buildings, on farms, in gardens and in pet kennels, against pests such as fleas, bed bugs and cockroaches¹. Some products can be used directly on dogs and cats, so check that a product's label lists the use you intend¹.

What are the risks of diatomaceous earth for people and pets?

The main risk is dust. Breathing DE can irritate the nose and nasal passages, and inhaling an extremely large amount can cause coughing and shortness of breath¹. It can irritate the eyes because it is abrasive, and on skin it can cause irritation and dryness¹. Exposure can also happen if products are left where children or pets can reach them¹.

Silica form matters. Long-term inhalation of crystalline silica is associated with silicosis, chronic bronchitis and other respiratory problems, while the amorphous form that makes up most DE is associated only with mild, reversible lung inflammation¹. Amorphous DE has not been associated with any cancers in people¹.

NPIC advises keeping children, pets and other people away during application, wearing a dust mask, eye protection and long clothing, avoiding easily reached areas, and avoiding fans, vacuums and high traffic spots that kick up dust².