Diatomaceous earth: what it kills and what it harms
Diatomaceous earth kills insects that crawl through it while it is dry, by soaking up the waxy coat that stops them drying out. Once it gets wet it stops working. It cannot tell pests from friends: beneficial insects and bees that pick it up are exposed too. The evidence for slugs is weak, and 'food grade' DE has not been checked for pest-control risks or effectiveness.
Also sold or listed as: DE, diatomite, food grade diatomaceous earth.
At a glance
- Active
- Amorphous silica (fossil diatoms)
- Residue
- Works for as long as it stays dry and undisturbed (NPIC). Rain, dew or watering stops it. The supplier side-effect lists give no figure.
- Caution
- 1 of 6 beneficials
- No data
- 5 of 6 beneficials
What it works on
- EarwigsOn the label pest list. It can only reach earwigs that walk through a dry band of dust, so it suits dry, sheltered spots. We found no extension trial of it.
- Ants (not fire ants)On the label, but the label excludes fire, harvester, carpenter and Pharaoh ants.
- SlugsWeak. The University of Minnesota says it has little effect once it absorbs moisture and is generally not an effective slug deterrent. UC IPM says a dry band 1 in high and 3 in wide (2.5 × 7.5 cm) can work, but that damp makes it hard to maintain and not very useful in most gardens.
- SnailsThe same as for slugs. UC IPM's barrier advice covers both, with the same warning about damp.
- Indoor crawling pestsNPIC lists bed bugs, cockroaches, crickets, fleas, ticks and spiders among the pests on registered DE labels. These are dry indoor sites, where the dust stays dry.
- Leaf-feeding garden pestsAgricultural labels list aphids, beetles, caterpillars and more when DE is sprayed as a wettable powder. The label says to repeat it after rain or when the white residue fades. We found no extension source that recommends it for these.
Effect on beneficials
- Samurai waspFemale wasps kept for 7 days on dried DE residue: 24.7 % ± 13.6 died (21.4 % at 4 days). The mean sits on the 25 % line between safe and caution, and the spread runs well above it, so this is rated caution. Lab contact test; the site's supplier-class thresholds applied to mortality. — Chierici et al. 2025, Scientific Reports 15:4622Caution — moderate, 25–75 %
- Aphidius colemaniNo published rating found for this pairing.No sourced rating
- Encarsia formosaNo published rating found for this pairing.No sourced rating
- Phytoseiulus persimilisNo published rating found for this pairing.No sourced rating
- Amblyseius cucumerisNo published rating found for this pairing.No sourced rating
- Chrysoperla carneaNo published rating found for this pairing.No sourced rating
No data never means safe: treat an unrated pairing as caution and try it on a small area first. See every product side by side →
How it works
DE is the crushed silica skeletons of diatoms, which are tiny aquatic organisms. It is not a poison and does not have to be eaten. It absorbs the oils and fats on an insect's cuticle, and its sharp edges speed that up, so the insect dries out and dies (NPIC).
That only happens while it is dry. NPIC says it 'remains effective as long as it is kept dry and undisturbed'. The University of Minnesota says it has little effect on slugs once it absorbs moisture. In a lab study on bed bugs, a blast of steam cut the kill of a DE-based dust and a silica-gel dust, and months of humid storage cut the kill of the silica gel (Ranabhat & Wang 2020).
It is not selective. Nothing in the way it works spares a ladybird, a ground beetle, a parasitic wasp or a bee that picks up the dust. We found no study on bees. In the one test on a beneficial we found, about a quarter of Trissolcus japonicus wasps kept on dried DE died within a week (Chierici et al. 2025).
Using it
- Buy a registered product
- Only DE with an EPA registration number on the pack has been assessed for pest control. NPIC says 'food grade' DE has not been checked for pest-control risks or effectiveness, and that both are unknown.
- Where it works
- In dry, sheltered places that insects walk through, such as the edges of benches, cracks and the bases of pots. Dust labels give a hand or power duster. Outdoors, it has to be put down again after rain or once it has got damp.
- As a spray
- Some agricultural labels allow DE mixed with water as a wettable powder. It leaves a visible white film, and the label says to repeat it after rain or when the residue fades (Diafil 610, EPA Reg. 73729-1).
- Protect yourself
- NPIC advises a dust mask, eye protection and long clothing, and warns against applying it near fans, vents or busy doorways, which lift the dust. The Diafil label asks for a NIOSH-approved particulate respirator during prolonged exposure.
- Re-entry
- Keep children and pets away while you apply it. The Diafil label says to keep them out of the treated area until sprays have dried. It gives no hourly restricted-entry interval for home use.
Cautions
- Breathing the dust
- Breathing it in irritates the nose, and large amounts cause coughing and shortness of breath. Most DE is amorphous silica, which NPIC links only to mild, reversible lung inflammation. Long-term breathing of the crystalline form is linked to silicosis and chronic bronchitis.
- 'Food grade' is not pest-control grade
- Food-grade DE is generally recognised as safe as an additive in food, at up to 2 %. NPIC points out that pest control means spreading a more concentrated dust around a home, where breathing it in is of greater concern. It has no pest-control label, so it gives no dose and no safety directions.
- Don't use pool-filter DE
- DE is also sold as a filter aid, including for pool filters. Like food-grade DE, it carries no pest-control label, so NPIC's warning about unassessed products applies to it. Some filter-aid DE is calcined, which means heated to 800–1,000 °C (about 1,470–1,830 °F), and that turns much of the silica crystalline: one flux-calcined sample tested at 36 % cristobalite, and the producers' association reports about 60 % crystalline silica in flux-calcined grades (Barbieri et al. 2020). Crystalline silica is the form linked to silicosis.
- Bees and pollinators
- The DE label we read carries no pollinator statement. But DE acts on any insect that picks up the dust, so keep it off open flowers and off plants that bees are visiting.
- Pets
- Pets can be exposed if they can reach treated areas, so keep them away while you apply it, and remember they explore close to the floor (NPIC). Some DE products are registered for use directly on dogs and cats, so only follow a label that says so.
- Fish and wildlife
- NPIC calls DE practically non-toxic to fish and aquatic invertebrates. The label still says not to apply it to water.
- Plants
- The labels we read carry no plant-injury warning. The wettable-powder label says only that a visible white residue will stay on treated surfaces.
Use instead
- Slugs and snails: iron phosphate bait, hand-picking and traps. See slugs and snails, and leave the ground beetles that eat them unharmed.
- Aphids, mites and whiteflies on leaves: insecticidal soap or horticultural oil. Each kills only what it wets and leaves little residue.
- Fungus gnats in pots: a Bti drench or Steinernema feltiae nematodes. See fungus gnats.
- Earwigs: see earwigs before you treat. They also eat aphids and insect eggs.
Other products
Sources
NPIC, Diatomaceous Earth General Fact Sheet (Bunch et al., 2013)
NPIC, Is 'food grade' diatomaceous earth okay for pest control? (FAQ)
EPA label, Diafil 610 (Imerys), EPA Reg. 73729-1, accepted 18 Aug 2026
University of Minnesota Extension, Slugs (Weisenhorn & Hahn, reviewed 2024)
UC IPM Pest Notes: Snails and Slugs, UC ANR Pub. 7427 (Wilen & Flint)
Chierici et al. 2025, Natural products vs Halyomorpha halys and Trissolcus japonicus. Sci Rep 15:4622
Ranabhat & Wang 2020, Moisture and insecticide dusts against bed bugs. J Econ Entomol 113:1933
Barbieri et al. 2020, Severe silicosis due to calcined diatomaceous earth. Med Lav 111:222
Lu et al. 2017, DE filtration of swimming pool water. J Water Health 15:374
Drafted from the cited sources, then checked claim by claim against those sources on 23 September 2026.
Always follow the label. Labels are legally binding; this page is not.