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Diatomaceous earth (DE) is one of the most popular non-chemical bug killers. It’s a fine powder made from the fossilized shells of tiny algae called diatoms. It works mechanically rather than chemically, but “natural” doesn’t mean “use it carelessly.” Here’s how to buy the right kind and use it well.
How DE kills insects
Under a microscope, DE particles are sharp and highly absorbent. When an insect crawls through it, the powder damages and strips the waxy outer coating that keeps the insect from drying out, and the insect dehydrates over hours to days. Because it’s a physical action, insects don’t develop resistance to it the way they can to chemical insecticides.
Food grade vs. pool grade: the critical difference
| Food grade | Pool / filter grade | |
|---|---|---|
| Processing | Not heat-treated | Heat-treated (calcined) |
| Crystalline silica | Typically under 1% | High (often well over half) |
| Use for pests? | Yes, carefully | Never |
Calcining turns much of the silica into its crystalline form, which can cause serious lung disease when inhaled. Pool-grade DE belongs only in a pool filter. The color won’t tell you which is which; the label will.
Check price for food-grade diatomaceous earth →
Check price for a bulb duster applicator →
What DE works on
- Ants, along travel paths and in wall voids
- Cockroaches, behind and under appliances
- Fleas, worked lightly into carpet, then vacuumed after a few days
- Silverfish, earwigs and crickets
- Garden pests like slugs, when dry. It can also harm beneficial insects, so don’t dust flowers bees visit.
A note on bed bugs: the EPA advises that if you use a desiccant dust for bed bugs, it should be one registered by the EPA and labeled for bed bug control. Food-grade and pool-grade products aren’t intended for that use. See our bed bug guide.
How to apply DE the right way
- Wear a dust mask and keep kids and pets out of the room.
- Use a bulb duster to puff a barely visible film. Insects walk around thick piles but straight through thin dust.
- Target hidden, dry spots: cracks, baseboard gaps, behind the fridge and stove, under sinks, wall voids and outlets (with the cover off and power off).
- Let it work for several days. DE is slower than sprays.
- Clean up visible dust from open floors with a vacuum (a shop vac with a fine filter is best), and reapply in hidden areas as needed.
- Reapply outdoors after rain or watering. DE stops working when wet.
Common mistakes
- Dumping thick piles on the floor
- Applying it in damp areas like under a leaky sink, where it clumps and stops working
- Puffing it into the air in an occupied room
- Buying pool grade because it was cheaper
Follow product label directions. Products sold specifically to kill insects must carry pesticide labeling; follow it.