Using Diatomaceous Earth (DE) in the Garden
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Gardeners are often advised to sprinkle diatomaceous earth (DE) around plants to deter pests. Unsurprisingly, we’re often asked, “What is diatomaceous earth, exactly?” Well, here’s your answer!
What Is Diatomaceous Earth?
Diatomaceous earth (DE) is the fossilized skeletons of microscopic single-celled aquatic organisms called diatoms. Their skeletons are made of a natural substance called silica, which makes up 26% of the Earth’s crust by weight.
Deep deposits of diatomaceous earth are mined in the western United States in places where lakes once covered the area millions of years ago.
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How Does Diatomaceous Earth Deter Garden Pests?
Slugs and snails do not like to crawl over DE because the silica skeletons are very sharp—like tiny pieces of broken glass. (Slugs and snails don’t like eggshells, either!) If their soft bodies do get cut, they eventually dehydrate and die. This process also works on other soft-bodied insects, including caterpillars and aphids, and those with hard shells, such as beetles, fleas, cockroaches, and even bed bugs. The tiny particles of DE get into the insects’ joints, causing irritation and dehydration.
Caution: The downside to DE is that it does not discriminate between pests and beneficial insects. Ladybugs, green lacewings, butterflies, bees, and other “good guys” can also be killed by DE if they come into contact with it. For this reason, we recommend using DE with discretion on and around plants that beneficial insects may frequently visit. Avoid using it around flowers as well.
How to Use DE
- When shopping for DE, look for “food grade” quality. The DE used in pool filters is not effective against garden pests.
- Sprinkle bands of DE around the plants you are trying to protect. It’s important that the ring of DE does not have any gaps for pests to sneak through.
- If pests are eating the leaves of your plants, you can dust the leaves with DE, which should discourage further damage. However, you should avoid applying DE near the plants’ flowers, where pollinators might inadvertently come into contact with it.
- When using DE, wearing eye protection and a dust mask is recommended, as the small particles can be irritating.
- DE works best in dry conditions. It clumps together when wet, so reapply after it rains.
Is DE Safe to Use? Is it Toxic?
Even though the industry states that this product does not cause lung damage, I would still refrain from inhaling it. Remember, it might feel soft to the touch, like talcum powder, but it still is an abrasive and can cause irritation to your eyes, nose, lungs, and throat. Wear a dust mask and eye protection when handling it just to be on the safe side.
Food-grade DE is not toxic if ingested in small quantities. In fact, we probably have been eating it unknowingly for years since it is often mixed with grain in storage to kill insects. It can also be found in toothpaste and skin care products. Some people take it a step further and use it to treat internal parasites! However, the DE commonly used in pool maintenance is not edible.
DE does not harm the soil since it is made from silica, like sand and many rocks. It does not break down when exposed to the sun. Rain can wash it into local water sources, but it is nontoxic to fish and other aquatic life. It is not harmful to birds or other wildlife. It has been added to livestock feed for years.
If pests are enough of a problem that you’re tempted to resort to a chemical pesticide, give DE a try first. It is considered organic by the Organic Materials Review Institute (OMRI), and the National Organic Program considers it a non-synthetic and permits its use in crop production.
See the Almanac’s Pests and Diseases Library for more advice on solving gardening problems.
Have you ever used DE in the garden? Tell us about your experience in the comments below!
Robin Sweetser
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Do not use for a dust bath. You don’t want to be breathing in dust. However, diatomaceous earth is used in the chicken coop by owners to keep it mite- and lice-free. When you apply, wear a face mask if you are sensitive to dust. First, clean out all the old bedding, then sprinkle it on the floor and bottom of the nesting boxes. Let the dust settle and then put fresh bedding on top. You can also feed DE to chickens to prevent internal worms. The ratio is 2 percent diatomaceous earth in the feed you give them. Always make sure it’s FOOD-grade DE.
From what I have read, no. DE can irritate the lungs and since birds stir up lots of dust while taking a dust bath, they can breathe in the DE, causing health issues.
However, we used DE on our dog when she was a puppy to keep her flea and tick free and it seems to have worked without any adverse effects. Of course, we sprinkled it onto her tummy and rubbed it into her fur so she wasn't breathing it in. Plus, dogs are not nearly as fragile as birds and have more mass than most birds, so they can withstand more physical stress.
I am not a vet, just a bird, dog and cat owner. Your mileage may vary but I won't risk it with my chickens and Guinea fowl.
I Have sprinkled about 3 inches wide of diatomaceous earth around the perimeter at the base of my house to stop the carpenter ants. They used to climb up to my roof and ceilings. I also put it under and around my wood pile. I works great.
Never had this problem before: I have big black ants 1/2" interfering with my okra set. They get on the base of the flowers and the flowers can abort the fruit or disfigure the pods. Will diatomaceous earth at the base of plants keep them off?
If you have gnats flying around your house and can't figure out where they're coming from and have indoor potted plants, try this. Just sprinkle it on top of the soil and you will be rid of those pesky gnats. Fungus gnats lay their eggs in the soil and then hatch out and the cycle goes on and on. I also use it on my four dogs as a natural flea powder, works great.
Will DE harm all the earthworms in my garden? I always have a problem with slugs and cabbage worms in the spring and squash bugs on my zucchini. I would like to try DE but have always been hesitant.
I have used Food Grade DE many times on the Feral Cats I feed. There's a patch of dry dusty dirt close to where I feed them. I sprinkle DE on the ground & then add a bit of Catnip & they roll in it. Covering themselves with DE to kill Fleas! They are all Black Cats & look Hilarious covered in White Dust! I also mix it into their food to help with Parasites! I sprinkled it on my Carpet & brushed it in when I was Fostering a Feral Mama & her Kittens in my spare bedroom. No Fleas got past that room!
This article states that DE is edible. FOOD GRADE DE is edible. The stuff used in your pool IS NOT! Pool Grade is heat-treated to make it a better filtering agent. It also turns the silicone dioxide in the DE to crystalline silica, which CANNOT be eaten!
Yes, you are correct! We’ve made this more clear in the article.
