Using Diatomaceous Earth (DE) in the Garden
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Gardeners are often given the advice 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 works on other soft-bodied insects, too, including caterpillars and aphids, as well as on 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, it’s recommended to wear eye protection and a dust mask, 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 breathing it in. 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, the same as 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 non-toxic 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 would be 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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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.
I use DIATOMACEOUS EARTH in my chicken coop it helps with the odor and keeps the nasty flys away. Also mix it in the chicken feed as a natural dewormer. I have also dusted the baseboards of our home when we had a flea problem as well as dusting the dog.
Thank you for this article. I see that the recommendation to avoid killing pollinators is to avoid flowers and flower-surrounding leaves, which makes perfect sense. If one practices this, there must be an optimum dilution for aerosol application to minimise damaging pollinators and plants. I see that others have requested this. Is there a recommendation?
I use DE in my garden to get rid of slugs and snails; it works! I also use it to keep cutworms and pillbugs away from tender transplants and seedlings. It works!
However, I always use it as a powder. Will you please inform me of the proper ratio of food-grade DE to water for spray applications?
Thank you!
Please specifically address the issue of food grade DE's effectiveness when wet. One reader posts that she mixed it with water and sprayed. She said it was thus effective. Is it that when it dries it's effective? I've also read that it can be used as a wormer for goats, cats, dogs, etc. by mixing with their food. How does it work for that when the gut environment is wet? I'm confused by seemingly conflicting information. . . . Thank you.
