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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I live in Central Texas and I have been using diatomaceous earth in my garden for several years now, especially when I plant my potato sets. For years, I would have a fire ant mound with almost every potato plant at harvest time and the potatoes themselves would be covered with fire ant bites. Now, I put DE in every hole at planting time, put the potatoes in and then put a dusting of DE on top of the potatoes before I cover them with dirt. The fire ant problem is now gone and no more fire ant bites on the potatoes!!! I even use DE when I plant my squash and some other things to keep bugs away from the roots.
If you're encouraging Monarch butterfly visits, D.E. is harmful to butterfly larvae (caterpillars) and other beneficial insects.
Can I put my chicken droppings with food grade DE in my compost?
You can certainly make compost with chicken poop; just make sure it’s properly aged (2 months or so) before adding to a food garden. You can also sprinkle food DE onto your compost which helps with pests. DE does not harm earthworms; they can actually eat it. Many worm farmers sprinkle DE on the surface of their worm bins to control fruit flies and fungus gnats.
Would you recommend using this in a chicken coop or for dust baths?
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.
