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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Has anyone used it for sawflies? From what I have read, the sawfly larvae emerge in the spring from the earth (typically) underneath the trees. Sawflies are devastating our Blue Spruces. My hope is DE kills the larvae. This is the 2nd year we will try DE, but I would love any feedback.
Hi Susan,
Sorry to hear about the issues with your blue spruces. Sawfly larvae typically emerge in the spring/early summer, depending on what type they are.
Diatomaceous earth can be used to help with sawfly larvae. When insects/larvae crawl through it, diatomaceous earth damages the outer layer of their bodies and will kill them quickly.
You will want to spread it around the base of your plants when you see the first signs of them, but since it is a powder, it will need to be reapplied after it rains or during humid weather.
You can also apply it to the directly to the plant as a secondary approach.
Hope this helps! And good luck with getting rid of you pest issue.
IT WORKS AS A FLEA KILLER ON DOGS & FOR LICE ON CHICKENS WE USED IT ON OUR SHOWDOGS FOR YEARS I GUESS IT WOULD WORK ON ALL ANIMALSTO KILL PEST
Food Grade DE is safe, can be fed to chickens for parasites.
But you need to warn your readers that Pool Grade DE is a known carcinogen, can cause lung cancer.
Tomato Hook Worms! These are nasty critters and will destroy your tomato vines in a night. I use DE around the plant base and lightly dust the leaves. Cabbage Worms... Also, a major pest. For these pests, I dust around the plant base and slightly over the heads of leaves of the cabbages. But because these worms come from flying moth eggs, I also cage the bed with a covering of insect netting. Make sure your netting does NOT touch the cabbage leaves as the moths will lay eggs on top of the netting that is in contact with the leaves and when the eggs hatch, you will still get some worms through the netting. Not as many, but even a few will destroy your cabbage crop.
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?
