What is Diatomaceous Earth?

Diatomaceous Earth in the Garden

Diatomaceous Earth

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Gardeners are often given the advice to sprinkle diatomaceous earth (DE) around plants to deter pests. Not surprisingly, we’re asked, “What is Diatomaceous Earth?” We’ll explain …

What is DiaTOmaceous Earth? 

Diatomaceous earth (DE) is actually 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.

How Does DiaTOmaceous Earth Deter Garden Pests?

Snugs 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, and on those with hard shells too such as beetles, fleas, cockroaches, and even bed bugs. Since it is non-selective, it can harm good bugs as well as the bad guys. 

How to Use DE

Deep deposits of diatomaceous earth are mined in the western United States in places where lakes once covered the area millions of years ago. When shopping for it, look for “food grade.” The DE used in pool filters is not effective against garden pests.

Sprinkle bands of it around the plants you are trying to protect or for another level of pest control you can dust the leaves of a plant, for example, potatoes that are infested with potato beetle larvae.

DE works best when dry, even morning dew will lessen its effectiveness, so you will have to reapply after it rains.

Is DE Safe to Use?

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. Surprisingly, this product is not toxic if eaten! In fact we probably have been eating it for years unknowingly since it is often mixed with grain in storage to kill insects. It can also be found in toothpastes and skin care products. Some people take it a step farther and use it for treating internal parasites!

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 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 it use in crop production.

See the Almanac’s Pests and Diseases Library for more advice on solving gardening problems.

About This Blog

Get inspired by Robin Sweetser's backyard gardening tips. Robin has been a contributor to The Old Farmer's Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer's Market.

Reader Comments

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DE

Will it kill stink bugs? They have been terrible this year in my garden, and I am just thinking about how to have a better crop next year! Thanks!

Crushed Egg Shells

If you grind your eggshells up you save from your chickens you can make your own diatomaceous earth for free!!!! (:

DE

A few weeks ago when I was inspecting my cabbages (green & red), broccoli, and Brussel sprouts, I noticed the green cabbages in particular looked like swiss cheese. I quickly bought (non food grade) DE and sprinkled it with a sifter from the dollar store. It works. It stopped the damage almost instantly. I've since decided to use only food grade so the local cats don't get sick even though I have most of my plants surrounded with chicken wire. When my fall lettuce starts growing I'll use it on this to as this summer I was plagued with cinch bugs. I'm so happy I saw the article on DE from the old Farmer's Almanac. Thanks to all.

DE non food grade

More a question than a comment. Does non food grade do any good against insects and why would it lose it's usefulness by getting wet? Does it loose it's silica or would it return to it's natural form when it dries? I am in Texas so I want to use it in the house as well as the garden.

The non-food grade is not

The non-food grade is not recommended because it has been subjected to high heat which changes its silica into crystalline silica which can be harmful to humans and pets. That is why it is only used for filters. Food grade is called amorphous silica. Since DE works by cutting thru the exoskeleton of an insect and drying it from the inside out it is not going to be as effective when wet. After it has dried out it will be effective again. It is recommended to reapply if it gets washed away.

DE

Caution, wonderful product, but have heard it is harmful to bees, so research safe usage more.

It is recommended that you

It is recommended that you not sprinkle DE on the blossoms of your plants to prevent bees from coming in contact with it.

De

I have used de for years with no issues to the bees. All of my animals eat it from the fish to the horses, people included, it have loads of benefits the list ia just too long to post here!

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