I don’t like six-legged roommates. I used to spray bug killer, but it really stinks. And I’ve learned that the stink means it’s dangerous to me and my pets. Then I learned about diatomaceous earth.

I’ve got some little ants in my kitchen now, but the same stuff that got rid of the roaches will eventually work on them. And spiders, etc. What’s more, it can’t harm me or my pets.

Diatomaceous earth comes from the fossilized cell walls of aquatic microbes called diatoms. They have accumulated in the sediment of various bodies of water. These skeletons are made of silica, a substance that makes up 26% of the weight of the earth’s crust.

Diatomaceous earth doesn’t poison insects. They can’t develop immunity to it. Although it looks and feels like a smooth powder, it looks like shards of glass under a microscope. That’s because glass is also mostly silica.

When any insects get diatomaceous earth on them, they die. It gets stuck in the joints of their exoskeleton. It cuts body parts and the waxy protective layer. Moisture leaks out of the insects’ body, and they dry out. Unlike poisons, it kills insects by a mechanical process, not a chemical one.

Different kinds of diatomaceous earth

Silica, also known as silicon dioxide, exists in two natural forms, amorphous and crystalline. Most diatomaceous earth is made from amorphous silica.

When purified, it can be labeled “food grade.” It’s on the FDA’s “generally recognized as safe” list up to 2% added to food.  It is lethal to insects, but harmless to mammals, birds, and fish.

“Food grade” may seem like an odd term to use for a pesticide. It’s not like you’ll find diatomaceous earth as an ingredient in any of your cookbooks.

When farmers store grain, they mix it with lots of food-grade diatomaceous earth to keep insects from eating it. As a consequence, any time we eat grain, we eat a little diatomaceous earth. It doesn’t hurt us at all.

Some people deliberately take it internally to detoxify their bodies, among other uses. It’s probably safer than other detox methods.

Just be careful not to inhale a lot of it.

How to use diatomaceous earth as a pesticide

Be sure to use food grade diatomaceous earth—or something labeled as a pesticide––and not the kind for filtering swimming pools. Pool grade diatomaceous earth is up to 70% crystalline silica. It’s dangerous.

Only dry, powdery diatomaceous earth kills insects. Once it gets damp, it’s no longer the sharp, powdery menace. Also, it doesn’t act as a bait. It only works if it’s in the path of where insects go.

DiatomaceousEarth.com has more articles and suggestions than I care to try to summarize. Here are a few thoughts from there and elsewhere.

In the house

To kill cockroaches and other crawling insects in the house, apply it lightly under appliances and any other dark places they’re likely to hide.

If you know or suspect where bugs are getting into the house from outside, apply some there.

Dust it where you have seen bugs—or on them, if you get a chance. They must come in contact with it for it to kill them. They will see and avoid large clumps of diatomaceous earth. Use a duster or a flour sifter to make a thinner, less conspicuous layer.

Diatomaceous earth is about the only pesticide that works on bedbugs. Be patient. It will kill each adult bug in a couple of hours, but it doesn’t kill eggs. It can take weeks before all the bugs in the house have hatched and been exposed.

If you find fleas in the house, you can pour food-grade diatomaceous earth on rugs and carpets. With a broom, work it into the fibers. Be careful not to raise too much dust. Then let it sit for 12 hours or so and vacuum. Put it in your pets’ beds and anywhere else they like to lay around. It can dry their skin, so after a while, you’ll need to comb or brush it out.

I have read that you can mix some with water in a spray bottle to apply it to walls. The water will evaporate, leaving a dry layer of diatomaceous earth. I find it easier, however, to put some of it on my hand, shake it lightly to get a thin layer, and then blow it on the wall. You can turn away from the wall before you inhale again, just to be careful.

In the garden

Use food grade diatomaceous earth in the garden to protect fruits, vegetables, and flowers from parasites. You can reuse an old carpet cleaning container to sprinkle it on the plants most in need of protection.

You can also apply it to the ground to control slugs. Apply it late enough in the morning that the dew won’t moisten it. Reapply it after rain.

Unfortunately, diatomaceous earth will also kill bees and other beneficial insects. Apply it only where necessary. Keep it away from the flowering parts of plants that attract bees.

If you’re using diatomaceous earth during the time when bees are most active in your garden, you can try to cover the treated parts with a sheet. It will continue to work just as well on crawling insects. When the bad bugs are under control, stop using it and wash off whatever remains.

Risks of diatomaceous earth

Federal law has required registration of pesticides with the FDA since 1959. The first pesticides containing diatomaceous earth were registered almost immediately. There are now more than 150 products registered for use inside and outside of buildings.

Thousands more products with diatomaceous earth include skin care products, medicines, and clarifiers for wine and beer.

Food grade diatomaceous earth must contain no more than 2% crystalline silica. It is not specifically labeled as a pesticide. Officially, then, its risks and effectiveness have not been tested. Myriad users over several decades have tested it unofficially.

I recommend using it rather than labeled pesticides simply because it’s probably cheaper. And you can put it to other uses if you’re so inclined.

Any substance can cause harm in large enough amounts. Nothing in this world is without risk. Therefore, we need to know the risks and take necessary precautions.

Exposure to any kind of dust can cause respiratory problems. Inhaling small amounts of food grade diatomaceous earth can irritate nasal passages. Inhaling extremely large amounts can cause coughing and shortness of breath.

It also irritates the eyes, and long exposure can dry out skin. Therefore, you should be careful not to raise a lot of dust. If you do, wait for it to settle before you get too close to it. If food grade diatomaceous earth does enter the body, however, very little is absorbed. The lungs rapidly expel it.

Crystalline diatomaceous earth is another matter. Long-term inhalation can lead to chronic bronchitis, silicosis, and other respiratory conditions.

There are, however, almost no environmental risks to using food-grade diatomaceous earth. Silicon is the second-most abundant element in soil. When it gets into lakes or oceans, it’s only going back where it came from. Just remember the bees.

Sources:

Diatomaceous earth: effective natural pest control / Linsey Knerl, Gardener’s Path. June 8, 2017
Diatomaceous earth (food grade): bug killer you can eat! / Paul Wheaton, RichSoil
Diatomaceous earth general fact sheet / T.R. Bunch et al., National Pesticide Information Center, Oregon State University Extension Services. 2013
Is ‘food grade’ diatomaceous earth okay for pest control? / National Pesticide Information Center

Photo credits:
Diatomaceous earth. Source unknown
Diatomaceous earth under a microscope. Public domain from Wikimedia Commons
Roaches. Public domain from Wikimedia Commons
Bug on fruit. Some rights reserved by Line Sabroe
Ants on candy. Public domain from Wikimedia Commons ;