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All Things Garden,  Pests

What is Diatomaceous Earth? How to Use DE for Garden Pest Control

Have you heard about diatomaceous earth, or perhaps a recommendation to “use DE!” to solve a pest issue, but aren’t quite sure what it’s all about? You aren’t alone! DE is an excellent organic material to use in the garden (or around your homestead in general) but is often misunderstood. 

Read along to learn all about DE and get answers to your frequently asked questions. This article will cover exactly what diatomaceous earth is, and how to use DE in your garden for organic pest control. We’ll explore what pest insects DE is effective against (or not), a few notes on safety and limitations, and how to apply it for the best results.

What is Diatomaceous Earth (DE)? 

Diatomaceous Earth, known as “DE” for short, is a very fine, chalk-like white powder. It is made up of the fossilized remains of single-celled aquatic microorganisms called diatoms. In a nutshell, it is ancient phytoplankton. Diatomaceous earth is found naturally in sedimentary rock and mined to use in industrial products, swimming pool filters, as an organic insecticide, in pharmaceuticals, cosmetics, and even in food.

Like its many uses, diatomaceous earth comes in many grades. We always choose to use food-grade DE for our garden and chicken coop, which is the most gentle and safe form. Filter or industrial-grade DE has a significantly higher concentration of silica and is considered toxic to mammals.

A hand is holding a small cup of diatomaceous earth outwards towards raised garden beds with pink zinnia, marigolds, and kale.

How Does Diatomaceous Earth (DE) Work to Kill Insects?

The diatoms that make up DE have tiny rock-hard shells. Those shells are made of silica, which happens to be one of the hardest substances on earth. Fun fact: the Earth’s crust is 59 percent silica, and the main constituent of more than 95 percent of all known rocks.

To us humans, diatomaceous earth feels silky smooth! However, when the powder comes in contact with certain target pest insects, the microscopically sharp edges of silica in DE creates hundreds of abrasions on them. The tiny glass-like shards deteriorates their body’s protective outer layer, making them desiccateor dry out, and die. 

An image of DE under a microscope, it resembles pieces of bone or plastic with various holes throughout it and somewhat jagged edges.
Diatomaceous earth under the microscope. Image courtesy of David Siodlak via Wikipedia

What Types of Pest Insects Does Diatomaceous Earth (DE) Kill?

Diatomaceous Earth is effective against any insect that has an exoskeleton. This includes fleas, mites, lice, ants, millipedes, earwigs, cockroaches, silverfish, bed bugs, crickets, centipedes, pill bugs, sow bugs, most beetles, fungus gnat larvae, and some grubs. While it doesn’t outright kill them, many snails and slugs do not like to crawl over DE (and it slows them down), so it can be used as a protective barrier or deterrent. We add a light dusting of DE under the wood shaving bedding in our chicken coop to prevent mites and lice. 

Diatomaceous earth is not effective against caterpillars such as cabbage worms. Because of their thick gooey mucus layer that helps them travel safely through gritty soil, DE does not harm earthworms either. That means you can safely use a light dusting of DE in a worm compost bin that has become infested with mites, fungus gnats, or ants. Diatomaceous earth is considered relatively safe for bees – when it is applied correctly, in moderation, and not in direct contact with them. 

A diagram showing pictures of various insects that DE can kill. It is labeled "Bugs DE Kills". Depicted are quite a few insects such as mites, spiders, aphids, pillbugs, ticks, fleas, and squash bugs to only name a few.
*Note that DE doesn’t kill slugs and snails, but it can help deter them. Image from Safer Brand.

Is DE Safe for Humans, or to Use Around Pets?

The good news is, DE is proven to be almost completely safe around humans, mammals, and wildlife! Chemically, DE is pure silicon dioxide (SiO2) and is non-toxic. In fact, diatomaceous earth is commonly used in the food and beverage industry for grain storage and beer or wine filters. It is often fed to dogs, cats, and other pets as a natural dewormer. I’ve even heard of people drinking DE to relieve constipation or improve the health of skin, hair and nails. (I don’t have any experience using it in those manners, so please do your own research there!)

The caveat here is inhalation exposure. It is not healthy for humans or animals to inhale fine diatomaceous earth dust. Long-term exposure is particularly dangerous, such as those working in the DE mining industry. Thus, heed caution when you’re applying DE to not create airborne clouds or breathe it in. To be on the safe side, you could choose to use a mask during applications, especially if you have respiratory issues. You also do not want to get it in your eyes.

How to Apply Diatomaceous Earth (DE) in the Garden

Dusting with DE

The easiest way to use diatomaceous earth in the garden is to simply sprinkle it on the surface of soil, around the base of plants, under potted plants, or other areas where pest insects are present. For example, we dust DE under and around the grow bags in our driveway garden that are prone to ant infestations. Or, in a ring around the base of plants that are being attacked by pill bugs. I typically dust it around with a small cup, scooping from the main bag. For a nice even application, use a flour sifter, garden duster, or fine mesh strainer.

You can also dust DE directly on infested plants themselves. However, that poses more risk to wandering bees. Bees are least present and active in the evening hours, so that is the best time for DE application. Avoid applying DE during windy conditions.

A garden bed is shown with a variety of vegetables from bok choy, to mustard greens, and tiny radish seedlings. The soil is chalky white after diatomaceous earth has been sprinkled over the surface of the soil.
See the nibble holes in the bok choy, and the tiny vulnerable radish sprouts? They were getting munched on by pill bugs – aka “rollie pollies”. A sprinkle of DE can help with that!

DE and Moisture

DE will harm any target insect that comes in contact with it, whether they’re directly dusted with it, or they walk over it later. That is…. as long as the DE is dry.

The main drawback with using diatomaceous earth is that when it gets wet, it’s rendered far less effective. Therefore, try to sprinkle it in areas that will remain dry for at least a few days, or plan to reapply it after watering or rain. In general, plan to reapply weekly as needed if the pest problem persists. When wet DE dries out once again, it may still work to kill insects – but it does have the tendency to clump. That is, unless it is wetted and evenly distributed in a spray form.

A birds eye view of three fabric grow bags with tiny potato seedlings sprouting up. Behind the bags is a scattering of food grade diatomaceous earth that resembles a white powder.
A dusting of DE around our potato grow bags in the driveway garden to stop the ants that otherwise invade! Learn more about growing potatoes in containers here.

How to Create a Diatomaceous Earth Spray

For a broad and even application of diatomaceous earth, consider making a wet DE spray. Mixing DE with water makes it easier to treat a larger surface area. For instance, to coat an entire shrub, large tree trunk, or pathways and structures. Again, the DE won’t be effective until the water evaporates and the DE dries out. Then, the surface will be left with a fine coating of DE powder.

  • Combine 4 to 6 tablespoons of DE per gallon of water.
  • Mix in a spray bottle or garden pump sprayer. Shake vigorously to thoroughly combine. 
  • Spray on leaves or the target surface until it is wetted but not heavily dripping off. Focus on the most pest-prone areas, including the underside of leaves.
  • The DE powder may try to separate from the water, so shake your sprayer occasionally during application.
  • Allow the solution to dry and begin to work.

When it comes to a widespread infestation of aphids, mealybugs, spider mites or other soft-bodied insects on a plant, we prefer to use a DIY soap insect spray over DE.

And that is the scoop on DE!

In all, diatomaceous earth can be a useful, simple product to control pests in an organic garden. We always have a bag on hand. Yet there are many other organic pest control methods that we rely on too, and more readily than we reach for the DE – including preventative measures, companion planting, manual removal, and more. Please keep in mind that an organic garden is never a “perfect” insect-free one! That simply isn’t natural.

Thanks for tuning in! Please feel free to ask questions, and check out these related articles:

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  • John Moorhouse

    I have a problem with Paralysis Ticks and Tick Nymphs in my garden. Can diamotaceous earth be used to control these pests?

    • Aaron (Mr. DeannaCat)

      Hello John, ticks have an exoskeleton with tiny pores that need to breathe. The DE will get into their exoskeleton and do its work. Good luck!

  • Thea

    Thanks for this!
    We’ve had a wet and hot summer season here on the NSW Central Coast of Australia and we’ve had a mite problem in our chicken coop. I composted they’re bedding without realising that the mite would linger and now we’re being bitten in the house!
    Was hoping to use DE in the compost bin and so glad to read the earthworms will be ok!

  • Sharon de Silva

    Thank you very much for your article, exactly what I was looking for. I want to bring something to your attention. It is much more likely that slugs or little green cabbage worms, made those holes in your plants, not pill pugs. Pillbugs eat decomposing matter and stay close to the ground. They are actually very beneficial to your garden. Gotta love, rollie pollies 🙂

    • Aaron (Mr. DeannaCat)

      Hello Sharon, pillbugs can absolutely be beneficial to the garden but there is a line where they can become a pest as well when there is an especially large population and you have tender young seedlings in the ground. We have witnessed them all over our plants, especially when heading out at night with a flashlight. Everything in moderation, in our other pest prevention articles we stress the idea of identifying what pest is in you garden before you go about treating it. Thanks for your input and happy gardening.

  • Kimi

    Can you mix DE in with horticultural oil? I plan to spray my plants with an oil/soap/cayenne mixture. Is there any reason not to include DE in the mixture? Does the oil & soap keep it too moist for the DE to be effective?

    I’ve had good luck with applying DE in water — after the water dries the DE does its job.

    • Aaron (Mr. DeannaCat)

      Hello Kimi, I am not sure how the oil and DE would mix or react together. Guess it’s worth a shot and let us know how it works out. Good luck!

  • Nancy

    Hi first off, I have to say I am in friggin love with your blog! I found it while trying to start up a raised planter bed and seems like any problem I encountered, your site had all the answers!! Fast forward a few months.. I’m in the process of amending the soil to increase aeration and also add more soil volume in general (compaction). As I was tilling, I noticed a few roaches scurrying away! Eek! Moving forward, I wanted to add DE, but I also wanted to add in some red wrigglers and nightcrawlers. What sequential order would you recommend or could I add both at the same time?

    • Aaron (Mr. DeannaCat)

      Hello Nancy, glad you’re finding the site useful and thanks for reading! In regards to adding worms and DE, I would add the worms first with the extra soil on top, then dust the top of the soil with DE for the roaches or beetles. DE is rendered useless once wet so adding it into the soil itself wouldn’t be beneficial. Hope that helps and good luck!

  • Oriana

    Your articles are always right on time: I was just talking to a friend about diatomaceous earth today! I’ve used it in the vegetable garden, but I didn’t know you shouldn’t put it on flowers. Is that only to protect the bees, or are there other concerns as well?

  • JG

    Let’s also remember our dear garden friends ladybugs, which are beetles. They eat so many pests in an organic garden. Thus DE is applied with much restraint around here, as DE does not differentiate between the good and “bad” beetles.

    • DeannaCat

      Definitely! That is one reason (of many) I don’t readily suggest using DE on plants themselves (and just on soil or concrete for ants, etc) if anything. At least in our garden, the ladybugs hang out on the plants. I don’t see them cruising on the soil much at all.

  • Anne

    Thanks for yet another great article – I really appreciate your content and lovely photos. I assume that when you are discussing bees you are thinking of honeybees, but many native bees and bumblebees (the most endangered) are ground-dwelling. Vital garden pollinators like squash bees find their forage in the garden too, so any flowers or blossoms should be carefully avoided to protect them.

    • DeannaCat

      Yes, thank you for that input – and communicating things I forgot to mention. I guess I would never dream of putting DE on/in flowers so I didn’t outright specify that! Thanks again for tuning in.

  • AnnieOcco

    Hi DeannaCat..

    I am a new subscriber, and I know that I will be enjoying your knowledge all the time!

    My question, and I am not expecting a miracle: Do you have any secrets/tops to stop Japanese Beetles before they decimate my garden flowers?

    Thank you.

    • DeannaCat

      Hi Annie – Thanks for being here! Well, I don’t personally have experience with Japanese beetles but I do know using beneficial nematodes on soil can kill them in their larval stage – before they even emerge as beetles from the soil. So, you could consider treating your soil in the fall and again in spring for that. You can read more about that in this article about beneficial nematodes and grubs. Once they’re out as beetles, I believe dilute neem oil spray can deter them from plants and also reduce their feeding/reproduction. I suggest to check out our article about properly mixing using neem oil. I hope that helps!

  • Ginger Dawn

    Thank you for this article. It’s so helpful and thorough, as is all of your information! I’m very grateful that you are taking the time to write out all of this. Have you considered writing a book? I love books, despite the internet popularity. I’ve been using DE for my garden and chickens for 3 years with great success though as you said, a vital garden isn’t perfect! While I am here I’ll mention that I really appreciated your information about aloe! I love that plant as an remedy for me and my family and I am excited to use her in the garden! Did you know that garlic, aloe, and onions were planted next to the pyramids when people were Building them? Very powerful plant allies indeed!

    • DeannaCat

      Hi Ginger! Thank you so much for the feedback, for tuning in, and for the words of encouragement! Yes, I have contemplated a book in the future but for now the blog gives me the ability to put out manageable chunks of work while I am still working full time outside the blog. I can’t fathom doing all three, or completely putting the blog aside to work on a book… so, maybe one day! Lol. Thanks again for being here. It means the world to me.

    • Bob Blanchard

      Hi. Bob here in the fl keys. Maybe youcan help me. Noseeums have infested my van. I live in the van. Tried neem spray, peppermint, on and on. Any suggestions as to how to get rid of them is truly appreciated. Thanx. Peace

      • Aaron (Mr. DeannaCat)

        Hi Bob, I’m sorry your living quarters are being infested by tiny insects. Have you tried hanging sticky traps, they may be your best option for decreasing their numbers. Good luck!

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