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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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35 Comments

  • Tess

    If it kills Moths does that mean it kills Butterflies? And what about Caterpillars? I have milkweed in my garden to feed the endangered Monarch Butterfly Caterpillers. It is so satisfying seeing the Monarch Butterflies soon after.

    I use DE on my cats and was reading here about the use in the garden. But I need to know if it is harmful to caterpillars especially, since they are often on the plants and on the ground around the plants…and hurting them would further endanger Monarch Butterflies!! 🦋🦋🦋🦋🦋

    • Aaron (Mr. DeannaCat)

      Hi Tess, DE mainly affects creatures with a hard exoskeleton such as ants, roaches, beetles, etc. so I wouldn’t be too worried about it harming the caterpillars. Is there a reason why you would use DE around your milkweed plants? DE is typically something we use in specific and targeted areas, what issue did you have where you were going to use DE?

  • Sam

    Aaron, thanks for this info. It seems that you recommend a much smaller concentration of DE in water than what I’ve seen elsewhere. In fact, I use a heaping cupfull per gallon water. After spraying on vegetables, it dries to a very noticeable white coating. Is your lower concentration effective enough and I’m wasting it?

    In addition, DE does not stick very well to plants. But kaolin clay sticks a bit better, so I experimented with mixing both DE and kaolin clay (commercial product: Surround WP) with water, using vigorous shaking, and it sprays very well. Again, I put a good cupful of both ingredients in a gallon of water. My question however is, do you know if the clay will interfere with the insectcide properties of DE? I’m wondering if the tiny clay particles could clog up the intricate microscopic structures of the DE. Any thoughts?

    Thanks also for the micropicture of the DE.

    • Aaron (Mr. DeannaCat)

      That’s good to hear that you can use a larger amount of DE per gallon of water, we are usually worried about it clogging the sprayer although we don’t usually have to treat our garden with this method. If you find that mixing DE with clay helps create a better spray, I wouldn’t worry too much about them interfering with each other’s pest control properties. Hope that helps and good luck!

    • Sandra

      I sleep in basement and around this time I have crickets visiting up until late October. Can I use this in my basement, yes it would be close to my sleeping quartets

      • Aaron (Mr. DeannaCat)

        Hi Sandra, yes DE will work on crickets as the DE will get into their exoskeleton which will lead to their death. You would want to create a barrier around your living quarters so the crickets would have have to cross the DE to get into your basement. However, if they choose to jump over the DE, it won’t have much of an effect on them. When using DE, you want to make sure to keep the dust of the DE to a minimum because it is not something you want to breathe as it can be harmful if done so. I believe some people may also use glue traps placed around areas of entry. Hope that helps and good luck!

    • Aaron (Mr. DeannaCat)

      Sprinkling the DE around your yard or mixing it with water and spraying throughout your property can help once the DE has a chance to dry out. However, we have yet to treat any animals with DE aside from adding it to our chicken coop floor so I can’t comment on how to use it on you dog. Good luck!

  • Mary

    Hello,
    I’ve been using DE in a spray bottle to control Lace Bugs on Rhodies and Azaleas, or try to anyway. But I am running into a problem I haven’t seen addressed anywhere yet. The DE clogs the sprayer and ruins it. ESPECIALLY at the 1/2 cup DE per 2 cups water level. (Yes, I shake it constantly.) I was able to keep my sprayer working for a couple of seasons at a much lower DE concentration, but even that ruined the sprayer. This last attempt, I got about 1/5 of a small rhodie sprayed before it clogged and completely stopped working. What to do??? I want to use DE so badly for pest control and need to spray UNDER the leaves….

    Thank you for a great article and I appreciate any advice!
    Mary

    • Aaron (Mr. DeannaCat)

      Hello Tracy, that could possibly work but DE is rendered somewhat useless when it is wet which makes it difficult to use with seedlings. Keeping your soil blocks from becoming overly wet will help out in keeping the gnat population down although that can be difficult to do. Hang some of these sticky traps to cut down on the amount of gnats flying around your space. Good luck!

  • Susan C]

    I purchased DE at Home Depot, but it did not say good grade. Is it safe to use in the vegetable garden>?

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