How to Use Diatomaceous Earth for Organic Pest Control in the Garden

Last Updated on October 31, 2021 by Phil

Want to learn how to use diatomaceous earth for organic pest control in the garden? This guide will show you what kind of DE to use and how to properly use it to eradicate insects and bugs while staying safe.

Table of Contents

What is Diatomaceous Earth?

Diatomaceous earth, also known as DE, is a fine white powder that comes in packages you’ll find in garden centers. It is made from fossilized remains of water plants and algae called diatoms. These plants have been present in the Earth since prehistoric times.

DE is found in sedimentary rock. It is then mined and ground into powder form making it look very similar to baby powder.

To the touch, it feels soft and smooth. But, when placed under a microscope you’ll see at it has sharp and jagged edges which makes it effective as an insecticide.

This makes diatomaceous earth useful in the garden to get rid of pests. However, that’s not its only use. As such, you’ll see many different kinds of DE, some of which are used for swimming pool filters, industrial products, food, cosmetics and even pharmaceuticals.

In the garden, it is very important to only select “Food Grade” Diatomaceous Earth. This is the type that is safe for plants and humans.

If you buy other kinds of Diatomaceous Earth, including filter grade DE (which is used for swimming pool filters), you will find that it contains high levels of crystalline silica which makes it toxic to humans.

That said, even when you’re applying food grade Diatomaceous Earth, you should use a dust mask to prevent inhaling too much DE dust. This can cause mouth and nose irritation.

Once the dust settles, it will be safe to remove the mask. Similarly, you don’t want to have your pests around until after the dust is gone.

How Does Diatomaceous Earth Work to Kill Insects & Pests?

As mentioned, Diatomaceous Earth feels soft and smooth when we touch it. But, if magnified many times over, you’ll notice that DE is actually composed of diatoms with very hard outer shells. These shells are made from silica which are among the hardest materials on earth.

And, to give you an idea, the earth’s crust is nearly 60% silica which makes it very sturdy, strong and robust.

Additionally, the silica in Diatomaceous Earth has sharp edges. Thus, any time bugs, insects and pests go through them, they end up experiencing hundreds of abrasions. When this happens, the damage of their outer waxy protective layer causes their bodies to lose moisture.

As a result, they end up dehydrating and dying withing hours to a few days depending on how much of their outer shell is compromised.

How Do You Use Diatomaceous Earth for Pest Control in the Garden?

In the garden, Diatomaceous Earth is primarily used as an insecticide.

It works in two ways.

By damaging the waxy layer, thereby injuring the pest and causing it to lose moisture.
By drawing out their internal fluid which eventually dries them out and kills them.

That said, how effective it is depends on a few factors. These include:

How big the infestation is
Type of insects you’re dealing with
Humidity
Temperature

One of the main advantages of Diatomaceous Earth is that insects do not develop a resistance or tolerance to it. This makes it a better option to many chemical insecticides which are somewhat like antibiotics in that the more you use it, the more tolerance the insects and bugs become over time.

Another benefit of DE is unlike commercial insecticides, it does not harm beneficial microorganisms and worms. This allows you to use it without harming the helpful creatures in your garden.

In contrast, off the shelf insecticides will annihilate all the insects without regard of whether they’re helpful or harmful to the plants in your garden.

However, it is worth noting that because DE is a powdery like substance, it becomes absorbent when wet. So, if you water your garden after applying or it rains, the effectiveness of Diatomaceous Earth can be significantly reduced depending on how much moisture there is.

How much you apply also affects effectivity. Light coatings are not as potent. And, you’re better off making lines of DE rather than just lightly dusting affected areas.

What Types of Pest Insects Does Diatomaceous Earth Kill?

Diatomaceous Earth is effective against many common pests including:

Thrips
Aphids,
Mites
Slugs
Snails
Ants
Cockroaches
Bed bugs
Earwigs

It is most effective with insects that have exoskeletons. And while it won’t kill them immediately, it will do so withing hours to a few days depending on the type of bug and how much damage it was able to cause.

The outer protective layer of these insects are easily damaged by the sharp edges of DE causing them to eventually dry out.

The important takeaway here is that DE is not a broad-spectrum pesticide. This means that it does not get rid of all kinds of bugs and insects.

It does not work against insects like cabbage worms and other caterpillars because these creatures have thicker mucus-like layers that let them move through the sharp edges of DE without any harm.

DE likewise does not work against fungi including powdery mildew. Similarly, it does not affect earthworms and bees.

Nevertheless Diatomaceous Earth is an effective yet inexpensive pest control and management tool you can use in the garden.

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

Yes and no.

For gardening purposes, it is very important to choose “food grade” Diatomaceous Earth. This is safe for both humans and animals.

In fact, food grade DE is used in commercial food products and beverages including filters for wine and storing beer.

Some people also say that DE helps improve their skin and nail. Although I cannot verify any of that because I’ve never tried it nor know anyone personally who’s attempted to try it. Thus, I cannot recommend it.

However, you want to still take precautions when applying as the dust can cause irritation to your eyes, nasal and mouth passages. When doing so, it is a good idea to keep your pets away and wear safety glasses and a dust mask at least until the airborne particles have settled.

On the other hand, non-food grade DE, including filter grade Diatomaceous Earth is toxic to humans and animals. That’s because it contains high levels of silica.

How to Apply Diatomaceous Earth

Like other pesticides, make sure to read the label and instructions carefully before using DE. Also, take the proper precautions as well.

The included directions will tell you how to properly use DE for getting rid of pests.

That said, there are two very effective ways of using diatomaceous earth to get rid of pests in the garden.

You can apply it by dusting it
You can create a spray then apply it that way

I’ll explain each of the methods below.

Dusting with Diatomaceous Earth (DE)

The simplest way to apply diatomaceous earth is to applying a dusting of it to the affected areas.

You can use a dust applicator to make things more convenient or you can just use a cup and carefully lay down the powder.

Make sure to wear a mask and protect your eyes as well while doing so. Also, keep the protective gear on until the dust has settled, or you have stepped away from the dusting area.

Before applying ensure that young kids, other people and pets are at least some distance away as well. Only allow them to come near the area after the dust has settled.

Ideally, you want to choose a day when there is no wind. The windier the way, the more troublesome the DE dust will be. Plus, strong winds will likely blow some of the application away.

When it comes to applying the diatomaceous earth in your garden, there are a few ways to do it.

Sprinkle it on the soil around the affected plants.
For potted plants, dust under the containers.
Apply directly on the plants. When doing so, make sure to cover both the top and bottom sides of the affected leaves with DE dust.

You can use a cup and a sifter to easily control how much you apply on the soil or the ground around the plants.

If applying on the plant itself, you’ll need to use your hands. Just make sure not to touch your face, eyes, nose or mouth until after you’ve thoroughly washed your hands.

Diatomaceous Earth (DE) and Moisture

Keep in mind that any kind of moisture will wash the DE away. So, if it rains, you’ll need to re-apply.

Similarly, you want to plan out when you’ll be dusting the diatomaceous earth so it is kept away from when you’ll be watering your plants.

That said, water helps the powdery substance stick. So, you can water before you apply. Other good times to apply is after there has been light rain or early in the morning when the leaves are still moist from dew.

Diatomaceous earth is most effective when the insects walk over it or the DE is directly applied on the pests.

Any time it gets wet, it becomes less effectively because like powdered concentrate juices, it gets diluted and many of the particles can get washed away.

So if you apply it on the ground, it is best that area stays dry for the next 3 to 5 days in order to give it time for the bugs to come across the DE.

Reapply the diatomaceous earth once a week until the pest problem goes away.

How to Create a Diatomaceous Earth Spray

If you want to avoid airborne DE dust, you can wet the diatomaceous earth then apply it as a spray. This reduces the risk of the dust flying all around.

I’ve also found that this is the best way to apply DE over a large surface. Although it will take longer to take effect since you need to wait for the water to evaporate and the DE to dry out.

While this is a safer way to avoid DE dust, I still recommend wearing protective gear even if you use this method for safety purposes.

To create your very own diatomaceous earth spray, mix:

1 cup of diatomaceous earth
½ gallon of water

Mix he two into a garden sprayer or spray bottle.

You can adjust the amount by scaling it up.

For example, if you want to use 1 gallon of water, use 2 cups of diatomaceous earth to make the mixture.

Make sure to mix the contents well and stir every so even since the DE tends to separate from water. This way you can make sure that the DE is well-mixed with the water upon application.

Since the solution is moist, you can apply it to different surfaces easily, including shrubs, trees and other objects. The sprayer makes it easy to do this.

Conclusion

Learning how to use diatomaceous earth as organic pest control in the garden is a cheap and effective way of getting rid of bothersome insects and bugs.

By following the steps above, you have a few options on how you can apply along with how to safely use DE in your garden.