Understanding Diatomaceous Earth: A Natural Pest Control Solution

Diatomaceous earth (DE) has gained popularity as a natural and effective solution for pest control in gardens and homes. DE is derived from the fossilised remains of diatoms, microscopic aquatic organisms. It’s a chalk-like powder that can deter and eliminate a wide range of pests without the use of harmful chemicals. Below, we’ll discuss the intricacies of diatomaceous earth, explore its applications, discuss its effectiveness against different pests, address safety concerns, and provide tips on how to use it for optimal results.

What is Diatomaceous Earth?

Diatomaceous earth is a sedimentary rock that is composed of the fossilised remains of diatoms, which are ancient, single-celled algae. These diatoms have hard, silica-based shells, making them ideal for creating a natural insecticide. DE comes in various grades, but for gardening and pest control purposes, it is best to use food-grade DE, which is safe for humans, pets, and the environment.

How Does Diatomaceous Earth Work as a Pest Control Agent?

The unique structure of DE makes it an effective pest control agent and when pests come into contact with DE, the microscopic, sharp edges of the silica particles penetrate their exoskeletons, causing dehydration and eventual death. The abrasive nature of DE also damages the respiratory systems of insects, further contributing to their demise. This mechanism of action makes diatomaceous earth an excellent solution for controlling pests with exoskeletons. Those are mainly ants, beetles, fleas, cockroaches, and bed bugs. However, it is also effective at stopping slugs in their path.

The Effectiveness of Diatomaceous Earth Against Different Pests

Diatomaceous earth is a versatile pest control solution that can effectively target a wide range of insects. Here’s a breakdown of its effectiveness against common pests:

Aphids and Caterpillars

While diatomaceous earth may not directly kill aphids and caterpillars, it can act as a deterrent due to its abrasive nature. By creating a barrier of DE around plants, you can discourage these pests from infesting your garden.

Slugs and Snails

Slugs and snails dislike crawling over diatomaceous earth due to its sharp particles. Sprinkling DE around vulnerable plants or creating a ring of DE can help protect your garden from these slimy pests.

Fleas and Bed Bugs

Diatomaceous earth is highly effective against fleas and bed bugs. Its abrasive properties penetrate their exoskeletons, leading to dehydration and death. Apply DE around pet bedding or infested areas to eliminate these pesky parasites.

Ants and Roaches

Ants and roaches are no match for diatomaceous earth. By creating a barrier of DE around entry points and infested areas, you can deter these insects and prevent them from reaching your home or garden.

Other Insects

DE can also target mites, millipedes, earwigs, silverfish, crickets, and other insects with exoskeletons. Its ability to dehydrate and damage their protective layers makes it an effective natural pesticide.

Sap sucking Scale insect on a plum fruit tree branch closeup.

It is important to note that it is not effective against all pests. For instance, it may not be as effective against caterpillars with thick mucus layers or earthworms, which have adaptations that protect them from its abrasive effects.

Using Diatomaceous Earth Safely and Effectively

While diatomaceous earth is generally safe, it is crucial to take precautions to ensure its proper and safe use. Here are some guidelines for using DE effectively and without causing harm:

Choosing the Right Type of Diatomaceous Earth

When purchasing diatomaceous earth, opt for food-grade DE, as it is the safest option for use in gardens, homes, and around pets. Avoid using DE intended for pool filtration, as it may contain higher concentrations of silica and other impurities that can be harmful to humans and animals.

Applying Diatomaceous Earth

To use DE as a part of your pest control arsenal, follow these steps:

  1. Identify any Problem Areas: Find out where the insects are likely to infest or present themselves. Look for signs around entry points, crevices, or areas around plants.
  2. Create a Barrier: Sprinkle a thin, even layer of diatomaceous earth around the affected areas. Ensure that there are no gaps in the barrier that pests can easily pass through.
  3. Dusting Leaves (Optional): If pests are damaging the leaves of your plants, you can lightly dust them with diatomaceous earth. However, avoid applying DE directly to flowers to protect pollinators. Use an applicator for more accuracy and to keep your other tools free from the substance.
  4. Reapplication: Diatomaceous earth loses its effectiveness when wet, so it is important to reapply after rainfall or heavy dew. Regular reapplication ensures continuous pest control.

Safety Precautions

While diatomaceous earth is generally safe, it is important to take precautions to avoid inhaling the fine particles. When applying DE, wear a dust mask and eye protection to prevent irritation. Avoid creating airborne clouds of DE and keep it away from high-traffic areas to minimize the risk of inhalation.

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Additional Uses and Benefits of Diatomaceous Earth

DE offers several additional benefits beyond pest control. Here are some ways you can make the most of this natural substance:

Soil Improvement

DE can improve soil structure and drainage. Its porous nature allows it to absorb excess moisture, reducing waterlogging and promoting healthy root growth. Incorporate DE into your garden soil by mixing it in the top few inches or adding it to your compost pile.

Silica Source for Plants

DE is a valuable source of silica, an essential nutrient for plants. Silica contributes to stronger cell walls, improved drought resistance, and increased overall plant health and through using diatomaceous earth in your garden, your plants are going to benefit from the extra source of this mineral.

Livestock and Poultry Health

Diatomaceous earth is commonly added to livestock feed as a natural dewormer. It can help control internal parasites in animals, promoting their overall health and well-being. Additionally, DE can be used in poultry environments to combat mites and lice.

Environmentally Friendly

It is a natural pest control and it poses minimal risk to the local environment. It doesn’t cause harm to the soil, nor to any local water sources, birds, or other wildlife, and when used responsibly, DE can be a sustainable and eco-friendly pest control solution. One of the only drawbacks is that it is not as targeted as some biological pest controls.


Diatomaceous earth is a versatile and effective natural pest control solution. Derived from fossilised diatoms, it works by dehydrating and damaging the exoskeletons of insects, leading to their demise. DE can target a wide range of pests, but it is important to use it selectively and with caution to avoid harming beneficial insects and pollinators. By following proper application techniques and safety precautions, you can harness the power of diatomaceous earth to protect your garden and home from unwanted pests while promoting a safe and environmentally friendly environment.

Pest Problems Explained – RED SPIDER MITE

Red Spider Mite Description

Small yellow/olive mites which have dark patches on either side of the body, red spider mite are less than 1mm long. Also known as “two-spotted mite” they can be found in large numbers on the underside of leaves.

Super macro photo group of Red Spider Mite infestation on vegetable. Insect concept.

In bad infestations they can produce fine webs.

As day lengths reduce in the autumn, they become deep red in colour and leave the plants to overwinter.

Red Spider Mite Damage:

Red spider mites (Tetranychus urticae) and Cyclamen mite (Phytonemus pallidus) on damaged strawberry leaf.

The mites suck sap from cells on the underside of plant leaves, in the early stages, characteristic white speckles can be seen from the upper leaf surface.

As mite numbers increase these white speckles will increase in number, the leaf will take on a bleached appearance and die.

The mites are found in highest numbers on the underside of leaves although you may need a magnifying glass to see them!

As the population builds you will start to see webs and aggregations of mites at certain sites, usually the growing points of the plant.

Cucumber leaf affected by Red Spider Mites.

Red Spider Mite Life Cycle:

The mites go through 5 development stages. Egg to adult takes about 14 days at 21ºC, or less than a week at 30ºC.

Eggs are laid on the underside of leaves. Each adult female can produce more than 100 eggs in 3 weeks. They reproduce at alarming rates – 10 spider mite in May are capable of becoming 1,000 by June & 100,000 by July!

Red Spider Mite and eggs

High humidities can reduce the egg laying rate of the mites.

During the autumn, when day lengths shorten the mites turn deep red in colour and migrate from the plants to hibernate in crevices within the glasshouse structure.

Red spider mite can overwinter without feeding and re-emerge in the spring and summer to re-infest plants.

NB. Artificial lighting may stop the mites from hibernating.

Biological Control of Red Spider Mite

Red spider mite can be controlled biologically indoors or outside by using their natural enemy, the predatory mite Phytoseiulus persimilis which is unable to control any other mite species.

Red Spider Mite Pest Solution: Phytoseiulus persimilis

Phytoseiulus Description

Phytoseiulus (Pronounced: FY-TOE-SOO-LUS) persimilis is a predatory mite capable of eating large numbers of red spider mites, it moves amongst the plants to find its prey.

It is slightly larger than the red spider mite. With a pear shaped shiny red body, it has long legs and is a quick mover. Young stages are oval and very pale pink.

Phytoseiulus Life Cycle

Each Phytoseiulus can produce 50-60 eggs in 3 weeks. Egg to adult takes about 12 days at 20ºC (68ºF), and half that at 30ºC.

Many hundreds of spider mites will be eaten by a single Phytoseiulus during its life cycle, and it will eat all stages of red spider mite.

Red Spider Mite and eggs.

Phytoseiulus reproduces at twice the rate of red spider mite at 18ºC (64ºF) and above.

If all the red spider mites are eaten, Phytoseiulus will disperse and die.

Phytoseiulus Usage

  • Phytoseiulus must be introduced at the first sign of red spider mite infestation. If there is a history of this pest in a greenhouse or conservatory it is advisable to check carefully for signs of red spider mite activity early in the spring.
  • The air temperature must be around 20ºC (68ºF) for at least part of the day and humidity should be kept fairly high by damping down or misting. NB. The temperature must not fall below 10ºC (50ºF).
  • Phytoseiulus can be used indoors or outside provided the temperature is sufficient.
  • Phytoseiulus cannot be stored, it needs to be used immediately upon receipt.
  • As a basic rule you should achieve control of red spider mite in about three weeks if the starting ratio of red spider mite to Phytoseiulus is no greater than 20 spider mite to 1 Phytoseiulus.
  • You will know when Phytoseiulus is working as new foliage will not show signs of damage.
  • Like all Defenders biological controls, Phytoseiulus is harmless to children, pets and wildlife.

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