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 – MEALYBUGS

Mealybug Description

Mealybugs are small, soft-bodied insects which have sucking mouthparts. The females are oval in shape and can be up to 5mm long. They are white or whitish-pink in colour and are generally covered in a white waxy material. They have filaments made of wax around the edge of their bodies and tails.

The most common species found in glasshouses are the citrus mealybug which has very short tail filaments and a central grey stripe, the vine or glasshouse mealybug which has a pair of tail filaments about half the body length and no stripe (see right) and the long-tailed mealybug which has waxy tail filaments as long as the body and a grey stripe.

Mealybugs (Planococcus Citrus) on an orchid leaf.

The males, if produced by the species, are small and elongate in the young stage and develop into delicate winged insects.

Mealybug Damage

Mealybugs are often found in clusters on stems and leaf whorls. They produce honeydew which often leads to sooty mould growth.

Large colonies can weaken the plant because of the amount of sap being taken which can result in yellowing leaves & defoliation.

Mealybugs feeding from the stem of a plant

Root-feeding species are seen as white patches among the roots when re-potting, especially around the sides of the root ball.  Care is needed to distinguish them from root aphids

Mealybug Life Cycle:

Most mealybug species lay eggs. However, the long-tailed mealybug gives birth to live young, whilst the citrus & vine mealybug produce quantities of “waxy wool” in which they can lay up to 500 eggs.

Egg laying may take up to 10 days and reduces the size of the female mealybug considerably. The female dies once she has completed laying her eggs.

Once hatched the young, or “crawlers” as they are sometimes called, are very mobile. They disperse rapidly and find suitable sites in which to feed and settle. The females continue to feed until they are mature enough to lay eggs.

The complete life cycle takes approximately 50 days at 20ºC (68ºF), this is reduced to 25 days at 30ºC, higher temperatures may inhibit egg laying.

Biological Control of Mealybugs.

Mealybugs can be controlled biologically in greenhouses or conservatories by using their natural enemies Cryptolaemus or Parasitoids or a combination of both.

Mealybug Pest Solution: Cryptolaemus, Leptomastix and other parasitoids

Cryptolaemus Description

Cryptolaemus (Pronounced CRIP-TOE-LEE-MUS) is a black or dark brown ladybird with an orange head and tail, it is about 4mm in length and originally from Australia.

It’s larvae are white and look rather like very large mealybugs, up to 1cm in length, with a waxy covering, they are more mobile than mealybug.

Cryptolaemus Life Cycle

Egg to adult takes about 25 days at 30ºC or 72 days at 18ºC. Females start laying eggs about 5 days after emerging as adults, they lay single eggs into the woolly mealybug egg masses, and lay about 10 eggs a day, they can lay up to 500 eggs in their lifetime, they need a plentiful food supply to maintain egg production and females need to mate with males on a regular basis.

The larvae hatch out as voracious predators of mealybugs. Young larvae and adults prefer the smaller stages of mealybug, whereas the large larvae will eat mealybugs of any size. If mealybug is in short supply, Crytpolaemus may also eat young scale insects.

Cryptolaemus Usage

  • Being a predator, Cryptolaemus prefers quite high levels of mealybug.
  • Cryptolaemus is only suitable for use in a greenhouse or conservatory.
  • Cryptolaemus is a strong flier so if vents and doors are left open near to the treated plants they need to be netted over to prevent the Cryptolaemus from escaping.
  • Cryptolaemus should be released on the day of receipt, preferably in the cooler part of the day.
  • Cryptolaemus need the woolly egg masses of mealybugs in which to lay their eggs. Species that do not produce these may not be controlled. They will not control root mealybug.
  • Cryptolaemus work best in the summer and require a temperature of at least 20ºC (68ºF) for a few hours a day, and good levels of sunlight are required if they are to fly to new plants.
  • Cryptolaemus prefer landing on bushy, leafy plants and may be less effective on climbers and cacti.
  • Cryptolaemus is harmless to children, pets and wildlife.

Leptomastix Description

Leptomastix (Pronounced LEP-TOE-MASS-TICKS) are tiny yellow to black wasps, about 3mm long. They are parasites of the citrus and vine mealybug. Anagyrus, a similar parasitoid is also supplied with Leptomastix.  These target different stages of the mealybug lifecyle but like Leptomasix, only attack these species of Mealybug.

Leptomastix / Anagyrus Life Cycle 

Female adults lay their eggs in nearly  nearly or fully grown mealybugs. The parasitised mealybug becomes swollen and brown in colour, finally becoming “mummified”.

The emerging adult Anagyrus or  Leptomastix cuts a small circular hole in one end of the “mummy” from which they emerge.

The life cycle takes about 4 weeks at 20ºC (68ºF) and 2 weeks at 30ºC.

Leptomastix and Anagyrus Usage

  • Leptomastix and Anagyrus can be used in conjunction with Cryptolaemus.
  • They are only suitable for use in a greenhouse or conservatory.
  • Temperatures above 25ºC (77ºF) are required for some part of the day, along with good levels of sunlight.
  • Leptomastix and Angyrus are better at searching out isolated patches of mealybugs than Cryptolaemus.
  • They cannot be stored and should be used on the day of receipt.
  • They are harmless to children, pets and wildlife.

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