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.

Diatomaceous Earth Products

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 – SOFT SCALE INSECT

Scale Insect (Soft Scale) Description

There are two distinct groups of scale insects – soft scale and hard scale.

The most commonly found soft scales are Coccus hesperidum – the adults are 3-5mm long, green to brown in colour, oval- shaped and appear slightly flattened, and Saisettia coffeae – the adults are 5mm or longer in length, deep brown in colour and dome-shaped.  Most soft scales have 6 legs and can move around the plant as they grow

Scale Insect (Soft Scale) Damage

The symptoms are similar to those of whitefly or aphids.

Soft scales are normally found congregating along leaf veins or stems. The scales feed on plant sap and produce large amounts of sticky honeydew.

Large populations will cause yellowing of the plant and defoliation. The honeydew results in the growth of black sooty moulds which ultimately kill the plant.

Soft Scale Life Cycle

Soft scales produce a number of eggs over several days. The eggs are laid under the cover of the adult “scales” which offer protection during development. The adult dies once it has laid its eggs.

Eggs hatch into “crawlers”, which are tiny legged creatures which disperse all over the plant and its foliage in search of a suitable site to settle down and become an immobile scale.

Scales grow relatively slowly and have a long life cycle. Saisettia coffeae takes about 95 days at 18ºC (64ºF) to complete it’s life cycle

Soft Scale Insect Pest Solution: Metaphycus

Metaphycus Description

Metaphycus (Pronounced: METTA-FY-CUSS) helvolus is a small parasitic wasp about 2mm in length. The female is yellow in colour and parasitises the young stages of soft scale when they have settled on the plant. It is quite active, walking quickly over the leaf surface. Metaphycus is pictured parasitising a scale.

Parasite Life Cycle

The adult female lays up to 6 eggs a day into soft scales. Before laying an egg, she tests the scale with her ovipositor (egg laying tube).  In so doing she kills up to four times as many scales.

The larva develops inside the scale and eventually kills it. These parasitised scales appear darker and flatter than normal. The parasite pupates inside the scale body and the adult emerges by cutting a circular hole in the dead scale. Adults can live for up to 2 months if enough food is available. From egg to adult takes about 11 days at 30°C and 30 days at 20°C.

Metaphycus Usage

  • Metaphycus is only suitable for use in a greenhouse or conservatory.
  • Metaphycus requires a minimum temperature of 22°C (72°F) for at least a few hours each day. This limits use to late spring and summer or hot greenhouses and conservatories.
  • Metaphycus requires good levels of light.
  • Metaphycus cannot be stored and needs to be used immediately upon receipt.
  • Metaphycus is harmless to children, pets and wildlife.