If you are looking for a different way to manage crawling insects around the garden, home or outdoor areas, diatomaceous earth is an interesting option because it works very differently from conventional chemical insecticides.
Rather than poisoning susceptible insects, diatomaceous earth acts primarily through physical contact with the insect's outer protective layer. When appropriately applied in dry areas where crawling insects are likely to travel, the fine particles can damage and disrupt this protective layer, contributing to moisture loss and dehydration.
Soil Solutions supplies Perma-Guard Food Grade Diatomaceous Earth / Fossil Shell Flour for a range of household and garden applications.
However, successful diatomaceous earth insect control depends heavily on where, how and under what conditions it is applied. It isn't an instant solution, and spreading large amounts indiscriminately around the garden isn't necessarily more effective.
Understanding how it works can help you use it more selectively.
Diatomaceous earth, often abbreviated to DE, is a naturally occurring material formed from the fossilised remains of microscopic aquatic organisms known as diatoms.
Over long periods, the silica-rich remains of these organisms accumulated into deposits that can be mined, processed and milled into the fine powder we recognise as diatomaceous earth.
Different deposits and processing methods produce different types and grades of DE, which is why products shouldn't automatically be considered interchangeable.
Soil Solutions supplies Perma-Guard Fossil Shell Flour, a natural freshwater diatomaceous earth product that can be used effectively as an insect killer.
Unlike many conventional insect-control products, DE doesn't depend primarily on a chemical insecticide to affect susceptible crawling insects.
Its action is predominantly physical.
How Does Diatomaceous Earth Affect Crawling Insects in the Garden?
To understand how DE works, as a pest control, it helps to look at the outside of an insect.
Many insects have an external skeleton, or exoskeleton, that provides structure and protection. Associated with this outer surface are waxy lipids that help reduce moisture loss.
When a susceptible crawling insect moves through appropriately applied dry diatomaceous earth, microscopic particles can adhere to its body.
These particles can disrupt and abrade the protective surface and absorb lipids associated with the insect's outer layer.
As that protection is compromised, the insect can lose moisture more readily.
The result is desiccation — excessive drying or dehydration.
This is an important distinction because DE isn't working in the same way as a conventional contact poison.
Pest Control: Physical Action vs. Chemical Insecticides
Many conventional insecticides rely on an active chemical ingredient that interferes with an insect's nervous system or another biological process.
Diatomaceous earth uses a fundamentally different mechanism.
Its effectiveness depends heavily on physical contact between susceptible insects and the dry powder.
That creates both advantages and limitations.
An insect generally needs to encounter the treated area for DE to have an effect. If insects are nesting or travelling somewhere the powder cannot reach, simply having DE elsewhere in the garden isn't going to solve the problem.
It is therefore better to think of DE as a targeted pest control-management tool rather than something that should simply be spread everywhere.
What Crawling Insects Can Diatomaceous Earth Affect?
Diatomaceous earth is generally associated with managing susceptible crawling insects and other arthropods that physically contact the powder.
Depending on the situation and product directions, potential targets can include insects and bugs such as:
- ants
- cockroaches
- fleas
- silverfish
- some beetles and weevils
- certain crawling garden pests
Effectiveness varies considerably according to the species, lifecycle stage, environmental conditions, and how the DE is applied.
Slugs are affected by diatomaceous earth (DE) primarily through tactile irritation and mechanical deterrence, rather than being instantly killed by it.
Some infestations will require several control methods rather than relying on DE alone.
Direct Contact Is Important
One of the most important principles of diatomaceous earth insect control is simple:
The insect needs to encounter the DE.
For example, if ants are travelling along a clearly identifiable route, placing a thin layer of DE across or alongside that route is more logical than covering an entire garden bed.
Likewise, if crawling insects are entering a shed through a particular gap or moving behind pots along a wall, those areas can be more useful treatment locations.
This targeted approach can improve the likelihood of contact while reducing unnecessary distribution of powder.
We'll explore this particular pest in greater detail in our upcoming guide, How to Use Diatomaceous Earth for Ants.
A Light Application Is Usually Better Than Piles of Powder
More isn't necessarily better with diatomaceous earth.
Large piles or thick barriers can sometimes simply encourage insects to travel around the treated area rather than through it.
A light, even application across an insect's likely travel route can provide a better opportunity for contact.
Potential treatment locations could include:
- cracks and crevices
- insect entry points
- along known crawling routes
- around suitable garden structures
- beneath or around pots
- selected dry areas where crawling insects are active.
Application should always be appropriate for the particular environment and consistent with the product directions.
For more detailed garden application information, see our guide to How to Use Diatomaceous Earth in the Garden.
Why Dry Soil Conditions Matter
Moisture is one of the most important limitations when using DE outdoors.
Diatomaceous earth performs best for this purpose while it is dry and loose enough to contact the insect effectively.
Rain, irrigation, heavy dew and other sources of moisture can wet the powder, reducing its effectiveness as a dry insect-control material.
This makes timing particularly important in Australian gardens.
If rain is forecast shortly after application, it may be better to wait for a suitable dry period. Areas regularly hit by sprinklers may also require a different approach.
After heavy rain or watering, the treatment area should be checked once it has dried. Reapplication may be required where the original powder has washed away, clumped or been dispersed.
This is one reason DE shouldn't be treated as a one-application solution.
What About Pots and Container Plants?
Pots and containers can provide useful opportunities for targeted application because insect activity is often easier to identify.
Crawling insects may travel:
- around the base of pots
- along shelving
- between containers
- through cracks beneath pots
- along nearby walls or structures.
Rather than covering the entire area, identifying these routes allows DE to be placed more strategically.
Moisture still matters. Regular watering can quickly wet DE placed in exposed locations.
This becomes particularly important with pests associated with moist potting mixes. For example, our upcoming guide How to Use Diatomaceous Earth for Fungus Gnats in Plants will look at why moisture management is just as important as the DE itself.
Will Diatomaceous Earth Work Immediately?
Diatomaceous earth shouldn't be treated as an instant knockdown insecticide.
Because its action depends on physical contact and subsequent moisture loss, results can take time and vary according to the insect and environmental conditions.
You also need to consider the source of the infestation.
DE might affect insects travelling through a treated area without eliminating insects, eggs or colonies located somewhere inaccessible.
Ants are a good example. Treating workers travelling along a trail may reduce activity, but this does not necessarily mean DE has reached or eliminated an inaccessible nest.
Persistent or substantial infestations may require additional control measures.
What About Beneficial Insects?
This is where responsible use becomes particularly important.
Diatomaceous earth's physical action isn't intelligent or selective. It doesn't distinguish between an insect you consider a pest and another insect you want in the garden.
Susceptible beneficial insects may potentially be affected if they come into direct contact with the powder.
For this reason, DE should not be spread indiscriminately over flowers, foliage and areas actively visited by pollinators.
Avoid applying it directly where bees, butterflies and other beneficial insects are feeding or likely to make contact with the powder.
Targeting known pest routes and problem areas is a much better approach than broadcasting DE throughout the garden.
Does Diatomaceous Earth Affect Earthworms?
Unlike insects, earthworms have soft, moist bodies rather than the waxy exoskeleton that makes many crawling insects susceptible to the drying action of DE. Research has found that appropriate applications of diatomaceous earth can have no significant adverse effect on earthworm survival.
Use Diatomaceous Earth as Part of Integrated Pest Management
Diatomaceous earth can be most useful when it forms part of a broader integrated pest management (IPM) strategy.
IPM means understanding why a pest is present and combining appropriate methods rather than automatically relying on one product.
Depending on the pest, this might include:
Identifying the pest correctly.
Before treating anything, determine what you're actually dealing with.
Removing food sources.
For household pests, spilled food, pet food and organic debris can encourage ongoing activity.
Managing moisture.
Some insects thrive in damp environments. Addressing leaks, excessive watering or persistently moist potting mixes can help reduce favourable conditions.
Closing entry points.
Sealing cracks and gaps may reduce insects entering sheds, garages and buildings.
Using physical controls.
Traps, barriers and manual removal can sometimes complement DE.
Applying DE selectively.
Place it where susceptible crawling insects are likely to contact it rather than treating unnecessarily large areas.
This approach recognises an important reality: no single pest-control method is appropriate for every situation.
Common Mistakes When Using Diatomaceous Earth for Insects
Several mistakes can reduce the effectiveness of DE.
Applying too much
Thick piles aren't necessarily more effective. A light application across an insect's travel route is generally more useful than creating large mounds.
Applying it just before rain
Outdoor applications can lose effectiveness when the powder becomes wet or is washed away.
Treating the whole garden
Broad application increases unnecessary exposure of non-target organisms and wastes product.
Expecting immediate results
DE isn't an instant knockdown treatment. Physical contact and subsequent dehydration take time.
Ignoring the source of the infestation
If insects are breeding somewhere inaccessible, treating the visible individuals alone may not resolve the underlying problem.
Assuming “natural” means risk-free
Diatomaceous earth is a fine mineral dust. Avoid breathing airborne dust and follow the product label and handling instructions.
Targeted Application Is the Key
The biggest takeaway isn't simply that diatomaceous earth can affect crawling insects.
It's how you use it.
DE works through physical contact, so successful application involves identifying where susceptible pests are travelling and placing a light layer in appropriate dry locations where contact is likely.
That is generally more sensible than spreading large quantities across an entire garden.
Weather, moisture, insect behaviour and the location of the infestation all influence results. DE can therefore be a useful component of pest management, but it shouldn't be presented as a guaranteed solution for every insect problem.
Used selectively and as part of a broader pest-management strategy, it provides Australian gardeners and householders with another practical option for managing certain crawling insects.
Frequently Asked Questions
Does diatomaceous earth kill insects instantly?
No. Diatomaceous earth doesn't generally act as an instant knockdown insecticide. Its physical action damages or disrupts the insect's protective outer surface, contributing to moisture loss and dehydration. The time required varies according to the insect, exposure and environmental conditions.
Does diatomaceous earth need to be dry to work against insects?
Dry conditions are important. Moisture can substantially reduce DE's effectiveness for this purpose. Outdoor applications may need to be checked and reapplied after rain, irrigation or other conditions that wash away or wet the powder.
Can I spread diatomaceous earth over my entire garden?
Targeted application is preferable. Apply DE only where appropriate and where pest activity has been identified. Avoid indiscriminate application, particularly around flowers and areas where bees, butterflies and other beneficial insects are actively feeding.
How much diatomaceous earth should I use for crawling insects?
More isn't necessarily better. A light, even application across appropriate pest routes or treatment areas is generally preferable to large piles of powder. Always follow the directions provided with the product.
Can diatomaceous earth be used as the only form of pest control?
That depends on the pest and the severity of the problem. DE can be useful as one component of an integrated pest-management approach, but persistent infestations may require sanitation, moisture control, exclusion, traps or other appropriate pest-control methods.
Looking for Food-Grade Diatomaceous Earth?
Soil Solutions supplies Perma-Guard Food Grade Diatomaceous Earth (Fossil Shell Flour) for Australian customers.
View Perma-Guard Diatomaceous Earth at Soil Solutions
Sources and References
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National Pesticide Information Center – Diatomaceous Earth Fact Sheet
This would be my primary reference for the article. National Pesticide Information Center
Diatomaceous Earth Fact Sheet – NPIC -
National Pesticide Information Center – Diatomaceous Earth
A shorter reference explaining DE's abrasive action on an insect's exoskeleton and its use against pests including fleas, cockroaches and beetles. The page was updated in 2023. National Pesticide Information Center
Diatomaceous Earth – NPIC -
NPIC – Is Food Grade Diatomaceous Earth Okay for Pest Control?
This is particularly useful for the safety section. Importantly, NPIC points out that “food grade” does not automatically mean a product has been evaluated or labelled for pest-control use, and it recommends minimising dust exposure. This page was updated in July 2025. National Pesticide Information Center
Food Grade Diatomaceous Earth and Pest Control – NPIC