Diatomaceous earth, also known as DE, is a naturally occurring sediment made up of fossilized remains of diatoms. Diatoms are a type of hard-shelled algae that lived in oceans, lakes and rivers millions of years ago. As these diatoms died, their skeletal remains accumulated on the bottoms of waterways and mixed with clay and other minerals. Over time, this mixture hardened into sedimentary rock loaded with the fossilized silica shells of diatoms.
These fossilized diatom shells give diatomaceous earth its many useful properties, including being an effective yet non-toxic pest control powder. The fine silica particles have very sharp edges that can cut and damage the waxy outer coating on insects and other arthropods, causing them to dry out and die. This is why diatomaceous earth is often used for controlling bed bugs, cockroaches, ants, fleas, ticks and other household pests.
Does diatomaceous earth lose effectiveness over time?
When properly stored, diatomaceous earth can maintain its potency and pest-killing properties for many years. However, there are some factors that can cause it to lose effectiveness more quickly:
- Moisture – DE loses its sharp, cutting edges when exposed to moisture. It’s important to keep it in air-tight containers in a dry location.
- Compaction – Compacted DE has less surface area exposed and is less effective. It should be kept loosely packed.
- Contamination – Exposure to dirt, dust or other particles can contaminate DE and reduce its cutting action.
- Age – Very old DE that has been stored for 10+ years may start to lose some potency.
- Sunlight – UV exposure over time can gradually degrade the fossilized diatom shells.
As long as you obtain fresh food-grade diatomaceous earth and store it properly in an air-tight container out of sunlight, it can remain effective at killing insects and arachnids for 2-5 years or possibly longer. Always buy DE from a reputable source and look for an expiration date on the packaging.
Tips for preserving diatomaceous earth potency
Here are some tips to help keep diatomaceous earth as potent as possible:
- Store in air-tight containers – This prevents moisture absorption.
- Keep containers in cool, dry place – Avoid excessive heat or humidity.
- Do not compact DE – It’s more effective when lightly packed.
- Use within 2 years – Replace old supply with fresh DE.
- Avoid cross-contaminating – Keep DE away from dirt, dust and clutter.
- Minimize UV exposure – Store containers out of direct sunlight.
- Buy food-grade DE – Ensure it’s fresh and high quality.
- Check expiration date – Use DE before the expiry date.
Be sure to read and follow all package directions to get the most out of your diatomaceous earth. Some products may have specific storage instructions to preserve potency.
How does diatomaceous earth work to kill pests?
Diatomaceous earth kills insects through mechanical action rather than chemical pesticides. Here’s how it works:
- Abrasive silica particles – Diatom shells have tiny sharp edges that can scratch and penetrate an insect’s waxy outer coating that protects them from water loss.
- Cuts in protective coating – The sharp DE particles scratch the waxy cuticle layer on the insect’s body, legs and joints.
- Insects dry out – Once their protective coatings are compromised, insects lose essential moisture and dehydrate.
- DE abrades mouth/body parts – Insects cannot eat or move effectively as DE scrapes mouthparts, joints and bodies.
- Death 2-4 days – Insects become completely desiccated and die within several days due to water loss.
Diatomaceous earth provides an effective mechanical insecticide that avoids the use of chemical poisons. As long as the microscopic diatoms remain sharp and angular, they can penetrate the waxy insect cuticle and cause death by dehydration.
Is heat-treated diatomaceous earth still effective?
Some types of diatomaceous earth are heat-treated or calcined to increase their silica content. However, this process can reduce the pest control effectiveness of DE by rounding the sharp edges of the diatom fossils. So calcined DE retains its ability to absorb liquids but loses some insecticidal properties.
For pest control applications, it’s better to use natural diatomaceous earth that has not undergone heat treatment. This preserves the razor-sharp silica shells that can cut through insect cuticles. Make sure the DE product you buy specifically states on the label that it is effective as an insecticide.
Does micronizing make diatomaceous earth stronger?
Micronizing is a mechanical process that grinds diatomaceous earth into a finer powder. By milling the DE into smaller particles, it increases the amount of surface area exposed. This can enhance the abrasive action and insect-killing power of diatomaceous earth in some circumstances.
However, micronized DE may lose effectiveness faster than granulated varieties. The finer texture also allows it to absorb moisture more readily. For continued insecticidal potency, stick with regular granular DE and keep it stored properly in air-tight containers. Micronized DE may provide an initial boost in performance but doesn’t have better longevity.
Can you test potency at home?
There are a few simple methods you can use at home to test whether your diatomaceous earth still has active insecticidal properties:
- Float test – Place a small amount of DE in a jar of water. Effective DE will sink and stay settled; expired DE may float on the surface.
- Rub test – Rub a tiny bit between your fingers. Sharper particles will feel gritty or abrasive.
- Scratch test – Use a fingernail to see if the DE can scratch into a soft surface like wood or wax.
- Color check – Fresh DE is usually bright white in color. Discoloration may indicate contamination.
- Clump check – DE that sticks together in clumps may have absorbed excess moisture and reduced efficacy.
While not definitive, these quick home tests can identify red flags like moisture absorption or lack of abrasiveness. To confirm potency, you’ll need to directly observe DE’s insect-killing effects.
How long does diatomaceous earth take to kill insects?
When insects crawl through diatomaceous earth, the microscopic fossil shells immediately begin abrading their protective outer coating. However, death will not occur instantly:
- 12-24 hours – Insects will begin losing bodily moisture and drying out as their waxy coatings are compromised.
- 24-48 hours – Incapacitation, lethargy and reduced ability to eat/move as dehydration worsens.
- 72+ hours – Complete death from desiccation once water loss exceeds critical levels.
While diatomaceous earth may not produce an immediate “knockdown effect” like chemical pesticides, it is highly effective at killing insects, mites and exoskeleton arthropods within 2-4 days of exposure.
Can you recharge diatomaceous earth that has absorbed moisture?
Unfortunately, there is no good way to recharge or restore the potency of diatomaceous earth once it has become exposed to significant moisture:
- Heating DE will not sharpen the edges again after they have dulled.
- Micronizing will grind DE into smaller ineffective particles.
- Chemical treatments do not regenerate worn fossilized shells.
- Saturation means moisture has likely reached deep into DE particles.
If your diatomaceous earth has absorbed excess moisture, it is best to discard and replace it with fresh DE. Always store unused DE in an air-tight container in a dry location to maintain its insect-killing action.
Does diatomaceous earth have unlimited shelf life?
While diatomaceous earth can maintain its potent pest-killing properties for many years when stored properly, its effectiveness does not last indefinitely. Some guidelines for DE shelf life include:
- 2-5 years – Typical shelf life for properly stored food-grade DE.
- 5-8 years – DE may start losing some potency after this time.
- 10+ years – Greatly reduced activity; time to replace supply.
- 20+ years – Virtually inert; fossilized shells are smooth & rounded.
For the best results, use diatomaceous earth within 2 years and replace any leftovers after 5 years. Write the purchase date on the container, check manufacturer expiration dates, and store DE in air-tight containers out of sunlight and moisture.
Conclusion
Diatomaceous earth provides an effective, natural pest control powder capable of killing insects, mites, roaches, fleas, bedbugs and other critters with an abrasive mechanical action. Its potency comes from fossilized diatom shells with microscopic sharp edges that scratch insect cuticles, causing lethal dehydration. With proper dry storage away from moisture, heat and sunlight, food-grade DE can maintain its powerful insecticidal properties for years. But over longer periods of time, the effects do gradually degrade. Always buy fresh DE from reputable sources, follow label directions, check manufacture dates, and replace supplies every 2-5 years for optimal performance.
