Diatomaceous Earth

By Daniel Fuller

If you’re looking for a broad-spectrum insecticide that is residual but non-toxic, you might want to give diatomaceous earth (or D.E. for short) a go. It’s a white powdery substance made of the fossilised remains of aquatic crustaceans called diatoms.

When dry, the tiny particles are extremely sharp and are able to pierce an insect’s exoskeleton, and its desiccant properties mean that it draws moisture out of their bodies which is why it’s so effective at killing insects.

 

Diatomaceous earth. Image/ SprocketRocket, CC0, via Wikimedia Commons.


Sprinkle some D.E. powder on the leaves to kill leaf-sucking and chewing insects, and it will be effective as long as it’s dry. When it’s wet, it becomes completely ineffective at cutting or absorbing moisture. Another method of application is to spray the leaves with some powder dissolved in water; after the water evaporates, the leaves are left with a coating of the dried powder.

Once you’re ready to stop the effects of D.E., you can simply spray the leaves down with a hose while being mindful of where the residue ends up. Obviously, anywhere that the powder dries out will be a harmful surface for insects.

Although silica is abundant on earth, it’s rarely in a form that plants can absorb. It’s a non-essential nutrient for plants that can provide a range of benefits, including increased photosynthesis, longer roots, and increased yield. It can also help plants defend against biotic pests and diseases as well as abiotic stressors such as drought.

D.E. is a valuable source of plant-available silica that can be applied wet to the leaves and the roots with the aid of a watering can.

 

 

People with chickens will often use the powder in bedding because it keeps mites and insects away. It’s also been known to be used on mattresses that are infected with bed bugs, and the scalps of people suffering from head lice.

It’s a great natural non-selective pesticide that will kill most insects indiscriminately, so be warned that it will kill pollinating and predatory beneficial insects that come into contact with it as well.

It doesn’t harm worms and snails due to their slimy coating, although they don’t seem to like crawling over the dry powder.

The same properties that work against insects work on a much smaller scale in human and animal lungs. D.E. is not as damaging to our lungs as other hazardous materials, but just try to avoid breathing it in as much as possible.

Its absorbent and porous qualities mean that it can be used in potting mixtures, but keep in mind that as long as it’s wet it won’t be effective as a pesticide. Biogenic amorophous silica is another silica-based soil additive that is actually marketed to use as to amend soils or to include as part of a potting mix.

Although food-grade D.E. is non-toxic, keep in mind that plants need to photosynthesise so coating their leaves isn’t necessarily going to be a great long-term solution.

D.E. isn’t a magic bullet. It’s just another tool in your Integrated Pest Management (IPM) toolbox that you can use when you need to knock a pest population on the head. You’ll still need to employ other genetic, cultural, physical, and biological control methods as well.

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