Diatomaceous Earth is a Superb Organic Insect Control for Darn Near Every Problem


Diatomaceous earth is one of the most effective of organic insect controls.

How's that for a great opening line?

So what is this stuff?


It is a geological deposit made up of the fossilized skeletons of marine and freshwater organisms (diatoms and algae). These skeletons are composed of hydrated amorphous silica and when crushed, they break up into microscopic bits. The interesting property is that these microscopic bits are razor sharp like so many bits of jagged glass.

But to humans and animals they feel like talcum powder


Right – how does it work?


Insects pick up the microscopic bits on the small hairs of their body. The jagged edges scratch at their bodies and pierce the protective waxy layers. They also eat some of it. The insects lose moisture and stop eating. They die. The powder also repels the "smarter" insects and they won't go near it.

Is it effective?


The USDA did some studies on it between 1963-1970 and found it was more effective than malathion in protecting grains.

How fast does it work?


It can take several days to kill a pest that has been exposed to this product. It is not a fast contact kill such as insecticidal soap.

Having said that, while soaps and other fast contact kill sprays have no residual action (you have to hit the insect to kill it) diatomaceous earth is a perfect long-term residual organic insecticide. As long it is in the area, it is effective and continues working and it is perfectly safe for skin contact to humans and pets.

Is it safe for humans and pets?


Yes, skin contact is no problem at all. It feels like talcum powder. The only caution is that you don't want to breathe the dust while applying it to the garden or house area.

Wearing of dust masks while applying diatomaceous earth is a recommended safe gardening practice.


You might read reports that diatomaceous earth causes silicosis. Pesticide quality material is usually over 97 per cent amorphous silica. Silicosis is caused by crystalline silica  and the diatomaceous earth or amorphous silica hasn't been associated with silicosis.   So while I recommend you wear a dust mask, I'd recommend you wear the same protection while in any dusty environment – from cleaning out the attic to spreading peat moss.

What insects does it control?


Darn near any insect will be killed by this product including the beneficials. This is why we don't spread it everywhere but are selective in how we apply it.

It will control all soft-bodied garden insects.

It will control earwigs quite nicely.

There are garden reports of it controlling slugs organically.

In houses diatomaceous earth is used to stop the entry of certain insects such as earwigs, ants, and cockroaches, and to control these and others (such as fleas) in food cupboards, carpets, basements, attics, pet bedding etc. You can put the powder in cracks and corners for better control.

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It can be used to treat the roots of new transplants and the barks of trees to stop chewing insects (it will not stop mice or rabbits but if these animals get it on their fur, they will not get fleas) :-)

External parasites on pets can be controlled by dusting the animal and the bedding area.

Internal parasites of large animals such as horses are also controlled by adding 2% of diatomaceous earth to the grain ration. There are unconfirmed reports that fly populations are reduced when diatomaceous earth is part of the feed formula.

You'll find that some newer formulations add insect lures to the product to further increase the effectiveness of the product. I have not used these and can't comment on them.



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