Using Diatomaceous Earth

by Catherine Haug

I have a problem with slugs in my garden.  I tried the cans of beer, but they attracted bees (including a mason bee) and flying ants, but no slugs. So I decided to try diatomaceous earth (DE).  This all-natural flour-textured substance has many uses around the home including:

  • causing slug, maggot, and insect death in the garden and landscape
  • solving an ant or bedbug problem in your home
  • getting rid of fleas on pets and livestock
  • worming of pets and livestock (and humans)

Diatomaceous earth is made from the silica-rich shells of diatoms. Most diatoms are found in the ocean, but food grade DE is made from freshwater diatoms, mistakenly called ‘algae.’  This is the same brown or golden algae that grows in fish tanks.

I learned from a piece on the local news recently that diatom algae grows on rocks at the bottom of the Clark Fork River in Missoula.  And I suspect it also grows on rocks at the bottom of the Swan and/or Flathead River, which means we would have a local source when we can no longer import it from a distant source.  All we’d have to do is figure out how to harvest and clean it. Does anyone have any ideas on this?

What is Diatomaceous Earth?

DE is a fine powder consisting of sharp, mineral-rich, microscopic shells of dead, fossilized diatoms, from the ocean or fresh water.  These sharp edges cut the soft tissue of many garden (and other) pests, causing them to dehydrate and die.  Thankfully, it doesn’t harm earthworms; nor does it harm the digestive tract of animals.

DE can be purchased in several grades:

  • Food Grade
  • Agriculture or Horticulture Grade
  • Pool Grade (not discussed in this article)

It can be applied as a dry powder, or as a slurry in water.

Safety Precautions:

You should use DE with care, because it can irritate your eyes, and lungs.  Therefore, it’s a good idea to wear safety glasses (to cover not only in front of your eyes, but also the top and sides), and a respirator or face mask designed for particulate matter (or dust).  Gloves are also recommended, so that you won’t later rub your eyes with DE on your fingers.

Once the DE dust has settled it won’t bother you.

For use in your yard and garden, you can use agricultural or horticultural grade DE.  Food grade DE can also be used. DO NOT use pool-grade DE, which has been heat-treated to form larger particles.


Jean H. recommends using an old sifter or wire mesh strainer to apply the DE powder in the yard, greenhouse and garden.

Another way to use DE is to make a slurry, a thin mixture of DE and water. A slurry will give more precise coverage, can be painted onto tree trunks for sunscald protection and to deter borers from laying eggs on the bark. (3)

In the Garden:

  • DE works against slugs and maggots, both in the soil and on top; it can even be dusted on leaves.
  • Use to control the following insects: ants, aphids, bedbugs, beetles, cabbage root flies, carrot root flies, earwigs, whiteflies, leafhoppers, loppers, mites, silverfish, and thrips.
  • Sprinkle it inside your greenhouse, or outdoors on fruits, vegetable plants, flowers, grains, and grass—up to and including the day of harvest.(1,2)

eHow has a good article on using DE in the garden. (2)

Jean H. recommends: when planting seeds, especially for root crops, sprinkle DE in the furrow so that it looks pretty white. Then add the seeds and cover.  Then, sprinkle some DE on top of the soil around them.

Around the House:

DE can be used to control the following insects, by sprinkling around the foundation of your home, and around infected areas inside your home:

  • ants, cockroaches, silverfish, bedbugs, fleas, box elder bugs, scorpions, crickets, ticks, and many other unwelcome pests. (1,2)
  • Can be used for  fleas, pillbugs, ticks and is helpful in dealing with fungus gnats. (1,2)

In the Home:

DE can be used in stored grain (to combat maggots): Add 7–10 lbs. of Food Grade Diatomaceous Earth to each ton of grain as it is conveyed into storage (That’s 0.8 ounces DE per 10 pounds of grain, for smaller quantities). (1)

For Pets & Livestock:

DE can also be used against ticks on pets.  In this case, choose only food grade DE, as your pets will lick the dust off their fur. While DE can irritate lungs, it won’t hurt the digestive tract.


Food grade DE can also be given to animals orally, for parasite control (photo, right, is from ESP Gathering: How to Keep a Family Goat).  Humans can use it this way as well. As an additional benefit, DE naturally contains over 14 trace minerals which improves health. (see Wolf Creek Ranch for instructions on this use.)

The following animals can be treated with DE for parasite control:

  • Humans
  • Dogs & Cats
  • Sheep
  • Goats
  • Hogs
  • Cows
  • Horses
  • Chickens and other poultry

Harvesting or collecting diatoms for DE

I’m still researching this topic, but i did find one book that includes information on collecting diatoms: Diatoms of North America, by William C. Vinyard, 1979.

Another source is Collecting And Identifying Diatoms – I by R. Fraser Bastow, F.R.M.S.



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