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I have an organic garden, and use diatomaceous earth to discourage slugs from eating my plants. Lately I have worried that the diatomaceous earth might hurt the earthworms in my soil. Does diatomaceous earth have any detrimental effect on earthworms?

Cary Jensen
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It appears that earthworms will not be harmed by it. "Diatomaceous Earth will not harm warm-blooded animals or earthworms Earthworm farmers use it to treat their worm beds for parasites, fungus gnat larva etc. Earth worms are structurally different from insects in that they can actually digest particles of DE. The particles are then eliminated in their castings."

http://www.ghorganics.com/DiatomaceousEarth.html

Klendathu

Klendathu
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I'd add that the diatomaceous earth must be food grade for use in areas where there are worms - I couldn't find out why, except that pool grade diatomaceous earth will kill them.

Bamboo
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    Crystalline silica in the pool kind, which comes from salt water sources, is probably harder to digest than the amorphous silica in food grade diatomaceous earth, which comes from fresh water sources. I could be wrong about that being the reason. You can change amorphous silica into crystalline silica by heating it enough. Also, the pool kind is cancerous to humans, while the food grade kind is GRAS (generally regarded as safe). I imagine worms can get cancer. – Brōtsyorfuzthrāx Apr 02 '15 at 02:15
  • I seriously doubt that pool grade DE is cancerous. I had pool for 15 years, and it had a DE filter. You add the DE to the filter by pouring into the skimmer, in other words, right into the water stream. I don't think that DE would be used in pool filters if it was cancerous. The only mentions that I've seen suggesting that pool grade DE is cancerous have been from people selling food grade DE. – Cary Jensen Apr 11 '15 at 22:45
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DE harms insects because it gets between pieces of their carapace and cuts them up and dries them out.

Worms are not insects and although a pile of dry DE might be rather excruciating to them, it won't harm them in the soil.

Escoce
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DE, or Diatomaceous Earth, is made up of diatoms. Microscopic water critters. There are salt water and fresh water diatoms. It is not poisonous. Therefore critters will walk right through it as if it were dirt. That’s how it kills them as mentioned above the razor sharp edges of these really tiny diatoms work their way into insect critters. I have used it numerous times over the years. in the past I have recommended it to kill bedbugs which it does for the same reason it kills any other bugs. And bed bugs are very suspicious of anything that might even closely resemble poison. Therefore do not use pool grade diatomaceous earth because it contains other chemicals in it. it is not pure diatomaceous earth. Beer is strained through fresh water diatomaceous earth. Bakery items contain it as a leavening agent. You would never do anything like that with pool grade diatomaceous earth. The worst thing that I can find and have found over the years is the dust it creates when you put it down. I use a small sifter, put it down close to the floor around the edges of your room. That’s where most insects run. Think thin dust it’s not a pile. Wear a mask to scatter. Breathing in LARGE amounts of dust can cause silicosis; think factory workers. Outdoors use a pillow case filed with DE tie it closed and drag it around the yard. It will kill out a lot of walking insects. Oh yeah. I dust the dogs and cats with it.

C W Carlile
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