I have been told that Diatomaceous earth will help with the many slugs that enjoy the buffet that is my garden, since the micro-fossils irritate their slimy bodies. But will it help with other insects and caterpillars, especially gypsy moths? I purchased a bag that says "food grade" but I don't know if it is as effective as non-food grade DE. Any experience in this area would help. This is turning out to be an expensive organic garden this year!

  • Organic gardening in "choose 'organic' poisons mode" can be both stressful and expensive. AFAIK, DE is about useless on slugs (it works on hard-body insects by scraping their waxy layer and desiccating them) and is utterly non-selective as are most poisons, 'organic' or not. i.e. B.T. is "selective" to caterpillars, but kills all caterpillars, non-selectively. Hand-picking is gross, but effective for slugs, and you can also cheat by providing some nice boards to hide from the sun under, then pick them up and scrape the slugs into a container...
    – Ecnerwal
    Jun 2, 2016 at 14:30
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    @Ecnerwal- It does work on slugs, but it has to be dry to be effective. (Therein lies the rub. ) I also worry about it being non-selective, and only use it on my window moldings in my house, not in my garden. But, some people do apply it selectively in their gardens. diatomaceousearth.com/natural-slug-control
    – Diane
    Jun 2, 2016 at 14:51
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    ychirea1- This is not answering your question (so I didn't put it in my answer), but have you considered purchasing predator insects (like ladybugs), if your garden does not have a natural balance? I am lucky in that nature usually seems to do its job in my garden of balancing out good and bad bugs. (But luckily, I don't have a gypsy moth problem to deal with, either.) Here's a site that sells them, if you are interested in trying that approach. todayshomeowner.com/…
    – Diane
    Jun 2, 2016 at 15:32
  • No, the yard does not have a natural balance. Yes, I have a good crop of ladybugs. I seem to be working against time in this cycle, as the slugs and gypsy moths have already had a good run in this first planting.
    – ychirea1
    Jun 2, 2016 at 18:16
  • My understanding is that DE is not technically a poison, organic or not. It is as if you cut up an intruder by using shards of glass on the ground. Only it kills. Is that worse than drowning in beer? My question had more to do with the value of food-grade DE versus "pool" calcined DE.
    – ychirea1
    Jun 2, 2016 at 18:22

2 Answers 2


I do not use this in my gardens. I only use it sparingly, in certain areas, for serious infestations.

Slugs love beer. I pour a bit of beer in a shallow bowl, and they crawl in at night and drunkenly drown. (Recycled cat food or tuna tins work well, because you can just throw out the whole ugly mess.) If you don't drink beer, there are slug baits for sale. That being said...

Yes. Food grade Diatomaceous Earth will nonselectively kill all insects and caterpillars (both bad and good). But, it has to be dry in order to work. Even a slight dew will make it ineffective. It does not harm the earthworms under the soil when they eat it.

Do not use the pool grade stuff! It is only meant for use in swimming pool filters, has been linked to health risks and might kill your plants. (In fact, it's recommended that you avoid inhaling even the food grade kind, as it can cause respiratory distress in some people. I just avoid getting it in my eyes.) You are probably (harmlessly) eating some food grade Diatomaceous Earth every day, because grain and vegetables, etc., are stored in it, in the warehouses.

I put a small amount in a "puff" bottle so I can apply it very selectively, and keep the bag sealed against moisture. I bought a plastic bottle for $1 (the type use for ketchup or salad dressing) and that works really well. Some people use a shaker bottle for large areas.

While it supposedly is effective on gypsy moth caterpillars, unfortunately I have been unable to find any sites dealing directly with that ugly problem for advice.

This site is very informative about food grade Diatomaceous Earth. http://www.richsoil.com/diatomaceous-earth.jsp

This one discusses the pros and cons (like concerns about bees), and has suggestions on how to apply it to a garden. http://www.theprairiehomestead.com/2015/07/diatomaceous-earth-garden.html

This site discusses avoiding putting it on the flowers to try and protect the pollinators. http://homeguides.sfgate.com/diatomaceous-earth-garden-pests-84812.html

Used to control slugs https://www.diatomaceousearth.com/natural-slug-control/

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    ychirea1- I didn't see your reply until now. Although you can see all of our our responses on your post, we can't see yours unless you use the @ symbol in front of our names to tag us. (I am pretty new to the site, and this confused me, as well.) If you comment on my answer, it will show up. I agree about your question. It was pretty specific. I hope I answered it, okay. (But, you did not have to select it as the answer, and you can undo that.) Yikes, it can be annoying when people lecture about things that they are not a part of. Your question actually prompted me to pose one of my own ;)
    – Diane
    Jun 2, 2016 at 22:31
  • wonderful and thoroughly useful response, thank you!
    – ychirea1
    Jun 3, 2016 at 2:19

You are correct for the most part. DE or Diatomaceous Earth is in no way remotely poisonous. It’s water creatures. It is food grade because it is used in foods and to strain the smallest particles from beer. Water does not hurt just dry it out and crush it into powder. Remember it comes from water. On the other hand pool diatomaceous earth has chemicals in it. Smart bugs like bedbugs the smell those chemicals and avoid it. Food grade has no such chemicals in it and therefore months walk right through it as if it were dirt. Which it basically is. Having been crushed by other diatoms over the millennia. How people discovered all this stuff I don’t know but I’m glad they did.

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