Diatomaceous Earth as an organic pesticide

 

Diatomaceous Earth, derived from the fossilized remains of Diatoms, is a deadly weapon against many garden pests. Unlike chemical pesticides, it poses no risk for kids, pets, wildlife or you.

 

It’s a beautiful spring morning. You go outside for your daily stroll around your garden and you stop short when you pass the hostas. Was someone using them for target practice last night? The foliage was beautiful yesterday and this morning it’s riddled with holes inside and at the edges. In less than twenty-four hours your hosta has gone from showcase quality to in-need-of-emergency-care

holes in hosta eaten by slugs and snails

Slugs and snails can create this damage in just one night

When plants develop damage like this seemingly overnight, the culprit is usually slugs or snails, which are also known to snip off tender shoots, including flowers and fruit. This damage creates stress on the plant and when the foliage is full of holes, a reduced ability to perform photosynthesis. The result is reduced growth and conditions favorable for other pests and diseases to attack the plant while it’s in this vulnerable state.

Slugs and snails crawl over your plants at night and cloudy days, chewing their way through your garden. When the sun is shining they hide where it’s cool and damp – usually at the base of the plant near the soil, or on the underside of large leaves. A dead giveaway of their presence is a “slime trail” – a track of mucous running down the leaves, usually on the underside.

In your panic, you might be inclined to grab a bottle of chemical pesticide and obliterate whatever it is that’s eating your plants, but that’s always a bad idea. Chemical pesticides may kill the target pest, but they’re also frequently toxic to birds, fish, and mammals-including you, your family, dogs and cats and other wildlife.

Getting rid of slugs and snails

For slugs and snails there are a number of well worn remedies which work quite well, such as removing leaf litter from your garden bed (depriving them of any cool, damp hiding place); hand picking; beer traps; and generally making your garden less hospitable to the critters. If those methods fail to reduce or eliminate the damage, then it’s time to use an organic pesticide and one of the most effective is Diatomaceous Earth. DE as it’s known, was used widely for about one hundred years before chemical pesticides were invented. Now that the dangers of chemical pesticides are well documented, DE is once again returning to use in agricultural and gardening circles.

Diatomaceous Earth is a 100% organic pesticide, derived from the fossilized remains of Diatoms, a type of hard-shelled algae. Diatoms are phytoplankton used as food by freshwater and marine animals. When they die, their skeletons settle to the ocean or lake floor and over time become thickly fossilized deposits. These are mined and milled and sold as various grades of DE for industrial and agricultural applications.

slug

This slug may be the culprit

What Pests does Diatomaceous Earth control?

According to the University of Arizona’s College of Agriculture And Life Sciences, DE is effective on any pest or insect with an exoskeleton, which includes those with six legs and arthropods with 8 or more legs. That definition includes slugs, snails, aphids, gnats, fleas, flea beetles, cockroaches, cabbage root flies, sawflies, coddling moths, twig borers, thrips, mites, scorpions, earwigs, silverfish, ants, bedbugs, pillbugs, ticks, etc.

How Diatomaceous Earth kills garden pests

Open a bag of DE and you’ll see a light, white powdery substance which looks and feels remarkably like talcum powder. To garden pests however, the tiny particles are razor sharp and will slice their exoskeleton when they climb across it. The lacerating of their shell exposes the creature’s inner soft tissue to air, effectively dehydrating the pest within a day or two. If that creature ingests any DE, it will shred their insides. DE is a real death sentence for them, but it’s absolutely safe for mammals, birds and fish. In fact, food grade DE (the grade you apply to the garden) is added to grain shipments to keep them free of pest infestation.

Diatomaceous Earth How To Use Diatomaceous Earth

As with any organic or chemical pesticide, Diatomaceous Earth should only be used when other control methods have failed-it’s the nuclear option. While DE is environmentally safe, it will kill anything with an exoskeleton, including the pests which feed on the target pest (remember, they’re not all bad). When using a broad spectrum pesticide you always run the risk of upsetting the balance of your garden’s ecosystem, so use it sparingly and with care.

Only use DE when dry weather is predicted for 72 hours, accompanied by low humidity. Diatomaceous Earth is about 80% silica, so when it comes in contact with high humidity or water, it absorbs a great deal of moisture, cakes up and loses its effectiveness. To apply, sprinkle it on the underside of affected leaves, around the base of the affected plants, and on the ground surrounding them. In a day or two, any further damage to your garden should noticeably cease.

Note: The Diatomaceous Earth that’s sold for use in pool filters is not the same grade as the DE sold as an organic pesticide. In fact, the filter-type is poisonous to you and your pets and won’t kill the insects. Only buy DE that is marked for use as a pesticide or food additive.

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About Todd Heft

Todd Heft is an organic gardener and freelance garden writer who lives in the Lehigh Valley, PA and has gardened for most of his life. When he isn't writing or reading about organic gardening, he's gardening. His first book, "Homegrown Tomatoes: The Step-By-Step Guide to Growing Delicious Organic Tomatoes In Your Garden" is available on Amazon now. Google
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5 Responses to Diatomaceous Earth as an organic pesticide

  1. Ron Hornung says:

    Earthworms…………………………………………………………………………………………………………………………………………………………..

    EARTHWORMS don”t love DE…it doesn’t suit their lifestyle

    • Todd Heft says:

      Ron:
      Yes, thanks for noting that DE will also kill earthworms, since they have a soft exterior. There’s no easy solution to ridding your garden of unwanted insects. That’s why I always stress that ANY insecticide, organic or synthetic, should only be used as a last resort. Any insecticide is a shotgun approach.

  2. James says:

    I have another organic pesticide recipe! :) Mix marigold leaves with chopped garlic bulbs, crushed chillies, a few spoons of baking powder, a tiny bit of wood ash and a small chunk of organic soap. Pop in a bucket, cover with water and leave for 4 days – then voila, you have pesticide!

  3. Todd Heft says:

    Adam:
    DE will take care of the majority of crawling and flying pests – a comprehensive list is in the article. I suppose one could always worry about other pests and insects, but that is futile. You should only ever use a pesticide against a specific pest and only when it appears. Using pesticides-whether organic or chemical-in a “preventative” capacity is a bad idea, as it invariably upsets your garden’s ecosystem. A gardener should only combat a pest problem that is present, not one that is potential. I use DE sparingly and only when the slugs or snails are truly damaging hostas or other plants. One has to accept a small amount of interference from the critters that share our garden. Typically they move on when weather changes or they get eaten by natural predators like rabbits, birds, and skunks. If we kill all insect life in our gardens, the gardens will cease to thrive.

  4. Adam says:

    I didn’t know there were natural pesticides likes this. That’s great to hear! However, you said that it is only effective against pests with an exoskeleton. Are there a number of insects that don’t have exosikeletons you still have to worry about? If so, are there any other natural solutions for them that we could try as well? In any event, this is a huge step for going green when you are creating a garden! Thanks Todd!

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