Eggshells Control Slugs – Do They Really Work?

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Robert Pavlis

Eggshells control slugs, according to most books, and all kinds of gardening experts. Slugs and snails can be a real problem in the garden, eating all those precious plants. It seems to be a constant battle and eggshells are routinely recommended.

Do they really work?

Eggshells controlling slugs in garden
Eggshells trying to control slugs in the garden

Controlling Slugs

Many solutions have been proposed for controlling snails and slugs. I have already reviewed coffee grounds, beer, and copper. I’d now like to have a look at eggshells.

The theory is as follows. Broken eggshells have sharp edges, and if slugs crawl on them, they will get cuts on their bellies, and die. So they are smart enough to stay off the eggshells.

Testing Eggshells to Control Slugs

A website called Allaboutslugs.com has tested eggshells in a great little experiment. The following information and pictures are taken from their site, with permission. For full details on the experiment go to Eggshell Myth: good idea or all cracked up?

Microbe Science for Gardeners Book, by Robert Pavlis

Eggshells were crushed, and left outside for two weeks so that the rain could wash away anything that might attract slugs. Two pieces of lettuce were used as tasty bait, and one was surrounded with eggshells. Slugs were added.

Eggshells control slugs - start of the experiment
Eggshells control slugs – start of the experiment
Eggshells control slugs - 8 hours later
Eggshells control slugs – 8 hours later

Both pieces of lettuce were partially eaten, and slugs seemed to have no problem crawling over the eggshells. Even after 8 hours, the slugs were still having a good feast and did not seem to be suffering very much from all of the ‘cuts’ they got the night before.

Eggshells, Beer and Slugs

We know from How To Get Rid of Slugs With Beer, that slugs are attracted to beer – or at least yeast. Will they cross eggshells to get to beer? Here is a great video.

YouTube video

Do Eggshells Control Slugs?

The first experiment done by Allaboutslugs  (not reported here) had the slugs going to the eggshells first – they preferred them over the lettuce. Both of their experiments showed quite clearly that eggshells do not stop slugs.

The beer, slug and eggshell video shows the same thing. Slugs were crawling all over the eggshells and did not seem to mind.

Granted, this is just 2 experiments, with 2 0r 3 types of slugs. There are many types of slugs and snails and it is possible other types react differently to eggshells.

Building Natural Ponds book, by Robert Pavlis

Without further experimental evidence to the contrary, I have to conclude that eggshells do not keep slugs away from plants.

Does Egg Shell Size Matter?

One of my readers commented that the egg shell pieces in the above were quite large. A common suggestion is to break the shells into very small pieces. The theory here is that small pieces are sharper – or at least there would be more sharp edges. Would small pieces be harder for the slug to crawl over?

I could not find a good video with smaller pieces of egg shell, but I did find this video. I think it clearly shows that sharp objects don’t deter slugs or snails.

YouTube video

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

21 thoughts on “Eggshells Control Slugs – Do They Really Work?”

    • If you have a cat don’t use products in your garden that will harm your cat. If you are worried about your cat in other gardens – the cat should not be there.

      Reply
    • Your cat is probably part of the problem by destroying biodiversity, cats kill birds (amongst other things) and keep birds away, and birds would otherwise be eating slugs. so the presence of the cat in the first place is contributing to more slugs for everyone

      Reply
      • @Andy Lowe

        My birds just seem to search for worms in my no-dig beds and pull up or bury my seedlings in the process. I’ll try to imagine they were eating slugs in the process. Might make me feel better about it.

        Apparently slow-worms eat slugs too, but as I’ve seen slow worms hidden under mulches together with the slugs and obviously not eating them at that moment in time, I can only assume they have a limited appetite. Which is fair enough, I suppose.

        Reply
  1. We have heavy clay soil that favors the slug and snail. I have had no luck at all with iron based snailbaits. One thing that does work is wood ashes. Not only do they contain potash or K but apparently naturally occurring lye which kills slugs and snails. One has to source their ashes selectively and avoid treated wood, plywood etc and the packaged logs sold in grocery stores.
    I sprinkle around the most enticing plants like hosta and delphinium. Water washes it into soil like all baits but this actually adds K , the ‘quality’ nutrient. I am sure someone has an argument against this but it has worked well for me.

    Reply
  2. I have tried a coffee barrier with a slug. I actually sat down with the slug and watched it as it found the barrier. The used coffee grounds were dry and the slug was reluctant to pass over them. It was deterred to some extent and deflected its path to the area where the line of coffee was less wide.

    I tried salt too. The slug reached the salt, tried to arch over it, found the salt was too wide to do this and and made a tight 180° turn. I keep meaning to design a system that keeps the salt from washing away in rain while the salt itself prevents the slugs passing. Slugs really hate salt.

    Having used very dry egg shells ground in an old fashioned Spong mincer, my feeling is they probably work to some degree much in the way coffee does. However, I would use a thick and solid layer at least 2″ width, not the scattering as shown in the pictures above. In practice, I get through my year’s collection of egg shells within a week while protecting very few seedlings so egg shells really aren’t practical.

    I found this article interesting and it has made me think it would be useful to attempt a more scientific approach. My hypothesis would be that dry salt is an absolute barrier (assuming the slug cannot arch over it) and that the other materials, if dry, are a sufficient annoyance to the slugs that unless they are certain they want to cross the barrier, they will deflect their wanderings elsewhere. I suspect they probably prefer compact soil to anything dusty. I would also hypothesise that rain makes most barriers next to useless.

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  3. Snails consume eggshells to repair their own shells, so this makes as much sense as making a golden fence to keep away thieves. Source: I have a pet snail who is very clumsy.

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  4. Ducks seem to like slugs. Slugs would have taken over everything in nature if iron phosphate was the only solution (or egg shells, coffee, etc). It is probably why farmers over the years included ducks, along with the other farm animals.

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  5. Hi Robert,

    I’ve been using a mixture of coffee grounds and smashed eggshells, dried and well mixed, lightly sprinkled around my leafy greens for three or four seasons now. Over that time I’ve experimented by adding soil conditioner and a little lime as well.

    It seems to reduce pest damage by about 80-90% so long as I keep the garden and the plants well tended. I especially remove any leaves that droop and make contact with the grounds. I do prefer my silver beet leaves without those ugly holes! Of course, my mix doesn’t kill the pests, but it is safe for kids and pets.

    I hope this information helps your readers.

    Reply
    • Egg shells and coffee grounds are not keeping slugs away. You should not add lime unless your soil test indicates that you need it. Keeping the ground free of plant material may help in keeping slugs away – they actually prefer to eat dead vegetation and making it harder for them to find food may help. But it also keeps the beneficial insects away.

      Reply
      • Apparently iron phosphate, in the form it is sold (with added EDTA or EDDS), is quite toxic:

        “Enter a man-made chemical called EDTA, a chelating agent that causes the iron phosphate to release its elemental iron easily in the digestive systems of not only slugs and snails but of pretty much anything that eats it. EDTA or the similar EDDS are the only reason these baits are effective, yet interestingly the label only reads Active Ingredient: Iron Phosphate – 1%, Inert Ingredients – 99%. No mention is made of the presence of another chemical that can turn harmless iron phosphate into a deadly poison. Apparently EDTA was slipped through the cracks in our regulatory system as an “inert” ingredient, and inert ingredients do not have to be listed on the label. Since iron phosphate is harmless, and EDTA is the ingredient that makes it effective, not to mention dangerous, something is really wrong here.”

        This quote is from hostalibrary.org, googling is sure to lead you back to the article itself.

        Reply
        • You Are quite correct about the EDTA. I tried to find out how much EDTA is added to snail bait but did not find the answer. One comment said it was about 1%.

          EDTA is also a safe chemical. In fact if yo0u have metal poisoning, they feed you EDTA to absorb the metal.

          I agree it should be listed as an ingredient.

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          • If I understood correctly, the point was that iron phosphate pellets can be dangerous due to the fact that:

            1)they are indeed poisonous due to the added EDTA and
            2)they lack the bitter tasting compounds found in metaldehyde baits

            This would make them a danger to vertebrates, as they would not be able to ingest metaldehyde pellets due to the taste. Do you think this is true?

            Obviously, manufacturers could add bitter tasting repellants to iron phosphate pellets, but I guess that would mean they would be conceding there’s not much difference between I.P. and M.D. pellets.
            What are your thoughts on this?

          • Your statement “there’s not much difference between I.P. and M.D” is not logical. They are not the same thing chemically, and adding a bitter tasting compound to IP would not change that.

            EDTA has a oral rat LD50 of 2,000mg/kg, compared to metaldehyde at 283 mg/Kg – making it 10 times safer from a toxicity point of view. The quantity of EDTA in bait is very small, so I think we can consider the bait to be quite safe, even without the bitter additive.

  6. I use Oyster Shells ( that are fed to chickens to make their shells hard). I bought a bag from the farm supply store and put a generous (thick) amount around each Hosta. My Hostas looked fine up until I got hail storm in August and it ripped them to shreds. I am using this same method this year.

    Reply
    • I have only read about 1 experiment using oyster shells – and they did not work. If you think they work, please copy my experiment with slugs and coffee grounds, take some pictures, and let us know what you find.

      Reply
  7. Those experiments mirror mine over the last couple of years. I’m in mid-Michigan.

    I’ve tried eggshell barriers (useless) rough flooring sandpaper (useless) and copper tubing (useless) – all of these are often touted as highly effective mechanical barriers that slugs will not cross. Maybe in some places, but Michigan slugs slide right across all of it. I put continuous rings of each around my plants and saw no cessation of slug activity whatsoever.

    A bowl of beer kills them, yes. But it also attracts slugs that otherwise may not even have showed up in the first place. Also, useless.

    I do try to be as non-invasive and commercial-product free as possible but if those little buggers show up again this year to decimate my garden, sorry, I am using whatever Monsanto or Ortho or whoever has on sale to kill them right now!

    Reply
    • Iron phosphate works and is quite safe. both iron and phosphate can be used as nutrients by plants. Keep away from dogs.

      Reply
  8. Where on earth do all those shells come from? Eggs must be very popular over the pond.
    I actually do think that eggs are a superfood!
    I thought when I first saw it that your picture was a grave for slugs!

    Reply

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