Slugs in the garden can be a huge problem and apparently copper is a good slug repellent. If you encircle your plants with copper tape, it will keep the slugs out. It must work – since there are a number of copper tape products on the market designed to get rid of slugs. But does this really work?
Why Does Copper Work?
There are two reasons given for copper working as a slug repellent; toxicity and electric shock.
Copper is a known poison for many organisms and some copper chemicals are used to disinfect and kill organisms. It seems to make sense that copper tape or copper wire would have the same effect. If you think about this for a minute you will realize this can’t work. Most homes in North America use copper pipe to deliver water in our homes. If it were toxic – would we be using them?
Copper compounds may be toxic, but copper metal is not.
The green patina developed on copper metal over time is a copper carbonate salt and could be toxic.
The second claim is that the slime from slugs connects with the metallic copper and the slug gets a small electrical shock from it. This is unpleasant and slugs stay off the copper.
I have not been able to find any scientific reference showing that this is true. It is just repeated thousands of times. So let’s apply some logic. You can create a simple battery by inserting copper wire and a galvanized nail into a lemon. This will produce a small current that is measurable. You need 3 important components to make this work; two electrodes of different metals, and an electrolyte–the juice in the lemon. If you want to see a lemon battery in action have a look at this video.
In the case of the snail we have the copper, and the electrolyte in the form of slug slime.The second electrode is missing. Also missing is the connection between the two electrodes which allows the current to flow. I don’t believe that putting slime onto copper will produce an electric charge.
Does Copper Repel Slugs?
Let’s look at some video evidence.
Source: Does Copper Work on Slugs? See and Decide for Yourself! Just for fun!
Copper pennies and wire do not seem to work. Most products on the market are a type of copper foil or copper tape so this might work better and in fact some people suggest that a wider strip is better than a narrow strip.
Source: Copper Tape vs Slugs
That seemed to work quite well. But what about this video?
Source: Garden Pest Update: Slug vs Copper
Maybe some slugs hate copper more than others.
And this one:
Source: Slugs vs Copper Tape
How to Get Rid of Slugs
Jeff Gillman, one of the Garden Professors, commented “When I’ve tested copper the slugs seemed to have a slight preference for not crossing it, but would if that was what they need to do to get where they were going. I’d call it a mild repellant” . I think this is a good summary. Slugs will not go out of their way to cross copper in tape form, but it is not a fool proof solution.
This myth is busted!
The Latest Science
The latest testing found that bread dough and bread dough slurry were the best attractant for various species of slugs and snails. It was more effective than beer.
Getting Rid of Slugs and Snails
There are all kinds of methods for getting rid of snails and I have reviewed several of these including:
- Eggshells Control Slugs – Do They Really Work?
- Getting Rid of Slugs With Coffee Grounds
- How To Get Rid of Slugs With Beer
- How to Get Rid of Slugs With Copper
- How to Get Rid of Slugs with Diatomaceous Earth
References:
1) Photo Source: Aspen Grove Gardens
Yeh well! What about a mearing of petroleum jelly all around he neck of hosta pots. This seems to work for me, but means you get messy when trying to move the pots around. What is the evidence?
I think some manage to helcopted in,anyway!
I am southern UK resident.
That might work – but is it really practicable?
so what DOES work to deter slugs please? 🙂
If you search the blog for slugs you will find a number of posts about this topic.
Beer works a bit, but most slugs just drink the beer and leave. Commercial bait works. Home remedies don’t.
1/2 -1/2 solution of vinegar and water. Put in spray bottle and hunt them down! If you have kids give them a bounty. Go out early in am or very close to dusk. It doesn’t hurt plants or soil,bout it melts slugs!
This is a bad idea – since other people spray with vinegar to damage weeds. It does hurt plants.
Hi there. People and inverts are different 😉 the copper pipe that gives us safe tap water will wipe out the invertebrates in my aquarium. Heavy metals are toxic for all of us in high enough doses, we have amuch higher tolerance than invertebrates. There are times I’ve had to use reverse osmosis water for my aquariums because of this. Copper treatments are used for fish because the copper kills invert parasites and doesn’t harm fish in lower doses, but it can wipe out reef tanks or desirable fresh water inverts, like snails.
Clearly you like Teh Science so here’s a data base of studies for inverts. http://www.pesticideinfo.org/List_AquireAcuteSum.jsp?Rec_Id
Don’t want to write a novel in your comment section, you get the idea. And it also makes sense, sort of, why someone thought copper tape would work and also why in reality why it wouldn’t. 🙂
Your link is not working.
Ugh. It doesn’t want to give me a usable link. It’s still easy enough to find. Go to home. Materials. Copper and it shows dangers of copper toxicity, then symptoms by genus. Dig deeper and you’ll find ld50 by species.
Have been trying out lots of ways of stopping slugs and snails and came to the same conclusion as yourself – copper tape on its own does not stop them. Tried coffee grounds, egg shells and other rough surfaces (have even tried inverted wire brushes – again does not work). The only thing (apart from pellets) that does work is two strips of copper with a voltage between them. Have developed a unit that can use existing copper tape and allows you to check if it is working with a battery life of 2 to 3 years. To date it has had 100% success on large pots and I am now going to try it on a raised vegetable patch.
craftyjay – I would LOVE to see an Instructable on your idea!
stick two copper tapes to the pot, in 2 rings about 1/2″ (1cm) apart. Get a 9V PP3 battery, and clip, the one with two wires and the clip (maplin sell them) and stand the battery behind the pot, with the wires connected, 1 to each ring. This will use no current so the battery will last 3-4 years, but will be enough voltage to stop slugs.
Here’s a video on this idea including test with slug. Works!
https://m.youtube.com/watch?v=ZoBeKS64_xc
Hi Robert! I just heard your interview on RootSimple blog and thought it was really informative and eye opening. I have a question about copper and salt but not in relation to slugs. My studio in my backyard uses ferric chloride liquid to etch copper plates (i’m a printmaker). I have heard that both salt and copper are very toxic to soil biology, so I would have never thought about disposing of it in the ground and normally keep it in a jug and wait until i can bring it to a proper disposal place. The amount of ferric chloride with dissolved copper bits in it amounts to maybe a half a cup a month (if that) that I usually dilute 4x and add baking soda to to neutralize it. Is it safe to drain into some kind of french drain into the ground? Is this a horrible idea? Thanks so much for your answers and thanks for your helpful blog!!
This is not really my area of expertise, but adding copper and sodium to soil is not a good idea. It would be better to collect it and dispose it with a recycling facility.
Regardless of the use of copper strips or electricity, some types of slugs have been know to drop down from overhanging trees or even lower themselves down a slime trail.
I suggest that people who say one or another methods works, should actually go out into the garden for several nights (wet and dry) to see how many slugs there are and how many get past the trap before claiming it works based on one test or saying that it ‘seems’ to have a effect.
I’m precarious about buying copper tape as it’s quite expensive and if it doesn’t work , I been using slug pellets and that I think is the best repellent , a line of salt around the base of pots can work also , and is a lot cheaper option. Good luck with it . 😀
Salt is a really bad idea. Sodium is toxic to plants.
Hi Robert, thanks for the post. You’ve saved me some money! Do you have any advice on what does work? Every year our hostas are decimated 🙁
The only thing I know that works is slug bait. The new versions are quite safe.
Encourage snakes and toads in the garden. make nice shelters for the latter.
Thanks for the feedback. I’ve never seen a snake around here in eight years (maybe they’re hiding), but toads yes. I’ll see what I can do to make them feel at home 🙂 Will slug bait harm the toads?
Probably. Amphibians are affected by most chemicals more than other life forms. But I don’t know if a toad would go and eat the bait. It will also depend on the type of bait. You can cover the bait and leave a small opening for the slug.
Hi find copper tape works where the plant is not close to a wall or other plants where slugs and snails can climb/drop/absail across etc. i have a wildlife garden with frogs,toads,sloworms and birds,so don’t use chemicals.In the UK we have pellets made from waste sheep fleece, i surruound young and slug prone plants with this and it forms a mat when wet which slugs and snails don’t like to cross, by the end of the season it breaks down into the soil but by then the plants have toughened up.
Ironically, so does putting beer into an aluminum pan to deter them away from plants… They love beer and if they land in it they drown. I tried this yesterday and attracted 7 slugs away from my plants.
“putting beer into an aluminum pan ” ” if they land in it they drown. I tried this yesterday ” ….and at a guess, I’d say you probably didn’t drown…It would however be a great way to go 🙂
I spread oatmeal and see no more damage after that (they eat it n blow up) you have to keep spreading it every few weeks or so but it works!
Do you have some scientific proof this works? Lots of talk about oatmeal blowing up insects – none of it true.
The copper works in the garden, so I suspect there is a reaction between the copper and the soil that can cause the copper to charge up to shock the slug. I would like to see a test like that with the wire in the soil around the garden bed.
There is no evidence copper works even with wires in the soil, but if you have a reference showing it does work, I’d like to see it.
Thank you for this info. I have recently tried putting segments of copper wire scattered round some plants. As yet it is too early to tell if it will have any affect. With reference to the theory of the electric currant being created you suggested that two different metals need to be present and this is correct. May I suggest that the natural iron in the soil would provide the anode for the production of a small electric current to occur. If my experiment proves non productive then I think that I might scatter some old nails around as well as the copper.