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
I have tried copper tape, eggshells, coffee grounds, and beer on my slug problem. Something drank my beer last night and must have eaten the trapped slugs as well, nothing in the trap, but my petunias were in tatters. Failure. This after having some success with beer. I seem to have had success with the tape. I surrounded the middle of two planters with copper tape and finally have petunias and pansies that aren’t nibbled to shreds.
Don’t want to kill slugs, just deter them. Someone suggested mint leaves-dry. He/she didn’t know if it worked when wet. I don’t believe in killing slugs–whenever man invades Nature by killing off it’s creatures, it creates an imbalance somewhere else (as we have SLOWLY learned). Man (and other people) are the worst environmental stewards.
Why don’t I see any DETERRENT METHODS?
Actually many of the DIY methods for controlling slugs are deterrent methods – like copper, eggshells, DE.
I use pallet collars as raised beds for my vegetable crops and slugs used to hike up the collars to get at the salad crops. I stapled two nickel plated copper wires 1/4″ (6mm) apart around the collars and placed polythene at the corners to insulate the wire conductors from the steel corner hinges. I attached battery clips to the wire ends and use the cheapest brand of PP3 battery.
It works, I have seen slime trails to the wires and then back down again but not past the wires. The wires draw no current until a slug causes conduction so the setup lasts the growing season and beyond.
I could take the setup to the nth degree by using a solar charged battery but frankly its less hassle for me just to use a cheap own brand 9V battery.
Shock treatment does work.
I have had a respectable amount of success in slug deterrence using copper mesh as a slug barrier on the outside of wood planters. The mesh is about 5″ wide, which is wider than any of the copper tapes I have seen for sale, and it’s easier to work with compared to the super delicate copper tape I tried, the tape I tried, and it’s easy enough to reuse (although not adhesive on it’s own)
If I go out at night I will usually see 2-3 slugs oozing circles around the bottom of the barrier but not crossing it. I have seen a slug or two successfully cross it, but it’s rare. If I had to guess I would say I get about 1/20th -1/200th the slug prevalence I used to previously high slug traffic areas I have since “protected”. (tough to say because I am too lazy to count, and I can’t tell how many slugs crossed the barrier vs just live on the other side)
I imagine barrier efficacy might depend on the width of the barrier and skinnier tapes might be less effective barriers than 5″ of mesh. I have yet to try using any other type of mesh (steel, aluminum) but if I get bored that might be a fun experiment. I also imagine in addition to whatever theoretical chemical/electrical property copper has that slugs don’t like, there is likely a mechanical component because irregular wire loops might be irritating to ooze across and there may be some variability in effect based on the size/configuration of the wire in the mesh.
My older planters have 6 month old copper mesh barriers and I have yet to notice any obvious decrease in effectiveness with oxidation/dirt, but if there down the road maybe I can mitigate it with a firm wire brush scrub.
The stuff I got off Amazon is about a buck a foot (and it’s a contiguous “tube” so you can cut it in half and still have a 5″ barrier at half that cost) but I bet there are cheaper ways of doing it. I am also experimenting with rolling the mesh loosely around the base of some of my younger fruit trees. I put a couple of revolutions of that crinkly tree wrap paper around the base of the trunk, then a layer of (not too tightly wound) copper mesh, and hold it on with some of that green gardening velcro so I can loosen and adjust with growth.
Regardless of exactly why it works, I would recommend copper mesh to anyone with a slug problem amenable to a physical barrier who isn’t too concerned about the aesthetics.
Thanks for making such a great site, I really respect what you are doing. As a neophyte gardener with a skeptical bent, the field is littered with misinformation and advertising. You are a breath of fresh air.
Copper definitely works according to the gardening experts.
http://www.gardenersworld.com/how-to/maintain-the-garden/how-to-deter-slugs-with-copper-tape/
Your so-called experts is a what we call a click bait site. They write any type of garbage to get readers to their pages so you click on links and they get paid.
Thanks for saving me the $50 or so I was about to spend! There’s so much info like this on the internet, that’s repeated thousands of times as you say, so MUST be true…except it’s not…
Very useful blog you’ve created!
Save money, I bought 3different types of sand. Didn’t work either. I’ve tried copper, I make jewelry and have lots of scrap in different gauges. None work. I have found DE works but if it gets wet ( watering plants) it doesn’t work so you must reapply! I will try slug bait but hopefully won’t attract snakes!
My friend suggested garlic water sprayed on the plants and left to dry. Apparently they don’t like the taste. Reapply every 2 weeks. Recipe below. Does this work?
https://www.bowdenhostas.com/pages/Garlic-Wash-Recipe.html
No idea – but probably not. If it did, it would be used more.
I’ve tested solid copper rings which I made from some spare copper roofing strip. Did it work? Yes and No; the difference is oxidation.
I put a clean shiny copper ring on the ground and filled it with a dozen or more slugs and snails. It worked; try as they might none of them could escape. Even when climbing over each other to form a mound the height of the ring. The snails on top would stretch out to touch the edge of ring and withdraw immediately. It looked liked they were reacting so some unpleasant stimulus. When I used a dulled oxidized ring they all climbed out is short order.
Because I have the rings already I use them and they work well but only for a couple of days, until they oxidise. However that is long enough for my beans etc to get going up the poles and out grow the slugs. When I want to use them again I remove the oxide by dropping the rings in a bucket of water with a tea spoon of citric acid.
Your ‘deductions’ about ‘electric current’ appear somewhat limited. Having worked in roofing for a few years I know not to combine certain metals together because they can corrode as a result of contact in the presence of water unless they are electrically compatible.
I am not a chemist but guess it is due to some kind of ion exchange or electron donation. My guess is that something similar is taking place between the bright copper and the molluscs. Roofing metals are chosen for the job because their oxides adhere to their surface and are chemically inert under normal atmospheric condition. Knowledge of this fact is what lead me to triy the experiment in the first place.
I wouldn’t waste my money on copper tap because my experiment shows it could only have a very temporary effect if any. I’m not sure I would buy the rings ether if hadn’t had the spare metal. Copper scrip is expensive, I haven’t purchased any more even though I know it works under the right conditions. Perhaps I’m waiting to see how long my current 24 rings last given the need for repeated soaks in citric acid.
Certain metals, when they touch do undergo a chemical reaction. But I don’t think they produce a conducting current.
You may be correct. As I said I am not a chemist. Although I’m not sure that ‘Conducting current’ is the same as ‘exchanging an electrical charge’. But who really cares. The issue is whether or not it works and if so, under what conditions.
My criticism of your comments on ‘Electrical current’ as it related to the use of copper is that it represented a deductive approach not an empirical one. Things often fail or succeed for reasons other than we anticipate. There is no substitute for testing.
The problem, as your blog highlights, is that different tests gave different results. In one video the copper was wet and in another it was dry as you and others pointed out. But in addition the wet copper was shiny and the dry copper was dull; surface oxidation. Some of the test used copper foil, I used much thicker copper strip (0.6mm). I don’t know all the variables at work here. I was only pointed out my experience in order to help others make a choice. As I’m sure you were.
I’ve worked out that fashioning the copper rings myself from a 10m roll of 50mm x 0.6mm thick copper strip (£51) would cost out at about £1.50 each (33 rings). I already have the basic tools which would otherwise cost around £40.
I’ve only used my rings about 6 times (twice per growing season). So far they show no real sign of deterioration so I’m definitely thinking about buying a 1/2 roll of copper just to make rings out of. I’m still a little concerned they might get stolen from the allotment. If I get beyond 10 uses I will probably bite the bullet.
I have successfully kept slugs out of my planter by setting the planter inside a tray of salt. A situational solution, but it’s worked for me.
Slugs are a huge problem in my garden. I was able to write a whole blog post about the damage they’ve done to my seedlings (). I don’t know what method I should try next. What do you suggest?
Commercial slug bait.
I removed your link since it was not working. Feel free to try posting it again.