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.
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?
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!
Other popular methods for getting rid of slugs include coffee grounds, and beer. For more information on these methods have a look at:
1) Photo Source: Aspen Grove Gardens