It’s that time of year when slugs and snails creep out of the woodwork (quite literally) and look for sources of food after their winter hibernation. My alliums are currently being ravaged and I’m out in the garden with a torch at 10pm on most evenings removing the hungry little beasts. Last year I conducted some tests to disprove the value of egg shells, pistachio nut shells, hair and chilli powder in preventing slugs and snails from eating our plants, all were easily crossed by snails. Young chopped brambles were a surprise snail barrier success though.

This year I’ve heard a lot about copper slug and snail barriers, copper alloy has some unique properties, it is naturally anti-microbial – it kills bacteria and viruses, from E. coli and flu to the super bug MRSA [1] (within a few hours of contact). Could this somehow be why copper works as a snail barrier? Well no… but here I explain more about snails and their relationship with copper. I have of course conducted a series of new time lapse snail vs. copper tape tests to see if it’s worth buying expensive copper tape…

Why should copper work as a slug and snail barrier anyway?

As members of the Mollusca group of animals, slugs and snails use Hemocyanin proteins in their blood to transport oxygen around their bodies (whereas we mammals use iron based Hemoglobin). These Hemocyanin proteins contain two copper atoms. This makes all molluscs very sensitive to the ingestion of additional quantities of copper. Too much copper and it prevents oxygen from moving around their bodies and they eventually die, unless they flee to safety.

Copper sulphate has been a common snail control method for a long time, it’s quite commonly used in aquatic situations where water snails have become a problem in the farming of fish[2] or growing rice[3]. There is no doubt therefore that copper alloy should make a slug or snail very nervous when confronted with a barrier of the shiny metal stuff.

Whilst many copper slug and snail barrier products claim ‘a small static shock will be delivered’ this is unproven nonsense that has been passed on from manufacturer to manufacturer as the best way to sell the copper tape’s benefits. Mildly electrocuting those pesky gastropods sounds nice doesn’t it after what they’ve done to your poor plants?! It’s good for sales but is probably NOT what is happening (there isn’t any evidence available and I have asked for it to no avail). Snail slime / mucous contains two acids: glycolic acid and hyaluronic acid – both of which have been used in skin care (for smooth skin and anti-aging) and the development of modern day products. In ancient Greek times snail mucous was used to treat wounds, burns and abscesses with some success [4]. I propose that the snail slime itself (with its acids) on contact with copper tape reacts with the copper alloy (IF… and that’s a big IF… it’s thick and contains enough copper alloy) to create a foul taste or suffocating effect similar to that of copper sulphate, hence the slug or snail gets a bad taste and then turns back to get a breather.

And then there’s ‘acid rain’

Copper sulphate is made by combining copper alloy with sulphuric acid. Whilst sulphur dioxide emissions from power stations have dropped enormously in Western Europe since the 1980s, there is still enough in the atmosphere for rain to contain traces of sulphuric acid. In certain places within the UK you will be receiving higher doses of sulphuric acid in your rain than others. What happens when this acid rain lands on copper alloy tape on your outdoor plant pots? It makes trace amounts of copper sulphate which runs down your pot and into the soil. I therefore put it to you that as the copper tape weathers, in some areas it releases traces of copper sulphate which makes it even more potent, especially on more porous terracotta pots that can hold onto the copper sulphate. If you live in a city there’s probably more chance of copper tape having this effect than if you live in the countryside. I can’t prove that it exists but it would seem logical.

Does copper tape stop slugs and snails? The Website Reviews

Looking at the product reviews on Amazon it seems that the usefulness of copper tape products sold to gardeners is a little more on the positive side than the negative – 60/40. I personally wonder whether or not the success disparity is caused by the minor geographic acid rain factor (as detailed above) or whether some batches of the copper tape are just badly manufactured or poorly tested before production (if tested at all):

Slug & Snail Barrier Price It Works (4/5 Stars) Defenders 4m £3.25 60% Green Blade 4m £2.39 61% Rentokil 4m £3.14 62% Doff 4m £4.30 70%

Copper tape DOESN’T work! (40%)

Copper tape DOES work! (60%)

My own copper tape vs snails – time-lapse tests!

TEST 1 DOFF Copper Slug Tape (2.3 cms wide) – SNAIL FAIL!



TEST 2 DOFF Copper Slug Tape (2.3 cms wide) – SNAIL FAIL!



TEST 3 VITAX Copper Slug Tape (2.3 cms wide) SNAIL FAIL!



TEST 4 GROWING SUCCESS Slug Barrier (2.8 cms wide) SNAIL FAIL!



Having decided that the copper tapes being sold in garden centres and the likes of Robert Dyas was just inferior and not suitable for the purpose for which they were purchased BUT given that people swear by copper tape I decided to look for a serious solution. I settled on electric guitar shielding tape from Six String Supplies Ltd for £7.45 (3 metres) and my word is this tape the business! It feels like copper alloy and is MUCH wider (5 cms) than the absolute rubbish being sold as a horticultural barrier:

TEST 1 Electric Guitar Shielding Tape (5 cms wide) SNAIL REPELLED!



TEST 2 Electric Guitar Shielding Tape (5 cms wide) SNAIL REPELLED!



In Conclusion

Copper DOES work as a slug and snail barrier if the percentage of copper alloy is high enough and the width is in excess of 4 cms. Don’t waste money on any of the other ‘gardening’ products tested above and be cautious of using anything else that comes in a similar sized box (or from a matching production line…).

As it happens most of my slug and snail problems are not pot related but allotment related. For that the boy and I have come up with a handy solution that will re-use plastic with electric guitar insulating tape AND provide protection to all of our allotment seedlings this year (in particular sunflowers, runner beans and squash):

RECYCLE PLASTIC AND MAKE YOUR OWN COPPER RINGS!

(A 7 year old camera man sorry about that…)

References