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. But Dr Hayley Jones, entomologist at the RHS and lead researcher, said: “With the likes of eggshells, barks and mulch so far proving no discernible deterrent to slugs and snails, we would recommend using proven formulas like nematode biological control if the damage is just too much to bear.”

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.

What can I do?

The RHS also plans to test alternative control methods, such as beer traps, and is currently working with BASF to investigate ways to combine scientifically proven control methods into pest management strategies. Help us do more research As existing lab studies have shown some of the barriers work, and as other experiments by Hayley hinted that copper tape could be effective, she’s not ruling the barriers out completely. She hopes to run the study again ona different slug population and different soil type at RHS Garden, Harlow Carr in 2019. 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!

According to the RHS, some slug species have clear benefits for gardeners, such as the leopard slug, which eats fungi and rotting material, helping recycle garden nutrients. Uniform Application of Copper Sulfate as a Potential Treatment for Controlling Snail Populations in Channel Catfish Production Ponds 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.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. 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.