Using copper for slug control
Posted: Fri Feb 28, 2020 12:53 pm
Now that spring is approaching I'd just like to share the following about slug control that has worked for me even in a very wet part of the country. There's been a fair bit written about copper - that it's good or useless - but I have found that it's good for certain plants if you use it the right way.
I'm gardening in North Devon, where every exposed surface is covered in moss and lichen, and there seem to be a couple of slugs for every blade of grass on the lawn. I've been here for three seasons now, and in the first year, being used to the drier climate on the east side of the UK, I lost virtually everything, despite having 8 slug pubs on my very small veg plot. But over the last two seasons I've had good success in protecting most plants (except root crops) using copper foil rings on cardboard tubes, which I've put around the bases of the young plants when they get planted out.
I use the cardboard tubes out of the centres of loo roll or kitchen paper - the loo roll ones are just about the right length, and I cut the kitchen paper ones in half. For the copper strips I use sticky-backed 0.05 mm copper foil tape (which you can get online or from electrical stores), and stick two rings of the tape around one end of the cardboard tube, with about 1 mm gap between them. I've found that one ring doesn't work as well, probably as it's not a wide enough barrier and they can arch themselves over it. When planting out, I put the tubes with their copper strips over the young plants, with the copper strips at the top, and work them into the soil slightly to prevent the wind or mice / birds from dislodging them. The copper needs to be at the top to minimise splashes from the soil, which if they coat the strip will affect the conductivity and make it less uncomfortable for the slugs to touch.
I've found that the slugs will not cross a clean copper barrier - I've not seen any instance in two seasons of them doing this. But I have had to be careful of carelessly giving them a bridge from soil to plant in some other way, such as a stake in the earth outside the tube leaning over with its top touching the plant. They seem to be able to spot this sort of oversight very easily, and I've even watched one determined individual tightrope-walking over an 10-inch bit of twine that stretched from a stake to a plant.
Another thing that can affect the effectiveness of the tubes is prolonged wet - they dry out well after short heavy rain but a long wet spell will cause the bases to rot. In the first season of use I treated the cardboard tubes with a spray-on waterproofer, and this did prevent them rotting, but last season I didn't bother and I found that by the time we had prolonged rain in late summer, most of the plant stems were so thick and tough that they didn't appeal to the slugs any more, and the leaves were too high for them to climb up to.
I also tried a few cut-down plastic bottles to make waterproof tubes, and these do last longer, but cutting them up is awkward work, and I prefer to use degradable cardboard and send the bottles for recycling.
I've successfully protected peas, beans, tomatoes, courgettes, squashes, broccoli, calabrese, cauliflower and young cabbages using the cardboard tubes and copper over two seasons. It only works for short-stemmed veg like the cabbages when the plants are young, as the plant obviously outgrows the tube. It costs very little - 20 metres of copper tape costs around £7 and gives me enough for a season, the loo roll centres cost nothing (assuming you use loo roll anyway!) and the cardboard can be put on the compost heap at the end of the season.
What the copper cannot protect at all is root crops, and so far I have found nothing to stop my potatoes, celeriac, beetroot and carrots coming out of the soil looking like colanders at harvest time. I've had to restrict these to growing in bags for now, which works but reduces the crop, so if anyone knows a reliable method for keeping underground keel slugs at bay, I'd love to hear it. Unfortunately Nemaslug treatment is out, as my family have firmly vetoed having nematodes stored in the fridge!
I'm gardening in North Devon, where every exposed surface is covered in moss and lichen, and there seem to be a couple of slugs for every blade of grass on the lawn. I've been here for three seasons now, and in the first year, being used to the drier climate on the east side of the UK, I lost virtually everything, despite having 8 slug pubs on my very small veg plot. But over the last two seasons I've had good success in protecting most plants (except root crops) using copper foil rings on cardboard tubes, which I've put around the bases of the young plants when they get planted out.
I use the cardboard tubes out of the centres of loo roll or kitchen paper - the loo roll ones are just about the right length, and I cut the kitchen paper ones in half. For the copper strips I use sticky-backed 0.05 mm copper foil tape (which you can get online or from electrical stores), and stick two rings of the tape around one end of the cardboard tube, with about 1 mm gap between them. I've found that one ring doesn't work as well, probably as it's not a wide enough barrier and they can arch themselves over it. When planting out, I put the tubes with their copper strips over the young plants, with the copper strips at the top, and work them into the soil slightly to prevent the wind or mice / birds from dislodging them. The copper needs to be at the top to minimise splashes from the soil, which if they coat the strip will affect the conductivity and make it less uncomfortable for the slugs to touch.
I've found that the slugs will not cross a clean copper barrier - I've not seen any instance in two seasons of them doing this. But I have had to be careful of carelessly giving them a bridge from soil to plant in some other way, such as a stake in the earth outside the tube leaning over with its top touching the plant. They seem to be able to spot this sort of oversight very easily, and I've even watched one determined individual tightrope-walking over an 10-inch bit of twine that stretched from a stake to a plant.
Another thing that can affect the effectiveness of the tubes is prolonged wet - they dry out well after short heavy rain but a long wet spell will cause the bases to rot. In the first season of use I treated the cardboard tubes with a spray-on waterproofer, and this did prevent them rotting, but last season I didn't bother and I found that by the time we had prolonged rain in late summer, most of the plant stems were so thick and tough that they didn't appeal to the slugs any more, and the leaves were too high for them to climb up to.
I also tried a few cut-down plastic bottles to make waterproof tubes, and these do last longer, but cutting them up is awkward work, and I prefer to use degradable cardboard and send the bottles for recycling.
I've successfully protected peas, beans, tomatoes, courgettes, squashes, broccoli, calabrese, cauliflower and young cabbages using the cardboard tubes and copper over two seasons. It only works for short-stemmed veg like the cabbages when the plants are young, as the plant obviously outgrows the tube. It costs very little - 20 metres of copper tape costs around £7 and gives me enough for a season, the loo roll centres cost nothing (assuming you use loo roll anyway!) and the cardboard can be put on the compost heap at the end of the season.
What the copper cannot protect at all is root crops, and so far I have found nothing to stop my potatoes, celeriac, beetroot and carrots coming out of the soil looking like colanders at harvest time. I've had to restrict these to growing in bags for now, which works but reduces the crop, so if anyone knows a reliable method for keeping underground keel slugs at bay, I'd love to hear it. Unfortunately Nemaslug treatment is out, as my family have firmly vetoed having nematodes stored in the fridge!