I just this minute saw P. Allen Smith (on weather channel) talk about controlling the slug and snail population from invading the plants. He said that Florida trials showed that when the perennial beds were edged with copper strips sunk into the soil that this method proved very effective. The width of the copper was about 8" deep, length to be determined by the bed of course. He also placed it around individual plants such as hostas, but the depth of the copper was about 4" here. You can also place a band at the bottom of flowering pots and this too deterred the slugs. Apparently copper discharges small amounts of electricity. In order for the copper strips to bend and go round corners, cut into one side of the band all along its length, about one third of the way and approx 3" apart, just as you would do to line a cake tin with greaseproof paper. I hope this makes sense :-) I am definitely going to try this!
I've just recently read that copper works against slugs too. My problem was more my Painted Daisy as opposed to hostas although one kind gets devoured by slugs. Anyway, I'll have to try it too. I had my painted daisy for two years and it barely got to grow let alone bloom before it was eaten away at. So, someone told me about putting broken egg shells around it as the slugs won't crawl through it either. Well, this definitely worked but I can't accumulate enough egg shells to do anything else.
We have the most intelligent slugs in the world here in West Virginia:) Nothing kills them! They even welcome the challenges put forth by us humans:)
I gave up and now just leave them alone...think they are getting bored and most have moved on to bother my neighbors:)
Copper should be closely monitored around fish ponds. If it corrodes to black, green, or blue, these are copper compounds that can build up in the water and kill fish, even some plants. Just keep an eye on it.