Slugs and snails love the fresh leaves of your dahlia plants. With copper tape, you can make snails, slugs and ants turn around immediately. Stick a strip of copper tape on the edge of a pot or container or around a ring that you place around a small plant. If snails walk on it, it will shock them and they will take a different route. Ants do not like the smell of copper and it disturbs their scent trail.
This roll of tape is 5 meters long and 3 cm wide. You can cut it to size with scissors. Make sure that the surface is dry and clean, then the copper tape will stick best.