Copper can be used in many forms to control infestation of microorganisms like algae, bacteria, mould and fungi as well as those we can see like slugs and snails.
The copper penetrates the membranes in microorganisms and disrupts enzymes, causing them to die. When slugs and snails crawl over the metal, a chemical reaction occurs which causes unpleasant feelings on their skin, so they avoid it.
Many forms are considered safe to use in organic operations and around pets and wildlife if used as directed.
The two liquid forms you will often see are copper ammonia diacetate complexes or Bordeaux mixtures (copper sulphate and lime).
For slug control, one of the easiest forms to use are copper barriers like foils placed vertically to form a physical barrier.
Copper screen foils like the one pictured should be pushed into the soil a few centimetres to ensure that slugs and snails do not burrow underneath.
Copper foils and tapes can be reused. Use a vinegar solution to clean tarnished or dirty copper barriers and ensure their continued effectiveness.
Choosing these types of barriers and controls are long lasting, non-toxic and avoid tissue damage to plants that may occur with some controls.