Slug Control
Chemical Options
Metaldehyde
Metaldehyde is a specific molluscicide and will not harm crop beneficials such as carabid beatles and earth worms. Metaldehyde based pellets can affect slugs when ingested, or absorbed through their skin. It works by disrupting cells in the slug's mucus producing membrane, prompting the slug to produce excess mucus in a reaction to expel the chemical, causing it to die. The disruption is irreversible, and slug will not come back to life if in contact with water.
As long as a good quality pellet is visible (TDS, wet process), metaldehyde remains active within the pellet.
Once the pellets has broken down, metaldehyde breaks down quickly into carbon dioxide and water and thus does not leave any long lasting residues in the soil.
Metaldehyde is most widely available in pellet form, and has been used successfully over the last 60 years.
Methiocarb and Thiodicarb
Methiocarb and Thiodicarb fall within a group of chemicals known as carbamates, which number amongst them insecticides and molluscicides. They are most effective when ingested, acting as a broadspectrum neurotoxic and destroying the slug's nervous system. Methiocarb is most readily available in pellet form, but also commercially available as a spray.
Aluminium sulphate and copper sulphate and Iron phosphate
Aluminium sulphate is a contact poison and delivered as a spray directly on to the ground. It is considered 'nearly' organic and has been widely used in this area. It is only really effective against smaller slugs such as the field slug, as it kills through contact action. As aluminium sulphate can build up in the soil, its use is best limited to when slugs are definitely active rather than when numbers are low.
Copper sulphate is also used as a spray and has proved quite successful in combating the field slug, but not so with other species. The chemical also works as a contact poison. Copper sulphate can damage plant and marine life and if being used to control slugs, should be kept well clear of ponds, streams or rivers. Concern has also been expressed about the build up of copper in soil. Copper and Aluminium sulphates are most widely available as powders and largely for the domestic market. They are sometimes favoured by growers as some are less toxic than pellets, although there is some speculation about their efficacy and the build up of the chemical in soil and water. Metaldehyde bridges this gap by offering proven low toxicity while still being wholly effective in control of slugs.
Ferric phosphate is available formulated as a pellet for use on edible and non edible crops