Slugs and Snails

• Slugs and snails may be a pest to many gardeners, but they often only eat decaying vegetable matter. They are also the food of many birds and mammals. So protection of your soft young plants is better than trying to get rid of the molluscs.
• Baits can be used to control slugs and snails.
• Some baits are very toxic to other animals and should be used and stored with caution.
• Iron phosphate baits are safer if pets or children are present.
• Traps can be useful ways to control slugs and snails.
  • Place upturned pots or pieces of board in the affected areas leaving enough space below for the slugs and snails to get underneath. Then regularly check for hiding molluscs and remove them.
  • Dig a hole for a jam jar and set it so that the lip of the jar is a soil surface level. Add a little beer to the jam jar. It will soon fill with slugs and snails which can be removed.
• Remove weeds which would provide shelter for slugs and snails during the day.

Methods that reduce slug and snail numbers suffer from a fundamental flaw in 'ignoring' their biology. Slugs and snails control their own population. They lay enormous quantities of eggs, when hatched; most slugs and snails remain as relatively harmless juveniles. As slugs and snails move about, they leave behind trails of slime. Only when the density of slime trails falls will more juvenile slugs and snails develop to adults - which is exactly what happens as soon as a significant number of the creatures have been killed, so the numbers of large damaging gastropods are replenished rapidly and during growth, and development of the juveniles will cause more plant damage as they eat for growth. So the more slugs and snails you kill with slug and snail bait the more slug and snail bait you need to use!

Also, baits are only attractive to slugs and snails over very short distance (c 5cm) i.e. baits must be spread and numerous so that slugs and snails will be likely to encounter them. And slugs and snails eating sub-lethal doses will become bait shy; stop feeding on the baits. Molluscs produce an alarm pheromone when distressed, e.g. when eating toxic bait. This will prevent other molluscs feeding in that local area, so there is no point having baits large enough to kill more than one mollusc.

What does this mean for slug and snail control?

Baits are a self-perpetuating control method; once you've started it is hard to stop. Prevention is better than cure so consider changing the conditions so that they are not suitable for slugs or snails and using repellents. Slugs and snails prefer damp conditions in and amongst leaf litter or dense vegetation so rake out leaf litter and keep clear open areas around susceptible plants.

Copper bands can be fitted around raised beds to keep slugs and snails away and crushed egg shells, diatomaceous earth, coffee grounds, wood ash and other natural substances have been shown to be repellent to slugs and snails.

Keep them out rather than kill them.