Snails and slugs are troublesome pests that can cause serious damage in the garden. They love cool, moist weather and feed at night or on rainy days, so they usually go unseen when they are doing their damage. Snails and slugs avoid hot, dry weather and bright sunlight, they hide in damp places during the day to avoid predators, as they’re too slow moving and vulnerable. They are commonly found hiding under upturned flower pots, dense groundcover plants and any debris in the garden.
A study by Dr Dave Hodgson, associate professor of ecology at the University of Exeter in the UK revealed that the top speed of a snail is a sluggish one metre per hour but they will travel distances of up to 25 metres in a 24-hour period, and seek out areas of shelter overnight. That is enough range to cover most backyards!
Damage
Snails and slugs feed on a both living plants and decaying plant matter. They cut holes in the middle of leaves, eat seedlings completely to the ground, and also attack ripening low-hanging fruit such as such as strawberries and tomatoes.
The foliage and fruit of some trees is also eaten by snails and slugs. They are quite competent at climbing vertically and they do have a preference for the young leaves of citrus trees. [1]
It’s possible to distinguish snail damage from caterpillar damage, because caterpillars only eat leaves from the edges, whereas snails and slugs have rasping tongues which can also cut holes in the middle of a leaf. Another tell-tale signs of snail and slug damage is the identifying shiny silver trails they leave behind.
Prevention
- Handpick to reduce their numbers – seek them out in their favourite hiding places e.g. strappy leafed plants and ‘do the stomp’ on a wet night.
- Eliminate any hiding spots near your garden such as tall grass and weeds along fences, rotting logs and wood piles where possible.
- Create a less favourable habitat by using drip irrigation rather than sprinklers to reduce humidity and moist surfaces.
- Grow sacrificial plants such as horseradish as a decoy to direct the snails away from other plants.
First option
- Use barriers to protect vulnerable plants – crushed eggshells, lime, wood ash, coffee grounds, wood shavings, or sawdust. The best barrier is copper banding around plants or pots.
- Spray a strong coffee brew on plants and soil – 10 parts water, one part espresso coffee (because instant coffee is too weak).
- Make traps – use boards raised slightly off the ground, inverted flower pots, citrus halves open end down, leave overnight and scrape off snails in the morning. Beer traps can work, it’s the fermented materials that attracts snails and slugs, so a mixture of sugar-water and yeast mixture can be used instead of beer, these traps aren’t very effective for the work involved.
- Mulch the area with some strong smelling herbs like wormwood, mint, tansy or lemon balm.
Last Resort
- Snail and slug baits should be used in conjunction with the IPM cultural controls detailed above for maximum effectiveness.
Use snail baits based on Chelated Iron/ Iron EDTA complex (coloured red/brown), as these are safer to use around children and pets such as dogs and cats. The active ingredient is rated less toxic than common salt, but if consumed in large quantities it may be toxic. If snails and slugs consume even a small amount of this bait, they will stop feeding and die several days later.
Many snail and slug baits are based on either:
- Methicarb – (coloured blue) moderately mobile in soil (potential to move off the site of application) and highly persistent, highly toxic to bees, fish, birds and mammals; or
- Metaldehyde – (coloured green) highly mobile in soil (potential to move off the site of application) and highly persistent, moderately toxic to fish and mammals. Note – If cool, wet weather follows application baiting, the pests can recover if they ingest a sub-lethal dose.
Both are considered a high toxicity risk to domestic animals, wildlife and children.
NOTE: Don’t use metaldehyde snail baits where children and pets could encounter them.
NOTE: Never apply these baits in a pile, this makes them more attractive to pets and children and is not as effective as sprinkling the snail and slug bait.
The best time to apply snail and slug baits is when they are active and feeding, you can encourage them by sprinkling the area with water first, then applying the bait in the late afternoon or evening. Keep in mind that snails and slugs aren’t active during the hottest and driest or coldest periods.
The best places to sprinkle these baits is around their hiding places, and along the path they cross to get to the garden, as well as the garden itself.
[1] University of California Division of Agriculture and Natural Resources Statewide Integrated Pest Management Program, Pests in Gardens and Landscapes – Snails and Slugs (http://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html )
