By Calvin Jones

Slugs have been present in the British Isles since the end of the last ice age. They are members of the mollusc family and, along with snails, belong to a large group of molluscs known as gastropods. The name literally means “belly-footed”, and refers to the broad tapered foot on which these creatures glide.

Essentially a slug is a land-snail without a shell, although many species retain shell remnants internally. Gastropods originated in the sea, and those that have moved onto land remain very susceptible to loss of moisture.

Without a shell, slugs have no built in shelter to help them conserve water, so they tend to find a cool, damp retreat during the day, emerging only at night to feed.

Contrary to popular belief not all slugs feed on healthy young plants: in fact it’s only relatively few species that give the group a bad name as garden pests. Some species are carnivores, actively hunting invertebrates, including other slugs, but most feed on dead or decaying plant matter. These slugs play an important role in a healthy ecosystem, helping to break down dead plant material making the nutrients available to other plants and to their many predators.

One of the worst culprits in terms of attacking garden plants is the grey field slug (Deroceras reticulatum), which is active above and below ground whenever the weather is wet enough, even on milder winter days.

These small grey slugs can decimate young seedlings. Recent research shows that they actively select leaves with a high nitrogen content, so excessive feeding of young plants will only encourage further slug attack. They have also been shown to exibit a “memory” effect, which will bring them back to the same patch night after night until an entire crop of seedlings is destroyed.

Continue reading in this week’s Ireland’s Own