Small actions can help in prevention of Spanish slugs

The Spanish slug is an invasive alien species that has spread widely in Finland. It causes considerable harm, and combating it is therefore important. Spanish slugs are omnivores, and the species has adapted well to the cool climate in Finland. It is especially abundant in Uusimaa and Southwest Finland. Spanish slugs eat many kinds of plants and animals, and can therefore cause considerable damage in both home gardens and fields. Unfortunately, the City of Espoo’s green area maintenance does not currently have resources for combating Spanish slugs. Instead, active assistance from residents is needed in combating the species.

In most cases, relatively small measures are enough to prevent the spread of Spanish slugs. The best time for prevention is in the spring before overwintered slugs lay eggs. One way to control Spanish slugs is to place an old wooden board in the yard and let slugs gather under it. The gathered slugs can then be easily collected.

One effective prevention method is to collect Spanish slugs in a bucket and kill them with boiling water. According to the Vieraslajit website, slugs can also be killed by cutting their heads with scissors longitudinally between the sensory horns or by crushing their heads with sufficient force between a rock and a hard surface. Dead slugs can be collected in containers, such as empty milk cartons. The closed containers can then be disposed of in a normal mixed waste container.

People can also combat Spanish slugs in gardens by using snail bait products such as Ferramol, which is an organic substance used for the prevention of slugs and snails. Ferramol kills slugs without harming hedgehogs, worms, bees or other useful animals. Ducks and chickens eat slugs and can therefore also be used as an effective prevention method.

It is advisable not to touch Spanish slugs with bare hands, as the slugs may spread listeria and E.coli bacteria. Furthermore, to prevent the slugs from spreading, no soil, leaves, compost and plants from areas with Spanish slugs should be transported elsewhere.

Even though Spanish slugs are an unwanted alien species, they should still be treated like any other living beings. Like other molluscs, Spanish slugs have a developed nervous system and the ability to feel pain. They should therefore be killed as quickly as possible, without causing them any unnecessary pain.

Before you start killing slugs, make sure that you can distinguish Spanish slugs from ash-black slugs, a species native to Finland. Spanish slugs are about 7-14 cm long and uniform in colour, usually dirty orange brown or black, whereas ash-black slugs are often black or have black and white streaks. Ash-black slugs and Spanish slugs can also be distinguished by the location of the spiracle; Spanish slugs have it on the front of their shield, while ash-black slugs have it at the back of their shield. In addition, ash-black slugs have a longitudinal ridge on their back, whereas the back of a Spanish slug is evenly convex. More information on identifying Spanish slugs can be found on the Vieraslajit website.

For more information on Spanish slugs and prevention methods for them, please visit the Vieraslajit (external link, opens in a new window)website.

More information on invasive species on the City of Espoo website.