This invasive species is wreaking havoc in European gardens. Here's what the experts recommend.
A Spanish slug, also known as a killer slug.(Photo: Berit Roald / NTB)
NTB.Norwegian news agency
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Both local newspapers and VG have recently reported large numbers of Spanish slugs in Lillestrøm, Tvedestrand, Fredrikstad, Steinkjer, Lillehammer, and Tønsberg.
"You can't get rid of them completely," says communications adviser Erling Fløistad at the Norwegian Institute of Bioeconomy (NIBIO).
The reason is that Spanish slugs can lie dormant underground for months, only emerging when they feel like it and moisture levels feel right. That's why you won't find them all at once.
Nevertheless, NIBIO researchers have several tips and tricks to limit the damage Spanish slugs can do in your garden. Fløistad recommends removing as many as possible, since they can lay a large number of eggs in August.
1. Find their hiding places and clear them
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Slugs are like trolls – they hide before the sun comes up. Therefore, Fløistad advises taking an evening walk, cutting the slugs you find along the way, and noting where they hide.
Ideal hiding places include stone piles near houses, which can be covered with sand. They also like stacks of wooden planks, so tidying these is helpful. In overgrown areas, mow the grass or pull weeds, then cover the area with bark, advises Fløistad. This makes your garden less welcoming to slugs.
2. Don't clear the entire garden
"The reason for using these evening walks to find the slugs is to locate the hiding spots the slugs actually use and clear only these areas," he says.
Fløistad cautions against clearing the entire garden, as this can destroy habitats for beneficial insects that help control the slug population.
3. Cutting is the recommended method of extermination: "Salt is slow torture"
The most humane and effective method to kill Spanish slugs is cutting them in two, according to Fløistad.
Using salt, ammonia, or artificial fertiliser, on the other hand, is slow torture.
"For quick and humane extermination, use boiling water. Keep a bucket of boiling water on hand and drop the slugs into it. They die quickly," biologist and researcher Bjørn Arild Hatteland at NIBIO previously told NTB.
