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Their Latin name is Arion vulgaris, but they’re better known as the nightmare of many gardeners under their common name, ‘Spanish slug’.
Sometimes in the media, they’re called: killer slug, killer snail or cannibal slug.
The Spanish slug is closely related to common red slugs (Arion rufus) and can mate with them.
The species are therefore difficult to distinguish.

Some people claim that if Spanish slugs were to breed with local species, a sort of ‘super slug’ that could be immune to drought and poison would be created.
Newspapers like these kinds of stories:
‘Foreign invaders wipe out local species and there’s no remedy. Thus, we’re doomed!’
This is just not the case.
There are many remedies, and it’s worthwhile taking a close look at the real reasons behind the population booms:
The loss of biodiversity and the extinction of natural enemies.

Contents
- 1 What Can Be Done? | Spanish Slug Control
- 2 How Can Spanish Slugs Be Recognized?
- 3 Where Did Spanish Slugs Come From?
- 4 Which Plants Do Spanish Slugs Like to Eat?
- 5 Which Plants Are Slug-Resistant?
- 6 When Are Spanish Slugs Active?
- 7 Where to Take Collected Slugs
- 8 Why Can They Multiply So Quickly?
- 9 How Can Spanish Slugs Be Controlled?
What Can Be Done? | Spanish Slug Control
Slug Baits Aren’t the Solution
Most gardeners try slug pellets or beer traps, but at best these methods work for a short time, and often a second, even stronger, wave of slugs comes in.
Unfortunately, violent slug control can only alleviate the symptoms, but this often leads to negative long-term consequences.
Find out why violent slug control doesn’t work:
Why are slug pellets counterproductive?
Video: Spanish Slug Eating a Leaf
Take an In-depth Look at the Roots of the Problem
The first step should be to recognize the root causes of the overabundance of slugs.
Once they’ve been understood, effective countermeasures can be set.
There are two major reasons for slug booms:
1. Natural enemies aren’t present.
2. Plants have lost their defense due to modern breeding.
You’ll find more information here: Causes of and conditions for slug population booms.

Effective Counteractions
1. Attract natural enemies by promoting biodiversity in the garden
2. Use plants that aren’t a favorite dish for slugs.
You’ll find more information here:
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Vegetables and herbs that slugs don’t like to eat | Slug-resistant flowers and perennials |
There are also various barriers that can be used to protect vulnerable plants from slugs.
You’ll find more information here:
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Copper against slugs | Slug fences |
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Slug collars | Slug-repellent paint |
Peaceful Slug Control & Plant Protection
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Slug Repellent Copper Tape | Slug Fence | Protection |
Offer on Amazon | Offer on Amazon |
Offers on eBay | Offers on Etsy |
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Sheep Wool Pellets | Slug Collars | Set |
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Offers on eBay | Offers on eBay |
In addition, some general ways are helpful:
Effective natural slug control.
How Can Spanish Slugs Be Recognized?
Spanish slugs grow up to 4–6 inches (10-15 cm) in length and are very variable in their coloring.
The most common are brownish to reddish, but there are also light yellow to black specimens.

It’s therefore difficult to distinguish them from the common red slugs (Arion rufus) and black slugs (Arion ater).
These three species can mate with each other, which further impedes a clear separation.
However, red and black slugs occur mainly in forests.
Rarely can they be found in the garden, which is where Spanish slugs prefer to stay.
If you encounter a reddish-brown slug in your garden, it’s most likely a Spanish slug.
One clear distinguishing feature between this group of slugs and other slug species is their ability to curl up to protect themselves against their enemies.
Most other slugs, such as the leopard slug, can’t do this. They can contract their body, but aren’t able to curl up.

Where Did Spanish Slugs Come From?
The Spanish slug was first seen in 1954, in Great Britain.
New studies have shown that this slug is not related to species in Spain or Portugal, as was believed for a long time, so it might be more appropriate to call it the ‘British slug’.
Nowadays, it’s believed that the Spanish slug originates somewhere in southern France, from where it’s likely to have spread through most of Europe.
Since the 1990s, the Spanish slug has rapidly conquered more and more areas and has invaded nearly every garden on the Continent.
Because slugs can multiply explosively under favorable conditions, they’ve become a major horticultural pest.
Their exact spread across the Continent is still a research issue and isn’t yet clearly understood.
The common opinion that the Spanish slug was introduced to Northern Europe in the 1960s through salads from Spain is fake.

Recent studies have proven that the Spanish slug has only recently arrived in Spain.
Genetic tests indicate that it’s closely related to Central European slugs.
The first documented sightings are from Great Britain (1954), France (1955) and Switzerland (1956).
In Germany, a specimen was sighted for the first time in 1969 on the north side of the Rhine near Basel.
However, these sightings don’t allow conclusions about their true origin and spread to be drawn.
The slugs’ migration north was probably also favored by climate change and by humans.
It’s believed that they spread mostly embedded in horticultural soils and potted plants distributed around Europe.
As the name ‘Spanish slug’ is misleading, in the future it would be better to find a new name or to stick to its Latin name, Arion vulgaris.

Which Plants Do Spanish Slugs Like to Eat?
The Spanish slug eats mainly fresh plants and carrion.
There are even some plants that they like more than others:
You’ll find more information here: Which plants do Spanish slugs like best?
Flowers as protection against snails & slugs
Click on the image leads to an offer on Amazon.
Which Plants Are Slug-Resistant?
Wild plants are usually spurned when tender flowers or vegetables are close by.
This is because many wild plants still contain protective substances or mechanisms such as tiny thorns, which make them more resilient.
In addition, plenty of humans don’t like the bitter taste of these substances, which is why they’ve been selectively bred out.
Spanish slugs evidently have a very similar taste like many people, which explains why they’re particularly interested in crops.
There are also quite a few garden plants that are still more or less resistant to slug attacks.
You’ll find more information here:
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Vegetables and herbs that slugs don’t like to eat | Slug-resistant flowers and perennials |
When Are Spanish Slugs Active?
Under normal conditions, these creatures are nocturnal and hide in damp, shady places during sunny and dry weather, as they risk dehydration and coming across natural enemies.
Only in humid conditions can they also be found during the day.
The bigger a slug becomes, the more active and drought-resistant it will usually be.
It’s assumed that a slug can travel up to 25 yards (ca. 23 m) per night.
The slugs move at a speed of about 3 meters per hour, so it’s not enough just to throw them over the fence after collecting or to put them some 100 yards (meters) away in bushes.
Slug & Snail Fence | Protective Barrier
Click on the image leads to an offer on Amazon.
Where to Take Collected Slugs
Collected slugs should be taken at least 1,000 yards (meters) away.
They’d then need more than a month to return and are likely to find another spot on their way.
In the long run, it’s recommended to take them even further away.
The best place would be a river or stream that they can’t overcome too easily.
The optimal place would be an island!

Why Can They Multiply So Quickly?
Slugs, like all snails, are hermaphrodite, which means they have both sexes and can even fertilize themselves in extreme situations.
A Spanish slug can lay up to 500 eggs, with up to 225 in a single spot.

The Spanish slug usually dies soon after laying its eggs because, under normal conditions, the species has only one reproductive cycle.
The eggs are buried in damp, dark places, normally directly on the soil but protected from enemies and the weather as far as possible.
Often, they’re stored just below stones, logs, and pots or in the shelter of shrubs and bushes.
Occasionally, you can find their white eggs in cavities under garden fleece or deadwood.
Video: How to Find and Deal with Slug Eggs
In autumn or early spring, it’s worth taking a closer look around and bringing the eggs to the light, where they’re prey for birds and other hungry garden residents.
Depending on the weather conditions, the tiny slugs hatch after a few weeks.
The eggs can also survive the winter and then hatch in springtime.
In addition, some adults can try to hibernate and lay their eggs in spring.
Video: Close-up of Leopard Slugs Hatching
How Can Spanish Slugs Be Controlled?
This is best done by a combination of many methods, as described above.
One often-underestimated means is the installation of slug fences, which are insurmountable to the slugs.
You’ll find more information here:
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Slug barriers overview | Electric slug fence |
What Else Can Be Done?
Attract hedgehogs into the garden.
Protect enclosed and raised beds or greenhouses with slug-repellent paint.
Peaceful Slug Control & Plant Protection
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Slug Repellent Copper Tape | Plant Protection Cover | Set |
Offer on Amazon | Offer on Amazon |
Offers on eBay | Offers on eBay |
![]() | ![]() |
Sheep Wool Pellets | Slug Collars | Set |
Offer on Amazon | Offer on Amazon |
Offers on eBay | Offers on eBay |
Last update: February 13, 2023
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Thank you very much – as well, for sharing and a good rating.
I know you are there, and I am so happy!
Thanks for thorough background info on these creatures but would you mind listing in order of effectiveness how to get rid of them? They are devastating my plants and veg. I have tried mostly picking them off and also bio slug pellets but am now totally overrun with them.
Help!
Hello Dot,
thank you for your comment!
Here you find some help: how to control slugs.
May you enjoy your garden!
Alex
How do slugs end up in the sink even though plugs are in overnight in Spain?
Hi Alex,
I wonder if there are nematodes for this species?
Thanks,
Dot
Hi Dot,
to my knowledge nematodes only work for slugs that live underground (Agriolimacidae – Deroceras).
Here you can find more information on nematodes: nematodes against slugs.
May you find a peaceful way to protect your plants!
Alex