Beer traps for slugs: a very bad idea

A cold chill runs down your spine when, the next day, your garden is nothing but a miserable no-man’s-land, overrun with slugs that your seedlings weren’t enough to satisfy.

Fortunately, as an unexpected response to your dismay, a friend shares with you a highly effective technique for getting rid of slugs: the beer trap!

STOP! We stop everything! It’s a really bad idea! The beer trap is a technique to be avoided– for you, for your plants, and for most of the creatures in your garden.

Let’s see why:

I. How the beer trap works, for slugs

a. Why are slugs attracted to beer: is it the alcohol that attracts them?

But then, the first question I asked myself was: what attracts slugs to beer? Is it the alcohol? Would it also be possible to adapt the traps? Red wine traps in Nouvelle-Aquitaine, dry whisky if you have a Scottish soul, or a little Pastis if you like to play pétanque and nap under the cicadas?

Actually, no! Slugs won’t drown in Pastaga like Dédé in front of an OM match.

For the ladies, what attracts them is the flavors of hops, so dear to our friends in Brittany, Alsace and Belgium.

In fact, they confuse the smell of hops with that of Chicory, which they love!

Smelling the delicious scent, slugs swarm from afar, sometimes falling into the trap.

b. Can you trap slugs with alcohol-free beer?

You’re in detox, and there’s no alcoholic beer left in your fridge? Wondering if a slug trap also works with non-alcoholic beer? Even if you’ve dutifully read the first part of this article, you might wonder whether the alcohol in beer comes from the hops themselves? What if the latter were replaced by artificial flavors?

So, when I look at the composition of the first alcohol-free beer I come across, it says:

• Water
• Barley malt
• Natural aroma
• Hop extract

Now you have the answer to your question! There are hops, so it works in the same way as a classic beer 😉

b. How a classic beer trap works, for slugs

For those who don’t really know what it’s all about: a beer trap is simply a beer dish placed (sometimes semi-buried) in the garden. Slugs, attracted by the smell, come and take a few sips, and once drunk, fall in and drown. Yes, it’s creepy.

II. Why is the beer trap an ineffective, even counter-productive, method?

a. The counter-productive consequences of beer’s attractiveness to slugs

As we said, slugs love the smell of hops diffused by beer on contact with the air. Slugs have very poor eyesight, and find their way around their environment mainly by their highly developed sense of smell.

And it’s this super-developed sense of smell that enables slugs to smell beer from a distance of just over 100 m!

It’s going to be a brown gold rush. Within a 100 m radius of your garden, all the gastropods craving a little glass of hops will start running (at 2 m/hour) towards your gate. An ultra-slug-trail and 50 hours later, the whole neighborhood will be in your backyard.

The advantage is that your neighbors will start to like you a lot. Their hostas, dahlias and zinnias will regain their vigor.

The downside is that you’re likely to have a gastropod fair at home: don’t expect all the slime to drown. In fact, it turns out that only about a third of slugs end up drowning in beer. The others just have a drink, and go off to tend your salads. (See the video below, where you can see that most of the slugs go away quietly).

b. Beer traps: why do they harm the slug predators needed to regulate the problem sustainably?

Well, let’s say you’re still interested in the idea of using a beer trap (for example, if you have a garden measuring more than 100 x 100 metres (1 hectare), you might still be interested in this method). Then there’s the fact thata beer trap has “side effects” on a much larger time scale. That’s what we’re going to look at here, with the impact of a beer trap on slugs’ natural predators.

i. The impact of a beer trap on slug predators

There are many insects that predate slugs: staphylins, glowworms, but above all carabid beetles, for example.

These insects, as predators, are attracted by the smell of slugs.

They’ll be prospecting near the beer traps, and there’s a good chance they’ll fall in. Once they’ve fallen into the beer dish, these insects have virtually no chance of escaping.

One carabid beetle drowned in a beer trap means many slugs thanking you warmly. With several carabid beetles drowned in a beer trap, the balance of this species in your garden may be threatened: fewer offspring, which means fewer carabid beetles next season, etc. Fewer carabid beetles in your garden means potentially even more imbalance in an already imbalanced garden (because an abundance of slugs is merely the symptom of a systemic imbalance that needs to be corrected).

ii. The impact of a beer trap on hedgehogs, slug predators

If the beer trap endangers the smallest of our “allies”, it also endangers the biggest.

The use of beer traps can be very unfavorable for hedgehogs.

Firstly, their food is likely to be scarcer within a 1 hectare perimeter.

So they risk :

• Either come and eat the slugs in your beer trap: as the slugs are full of alcohol, they’re likely to get drunk too. A drunk hedgehog can no longer curl up into a ball to protect itself from predators, it can drown by falling into a small pool of water or puddle, and, disoriented, the risk of being run over on the road increases.
• Or to move to a place richer in prey.

In both cases, the risks of losing (or causing the loss of!) this garden ally are significant.

iii. The danger of a beer trap for leopard slugs

Not all slugs are a threat to your vegetable garden! Leopard slugs, for example, are predators of other slugs (they even chase them!).

These too, attracted by the smell of drowned slugs, risk falling into the beer trap and drowning.

iv. Beer traps unbalance prey-predator balance

The side effects of this “anti-slug method” are numerous. In general, “eradication” methods should be avoided if you want a balanced, self-sufficient garden. Extermination methods of this kind often only lead to a yo-yo effect: it’s the story of the prey-predator balance: kill the prey, and the predators will leave or starve. With no predators, prey is once again plentiful. Once again, we eradicate… and off we go again…

Conclusion:

The success of the beer trap is probably due to the fact that the “result” (dead slugs) can be observed, whereas the effect of other solutions is more complicated to observe.

But let’s not be fooled by this cognitive bias (due to what we call “ignorance of absence”), because the harmful side-effects of beer traps are undeniable : they attract all the slugs in the neighborhood to your garden, kill or relocate natural predators, and thus have a yo-yo effect and hinder long-term natural regulation, among other things…

The same yo-yo effect as when using slug pellets, salt or other lethal methods. (See:  salt against slugs – don’t do it!)

And yet, the beer trap is a slug control method that’s often used, but also relayed .

What a pity people aren’t more informed on the subject!

What a shame to turn to this type of method when alternative solutions exist that are more effective and respectful of the living beings in our garden!

I hope that, having read this article, you feel better informed on the subject, and that you’ll be able to make the choice that seems right to you!

Even better! Follow scrupulously these 7 steps 👇

This is the action plan I devised following the findings of dozens of scientific studies on the subject.

I owe the success of my cabbages, salads, strawberries and cucurbits to it.

Click here to find out more:

Related articles:

• Slug pellets with baking soda?
• Beer traps: a bad idea
• Don’t make the mistake of using salt against slugs

Bibliography :

• Kozłowski, J., Kozłowska, M., & Kotowska, A. (2014). Beer as olfactory attractant in the fight against harmful slugs Arion lusitanicus Mabille 1868 / Piwo jako atraktant w zwalczaniu szkodliwego ślimaka z gatunku Arion lusitanicus Mabille 1868. Folia Malacologica, 22(4), 271-276.

• Scaccini, D.; Panini, M.; Chiesa, O.; Nicoli Aldini, R.; Tabaglio, V.; Mazzoni, E. Slug Monitoring and Impacts on the Ground Beetle Community in the Frame of Sustainable Pest Control in Conventional and Conservation Agroecosystems. Insects 2020, 11, 380

• https://www.slughelp.com/beer-traps-slugs-snails-experiences-alternatives/ – an excellent site, which I recommend.