Certain slugs can eat entire vegetable beds, and even hanging containers are not safe. The situation is particularly bad at the moment, say experts.
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It has been a much-discussed topic in hobby gardening forums for weeks: Plants that have been painstakingly grown are eaten down to the stump by slugs overnight. This year, it is said, there are an incredible number of them – an impression that experts confirm. “Yes, it is bad this year,” says Michael Schrödl from the Zoological State Collection Munich (ZSM).
“After the drought years from 2018 to 2022, in which the populations collapsed accordingly, we now have the second very wet year in a row,” explained Markus Pfenninger from the Senckenberg Biodiversity and Climate Research Center in Frankfurt. The populations had already recovered last year and were able to start this year from an already high level. The mild winter certainly didn't do any harm either – “but according to our observations, only extremely cold winters have a really lasting negative impact.”
If the lettuce disappears and glittering slime bands spread across the beds, it was probably the Spanish slug at work. The technical name is Arion vulgaris, also known as the large garden slug. It is found in many places – but only very sporadically in Spain, as researchers have discovered in recent years. Contrary to what was long assumed, it was probably not introduced from the Iberian Peninsula through fruit and vegetable imports after the Second World War – so the name is misleading.
In fact, the species has probably been around for a very long time – at least in southwest Germany. Since the 1960s, it has been appearing more and more north and east, often in high densities. To the chagrin of gardeners, these are real super snails: the brownish-reddish animals are excellent climbers, and raised beds are no problem for them, as Michael Schrödl once explained. Even a high-hanging container does not stop them: they rappel down on the slime thread. They can smell lettuce and vegetables from dozens of meters away.
Dry lawns and gravel paths may be a problem for other native slugs, but not for Arion vulgaris. According to experts, it reproduces faster, eats more and, if necessary, sits in the blazing sun to feed without being harmed. In addition, genetic analyses show that it mixes a lot with other species – and in this way possibly acquires new, beneficial characteristics for the respective environment. And as if that were not enough: a fully grown Arion vulgaris has hardly any predators of interest – apart from Indian runner ducks. Some ground beetles can also eat young slugs or their eggs.
Some hobby gardeners are currently stating in forums that they collect dozens or hundreds of slugs every day. According to Pfenninger, part of the problem is probably that there are fewer and fewer animals that eat young slugs, such as hedgehogs and toads. “Arion vulgaris is profiting from the desertedness of gardens,” said Schrödl.
A common measure against slugs is the beer trap. However, this tip is rather counterproductive. The smell of fermentation attracts slugs into the glass, where they then drown. However, the pests are also attracted from neighboring gardens – and on the way to the trap they cause severe damage to the vegetable and flower beds. In addition, the beer trap also attracts slugs, which are considered natural enemies of slugs (more on this in this article here). The barley juice is therefore not a suitable measure in the fight against slugs.
Better remedies against the snail plague, however, are nematodes and, of course, natural gardening, which will bring the mollusk's predators into your garden.
It is therefore more effective to only water in the morning, to surround beds with sand strips or snail fences and to regularly turn potential egg-laying sites such as boards lying on the ground out into the sun to dry them out. And of course to collect them. Proper disposal is important afterwards, because the pests quickly crawl out of the organic waste bin and compost and then spread again throughout the garden. And releasing them in the forest is not an option either, because they also cause damage there.