After the worst year on record for slugs, things are about to get even worse with millions of a new species of ‘killer slug’ expected to take over gardens this spring.
By Louise Gray / the Telegraph
The monster slugs, from Spain, that can grow up to five inches long, have been found eating dead mice, dog mess and even each other.
The species have already caused havoc in Scandinavia where slugs feasting on road kill caused so much slime it became a road hazard.
The new species, Arion vulgaris, was first identified in East Anglia at the end of last year.
However it has taken until now to confirm the new species is new to the British Isles.
At first scientists thought they could be bigger versions of the slightly smaller Spanish stealth slug, Arion flagellus, that has been in the UK since the end of the last war.
But analysis by dissecting out the male genetalia, which are a distinct taxonomic feature, have confirmed a new species is established in the UK.
It is thought the new species came into the UK via imports of salad leaves.
Ian Bedford, of Head of Entomology at the Government-funded John Innes Centre in Norwich, who found 300 killer slugs in his own garden, said in some locations the new species is even better established than the spanish stealth slugs.
He said that millions of the slugs are set to emerge this spring. The baby killer slugs and eggs are buried under leaves, just waiting to emerge.
“There are almost certainly millions out there,” he said.
“It’s obviously of great concern that we now have this species here. There’s been lots of reports from around the county of massive problems with slugs, which I’m sure are now going to be Arion vulgaris.”
It is already thought that both killer slugs and spanish slugs can mate with native Arion species in the UK – the brown chocolate slug – Arion rufus – or the big black slug – Arion ater
The invasive species could compete with native species, including the smaller grey field slug, that is the most common slug on gardeners’ salad leaves.
Killer slugs eat popular garden flowers like allium as well as vegetables. They also eat potato leaves and could decimate the oilseed rape crop, worth millions to the UK economy.
Dr Bedford said the killer slug can even thrive in dry conditions.
“There are reports of oilseed rape having problems this year which we think could well be because of this Spanish slug. I’ve actually seen them in a potato field in the middle of summer sliming across dry, sandy soil. The agronomist with me couldn’t believe what he was seeing, because slugs don’t usually do that. It’s a hardy species,” he added.
Dr Bedford is now leading research into the killer slugs.
He is collecting information on sightings of large slugs, crops that have been damaged and “unusual incidents relating to slugs”.
He is also looking at whether killer slugs are breeding with native species and whether the species can be controlled using ordinary slug pellets.
“We are using the genome analysis centre at the John Innes Centre to investigate the species and whether we have hybrids. Also whether it is susceptible to sprays and other ways of controlling them.”
A survey by the Royal Horticultural Society found that the most common complaint last year was slugs and snails.
Andrew Halstead, RHS Principal Scientist Plant Health, said many of the sightings may well have been invasive species.
But he said most gardeners will concentrate on extermination, rather than identification.
“For gardeners a slug is a slug,” he added.