New Guinea flatworm: Foreign worm that could wipe out Britain’s snails arrives in Europe via potted plant imports

Experts want imports of pot plants banned to keep highly destructive species out of Britain

Environment editor

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Imports of pot plants should be banned to keep out a highly destructive flatworm that threatens to wipe out the entire snail population, a top British insect expert has warned.

The New Guinea flatworm is set to become the latest “harmful non-native species” to enter Britain under the cover of plants brought in from abroad, after being spotted in Europe for the first time this month. Mr Shardlow said the rapid growth in international trade in potted plants had accelerated the spread of “harmful non-native species” as eggs and insects cross borders by passing under the radar in soil, foliage and branches.

“A flatworm that overwhelms snails in a ‘gang attack’ and has caused many extinctions when introduced to other parts of the world has now arrived in Europe. Urgent action is necessary to save wild British snails – the UK government should close the borders to pot plants,” he said. It is extremely difficult to detect eggs and small bugs in pots, which can be devastating when introduced to alien environments, wreaking havoc on gardens, forests, farmland and ecosystems by upsetting the balance of nature.

“It only takes one or two eggs in a pocket of air deep in the soil to survive and a potentially devastating invasive species has crossed over a border and threatens a new country, where there is no strategy to deal with the invader,” Mr Shardlow said.

“There is no need to import pot plants into the UK – horticulturalists here are quite capable of growing our own pot plants and selling them on the domestic market,” he added.

Potted plant trade is the likely source of species such as The New Zealand flatworm, which has significantly reduced worm populations in the northern British Isles, which play an essential part in aerating and fertilising the soil. Other examples include the Harlequin ladybird which consumes native ladybirds and the Spanish slug, which was first spotted in the UK last year, Mr Shardlow said. The Spanish species is larger, reproduces faster and is more resistant to slug pellets than UK species and is eating its way through gardens and crops. Concerns are mounting that it they could breed to produce a super-hybrid.

But the biggest fear surrounds the prospect of invasion by the New Guinea flatworm. “This species is extremely invasive. I really hope it can be stopped at the earliest stages,” said Jean-Lou Justine of the National Museum of Natural History in Paris, adding the threat was so great that “all snails in Europe could be wiped out”.

A government spokesman said: “We do not believe that there are any New Guinea flatworms in the UK but we are aware of the threat they could pose to our native wildlife. We are currently assessing the risk and will then consider the most appropriate action.”

Nor is the New Guinea flatworm the only vicious species poised to enter the UK via the international pot plant trade, Mr Shardlow warns. The Asian hornet, a bee-eating wasp already destroying bee populations is high on his list of insects to fear, as is the Argentine ant – “one of the worst invasive species in the world, eliminating native ant species and damaging ecosystem”.

Mr Shardlow is not alone in his concerns about harmful invasive non-native species. Graham Madge, of the RSPB, said: “We are extremely concerned about the threat of non-native species becoming established in the UK. This has very serious impact on wildlife and could be extremely damaging to the economy.”

“The problem is accelerating in line with international trade, partly because of the Internet which has significantly increased the volume of plants being shipped around the world,” he added.

Mr Madge says rising trade is part of a “potential nightmarish cocktail” – the other part being climate change, which makes it increasingly possible for invasive species such as termites to colonise the UK.

Invasive species fall into three broad categories, according to Mr Madge. There are those that come in “under the radar”, for example nestled in plant pots and  those – such as mink – that are brought into confined fur farms and escape and breed. Finally, there are those that are brought over and widely released and cause unintended problems – such as the grey squirrel, which was imported from American in the 19th century as a fashionable addition to estates and proceeded to the native grey squirrel population. Last week ministers finally conceded defeat in their battle against the grey squirrel by scrapping laws requiring people to report their presence on their land so they can be destroyed.

Robin Gill, a vertebrate ecologist at Forest Research, an agency of The Forestry Commission, put the damage inflicted by the grey squirrel on Britain’s timber industry at well over £10 million a year from bark stripping alone.

Those losses result from the lower price fetched by the damaged timber and is one of several reasons why woodland owners are increasingly unwilling to plant new trees, Mr Gill says.

“In the last year I have become increasingly aware of woodland owners not wanting to plant new trees because they feel it isn’t worth it.

“They are increasing worried about climate change, grey squirrels and a proliferation of diseases such as chalara fraxinea (ash dieback) because of the growing global trade in plants and plant products. These provide a strong disincentive to plant and the economic effects could be enormous,” he said.

Farmers are also concerned. “The changing climate means that species historically not able to reproduce in the UK, suddenly can do so,” said Guy Gagen, chief arable advisor at the National Farmers Union, noting that invasive species such ring rot in potatoes “can be very serious”.

Invasive non-native species cost the British economy an estimated £1.7 billion a year, most of it in agriculture and horticulture, according to a government report, which notes that the true cost is likely to be significantly higher because it doesn’t measure “damage to ecosystem services and loss of biodiversity, which cannot be readily quantified”.

Most experts agree that the threat posed by non-native species is clear. However, some believe there is some cause for hope, not least because the European Commission has acknowledged the scale of the threat and is working on “an action plan to protect biodiversity against problematic invasive species”.

“The country is under an unprecedented threat from tree pests and diseases after an exponential rise over the last decade. If we don’t do anything that rise will continue. But I am impressed by how everybody is recognising this as a problem and pulling together. Some things you can’t stop but others you can. So we face a big threat but it is possible to curb it,” said Ian Wright, the National Trust’s gardens advisor.

Britain’s deadly pot-plant bug imports

Harlequin ladybird (Harmonia axyridis) – It has taken less than five years to spread across the whole of the UK, consuming our native ladybirds and causing a nuisance in people’s houses in the autumn

Oak processionary moth (Thaumetopoea processionea) – strips whole oak trees bare of leaves leaving them vulnerable to attack from other pests and diseases. Has very irritating hairs that can cause skin rash for humans and stimulate the Forestry Commission into spraying woodlands with toxic pesticides that damage ecology.

New Zealand flatworm (Arthurdendyus triangulates) – a predator of our earthworms that has spread into the wild in parts of Northern England, Scotland and Northern Ireland. Its impacts have been particularly heavy on our most ecologically important earthworm the Lob worm.

Lily beetle (Liloceris lilii) – a shiny red beetle that people like until it eats all their lillies. They first came to Britain in the 1930s.

Spanish slug (Arion vulgaris): A huge slug spreading through Britain’s gardens and causing havoc. It is bigger and more resistant to slug pellets than UK species and the concern is that the two could breed to produce a super-hybrid slug.

Light brown apple moth (Epiphyas postvittana) – One of the commonest garden moths in many areas but the shiny orange-brown headed insect is so far only causing minor problems in the UK– imported from Australia.

Rosemary leaf beetle (Chrysolina Americana) – a frankly beautiful beetle, but not all rosemary growers agree with me. The beetle, which became an established pest in Britain in the 1990s, also eats the leaves of lavender, thyme and sage.

And three to beware of

New Guinea flatworm (Platydemus manokwari): A horror that has destroyed populations of native snails across the Indo-Pacific that has just been found in Europe for the first time, in France. It is considered to be the cause of extinction of native land snails on several Pacific and Pacific Rim islands.

Asian hornet (Vespa velutina) – a bee-eating wasp already destroying bee populations in France. It is expected to cross into the UK, initially settling in the southern parts of the country. It is regarded as a highly effective predator of insects, posing a significant threat to ecosystems.

Argentine ant (Linepithema humile) – one of the worst invasive species in the world, eliminating native ant species and damaging eco-systems. Its workers are extremely fast moving and industrious, often recruiting in high numbers.

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