Amsterdam releases 5,000 leaf fleas to halt Japanese knotweed spread

Government issues exemption to alien species ban in attempt to control destructive plant

Five thousand Japanese leaf fleas have been released in Amsterdam to combat Japanese knotweed, a once celebrated plant the concrete-breaking roots of which now threaten local biodiversity, impinge on water quality and increase the risk of flooding.

The Dutch government made the unprecedented decision to issue an exemption on a ban on the introduction of alien species in the face of spiralling costs related to the invasive species.

The Japanese knotweed, Fallopia japonica, is causing major damage to building foundations, pavements and dykes in the Dutch capital, costing millions of euros a year. Laboratory tests suggest the leaf fleas – Japanese knotweed psyllids, or Aphalara itadori can kill young shoots and potentially stop the plant growing by sucking up its sap.

An initial 5,000 fleas have been released in three field locations. It is hoped they will successfully hibernate over winter and establish themselves in the new year. Further specimens will be released next spring.

The Japanese knotweed was introduced and cultivated in the Netherlands as an ornamental plant between 1829 and 1841 by the German botanist Philipp Franz von Siebold. Discovered by the side of a volcano, it was named as the “most interesting new ornamental plant of the year” by the Society of Agriculture and Horticulture in Utrecht.

Its aggressive roots, which can grow up to 20cm a day and break through concrete or tarmac, have since been a major issue across Europe. Amsterdam has previously looked at using fire, hot water and even laser in controlling the plant’s growth without success.

Suzanne Lommen, an entomologist at the Institute of Biology in Leiden, the southern city where the Japanese knotweed was first introduced in the Netherlands, is coordinating the trial.

She said: “All sorts of things have been tried, but complete pest control is extremely difficult and very expensive. We will have to combine various methods to get the Asian knotweed under control. We know from the Japanese knotweed psyllid that it can kill young shoots and slow down or even stop the growth of the plant by sucking up sap – nutrition – from the plant.

“If the psyllid can establish, reproduce and spread, and do the damage we see in the breeding trials, it can hopefully inhibit the growth and spread of Asian knotweed. Then you have a very cheap and environmentally friendly solution with many years of effect that you can combine with the more expensive methods.”

The Netherlands Food and Consumer Product Safety Authority (NVWA) has concluded the psyllids do not pose a threat to native biodiversity.

Jaike Bijleveld, from the municipality, said there were a thousand sites in Amsterdam where knotweed had taken hold. “It’s a really big problem, but we’re working hard on it,” she told the Amsterdam newspaper Het Parool.

Lommen said there was a chance the fleas would not take to the Dutch climate. “What we do not know yet is how the psyllid will thrive in the Netherlands,” she said. “It comes from an area in Japan where the climate most resembles that of the Netherlands. In the laboratory, it thrives on the interbreed knotweed that grows here. But reality will show whether it can survive in our country.”


Daniel Boffey

The GuardianTramp

Related Content

Article image
Alien v predator: moth out to kill Japanese knotweed

Chosen insect feeds on invasive species but not other closely related plants and crops

Juliette Jowit

09, Mar, 2010 @12:05 AM

Article image
Utrecht rooftops to be ‘greened’ with plants and mosses in new plan
‘Vertical forest’ tower will have 10,000 plants on its facade in bid to reinvigorate biodiversity

Daniel Boffey in Brussels

27, Mar, 2020 @2:02 PM

Article image
Invasion of the monster plants
Country diary: The Chevin, Otley, West Yorkshire The most prolific plants spring up to monstrous heights and otherwise orderly places become twisted and tangled

Carey Davies

05, Sep, 2016 @4:30 AM

Article image
Cyprus begins lionfish cull to tackle threat to Mediterranean ecosystem
Voracious fish are bleeding into ocean ‘like a cut artery’, says top marine biologist

Helena Smith in Nicosia

29, May, 2019 @11:25 AM

Article image
Human activity is driving Earth's 'sixth great extinction event'
Population growth, pollution and invasive species are having a disastrous effect on species in the southern hemisphere, a major review by conservationists warns

Ian Sample, science correspondent

28, Jul, 2009 @6:24 PM

Article image
Asian wasp listed as threat to UK's sweet chestnut trees
Forestry commission elevates oriental chestnut gall wasp to high-priority tree pest after 2015 outbreaks

Adam Vaughan

26, Apr, 2016 @2:22 PM

Article image
Raccoon, mongoose and cabbage among invasive species banned from UK
New EU regulation blacklists 37 non-native plant and animal species in a bid to tackle threats to native wildlife and economic losses

Jessica Aldred

02, Aug, 2016 @1:24 PM

Article image
Amsterdam to ban petrol and diesel cars and motorbikes by 2030
Diesel cars older than 15 years will be barred next year as first part of anti-pollution drive

Daniel Boffey

03, May, 2019 @9:53 AM

Article image
Ale of an idea: Amsterdam unveils King's Day urine plan
Water board aims to provide model of sustainability by collecting byproduct when orange-clad revellers take the pils

Jon Henley European affairs correspondent

25, Apr, 2016 @5:27 PM

Article image
Netherlands puzzles over death of estimated 20,000 guillemots
Scientists yet to figure out how the birds died after hundreds wash up on Dutch coast

Daniel Boffey in Brussels

06, Feb, 2019 @10:57 AM