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South American weevils released into UK waterways to control invasive weeds | Invasive species

South American weevils have been released into UK waterways by the government to combat the invasive floating pennywort.

The industrious insects are heralded as hope to cut down the weed, which grows rapidly and covers rivers and canals, drowning out light and smothering life within.

Water pennywort was imported from North America as an ornamental plant. It can grow up to 20cm per day, forming dense rafts over rivers that not only harm biodiversity, but disrupt recreational activities such as fishing and canoeing, and exacerbate flood risk. .

It is very unusual to release non-native species into the wild to control invasive species, and this is the first time that biological control has been used to control water pennywort.

The Floating Pennywort on the River Weaver in Cheshire. Photograph: Pat Bennett/Alamy

When asked if the release could turn into an old woman swallowing a fly situation with the weevils then having to be checked, officials assured the Guardian there had been a decade of safety testing of liberation. The government has also stressed that weevil discharges are strictly controlled and require a license from the Environment Agency.

Richard Benyon, Minister for Biosecurity, said: “It is important that we tackle invasive non-native species to protect our native plants and animals and safeguard our environment, our economy and our health.

“We all have a role to play in stopping the destruction caused by the floating pennywort – and the release of the South American weevil will bolster our efforts to eradicate this pest from our waterways once and for all.”

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The outings took place during the winter, others are planned for this summer. Since 2011, the Center for Agriculture and Bioscience International (CABI), with funding from Defra, has been investigating the potential use of a biological control agent against floating pennywort. They found that Elongated Listronotus were effective in removing it when they laid eggs and ate the plant. The larvae also eat the stems, reducing its ability to grow.

Djamila Djeddour, Chief Scientist at CABI, said: “After years of extensive research into the biological control potential of the floating pennywort, we are delighted and delighted to have released the weevil into the wild. Field studies by CABI scientists and collaborators in South America revealed this weevil to be the most promising agent and after thorough screening at CABI’s UK quarantine facility, it was confirmed to be highly specialized, feeding and growing only on this noxious weed.

“Further releases will begin later this year, supported by a range of sponsors, and the impact, establishment and spread of the weevil will be closely monitored.”