Specialist weevils deployed in Yorkshire waterways to combat invasive plants

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Specialist weevils from South America have been introduced to two sites in West Yorkshire to control an invasive non-native plant that is choking waterways.

Floating pennywort weevils have been introduced to the Aire and Calder Navigation and one of the tributaries of the River Holme, through a collaboration between Yorkshire Water, the Center for Agriculture and Bioscience International (CABI), Leeds Council, River Holme Connections and a private body. owners.

Stink bugs, which have evolved to feed and thrive only on the floating pennywort (hydrocotyl ranunculoid), will target the plant where it clogs waterways.

Water pennywort is native to Central and South America and was brought to the UK in the 1980s as an ornamental pond plant, but escaped into natural habitats where it can grow up to 20 cm per day.

It forms dense vegetative mats on waterways, reducing oxygen availability to fish and aquatic insects, smothers drainage systems, outcompete native aquatic plants, and pose a risk to livestock, dogs, and wildlife. human health, the team behind the statement said.

After a decade of safety and efficacy testing by CABI, South American weevils have been approved for release as a natural pest control for the invading plant, obviating the need for mechanical or chemical interference.

The adult weevils feed on the leaves of the floating pennywort and the females lay eggs in their stems, where the larvae then eat the stems of the plant, reducing its ability to grow and spread further.

Dr Steph Bradbeer, Invasive Species and Biosecurity Advisor at Yorkshire Water, said: “Invasive non-native species pose a very real risk to the environment and wildlife in Yorkshire.

“They can also impact our ability to treat and distribute water to homes and discharge wastewater safely into the environment.

“Water pennywort, if left unchecked, can cause significant problems in slow flowing waterways and impact drainage systems.

“We hope the release of these specialized weevils will provide a way to tackle them without requiring mechanical or chemical intervention.”

Djami Djeddour, Senior Project Scientist at CABI, said: “These weevil releases are the culmination of more than a decade of collaboration with South American scientists and extensive safety and efficacy testing at our facilities. quarantine, so it’s exciting to finally bring them out into the wild.”

Weevils will be closely monitored, and their impact on the spread of water pennywort carefully monitored.

It is hoped that they will help improve local wildlife and water quality, reduce the plant’s impact on flood defenses and control the spread of water pennywort in rivers.