Specialist weevils deployed in Yorkshire waterways to tackle invasive plant

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

The swimming navel beetles were introduced on the Aire and Calder Navigation and one of the tributaries of the River Holme, in collaboration with Yorkshire Water, the Center for Agriculture and Bioscience International (CABI), Leeds Council, River Holme Connections and a private landowner.

The beetles, which have evolved to only feed and develop on floating pennywort (Hydrocotyle ranunculoide), target the plant where it clogs the waterways.

Native to Central and South America, floating pennywort was brought to Britain as a pond ornamental plant in the 1980s but escaped to natural habitats where it can grow up to 20cm per day.


Floating pennywort clogs a spot on the Aire and Calder Navigation (CABI /PA)

It forms dense vegetative mats on watercourses, reduces oxygen availability for fish and aquatic insects, clogs drainage systems, crowds out native aquatic plants and poses a risk to livestock, dogs and human health, the team behind the publication said.

After a decade of safety and efficacy testing by CABI, South American weevils were approved for release as a natural pest control for the invasive plant, avoiding the need for mechanical or chemical intervention.

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

dr Steph Bradbeer, Invasive Species and Biosecurity Advisor at Yorkshire Water, said: “Invasive alien species pose a very real risk to the environment and wildlife of Yorkshire.


Weevil on Floating Pennywort (CABI/PA)

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

“Floating pennywort, if left uncontrolled, can cause significant problems in slow-moving watercourses and impingement drainage systems.

“We hope that releasing these specialized weevils will provide a way to counter them without mechanical or chemical intervention.”

Djami Djeddour, senior project scientist at CABI, said: “These weevil releases are the culmination of over a decade of collaboration with South American scientists and extensive safety and efficacy testing at our quarantine facilities, so it’s exciting to finally get them into the wild.”

The weevils are closely monitored, carefully monitoring their impact on the spread of the floating pennywort.

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

https://www.belfasttelegraph.co.uk/news/uk/specialist-weevils-deployed-in-yorkshire-waterways-to-tackle-invasive-plant-42145177.html Specialist weevils deployed in Yorkshire waterways to tackle invasive plant


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