Weed-munching weevils released to clear 'harmful' water fern

Image source, Dave Bootell

Image caption, The weevils have the capacity to clear rivers "within weeks", the Canal and River Trust said

Thousands of weed-munching weevils have been released into a Lincolnshire river to eat away at water fern which is posing a risk to fish and other wildlife.

The fast-growing Azolla weed is mixed in with duckweed on stretches of the River Witham in Boston and is up to 10cm (4in) thick in places.

The non-native plant is also causing issues for boat owners as it can become stuck in their engines.

A Canal and River Trust spokesman said weevils are capable of eating away at large swathes of the greenery in "a matter of weeks".

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Video caption, The fast-growing water fern poses a risk to wildlife in Boston's River Witham.

A spokesman for the trust said: "As navigation authority for the river, we鈥檝e been meeting with boaters, trip boats and marina operators in the area to listen to their concerns and put plans in place to improve the situation for them.

"We invest around 拢80,000 each year managing weed on the River Witham but this year, in recognition of the issues boaters and others that use the river are having, we鈥檙e going even further to tackle the problem.

"We鈥檝e added an extra weed boat on the river which is helping us to clear around 100 tonnes of weed each day.

"We鈥檝e also been using Boston Lock to help flush the weed along the river each day and have even added 3,000 weed munching weevils to tackle the non-native Azolla water fern."

Image source, Dave Bootell

Image caption, The river is carpeted in a mixture of Azolla water fern and duck weed

Boat owner Dave Bootell comes from Bedford each summer to spend time on the River Witham. He said in 30 years of sailing he had never seen so much coverage.

"Over the last 15-20 years, rivers have got cleaner and cleaner and you can see the fish stocks and the wildlife are getting stronger in the area," he said.

"I think because the rivers are so clean there is a build up of duck weed and plant life in the area.

"It builds up in the lock area and it gets deeper and deeper. The first thing we do is turn the engine on and it clogs it up."

The Canal and Rivers Trust said the duckweed is unusually bad this year.

The spokesman added the weevils only ate Azolla, and would not harm any other wildlife in the river.

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