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Axis of Weevil comes to aid of Somerset canal

An army of 2mm-long weevils will be dropped into the Bridgwater & Taunton Canal in Somerset on Friday 26 July in our continuing battle against a problematic North American water weed.

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Azolla might look attractive, but it’s actually a serious threat to water wildlife across the country.
Richard Haine

We're going to release the creatures into the water at Maunsel so they can eat the invading Water Fern (Azolla filiculoides).

Azolla is a voracious grower and can multiply rapidly, covering the surface of a waterway with thick mats in a matter of weeks. This reduces light and oxygen levels in the water, killing fish and other wildlife, as well as affecting how boaters and anglers can use the canal.

Individually the weevils (Stenopelmus rufinasus) consume a relatively small amount of Azolla, however they breed to produce very large populations which as a community will feed extensively, until sections of Azolla start to die and sink, where it is further broken down by other feeders. Given time to reproduce and spread throughout a mat of Azolla, the weevil is capable of clearing entire lakes or canals within a matter of weeks.

Pre-emptive strike

Richard Haine, environmental scientist at the Canal & River Trust, explains: “Azolla might look attractive, but it's actually a serious threat to water wildlife across the country. With the warmer weather there's a danger that it can completely take over sections of the canal, so the weevils are our pre-emptive strike.

“The weevils breed really quickly and only eat Azolla, so should be extremely effective. We'll monitor their progress, but we back them to do the job.

“The Bridgwater & Taunton Canal is a great place to visit at this time of year, excellent for boaters, walkers, families and people with an interest in wildlife – I encourage anyone in this part of Somerset to take a look for themselves.”

Each year we spend a huge amount of time clearing species of aquatic weed from the nation's canals, rivers, reservoirs and lakes. Many of these invasive weeds are freely available to buy as ornamental water plants in garden centres across Britain.

Last Edited: 24 July 2013

photo of a location on the canals
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