Munching Weevils tackle Water Fern

An army of 2mm- long weevils have been dropped into the Manchester, Bolton & Bury Canal in Manchester to help the Canal & River Trust battle against a problematic water fern.

The Weevils were released into the water near Elton Reservoir in Radcliffe. The aim is for them to eat the invading water fern (Azolla filliculoides) which can be problematic if left in the canal network due to its energetic growth. If left unchecked this tiny fern can cover a large stretch of canal in a matter of weeks which reduces light and oxygen levels within the water killing fish and other wildlife. The dense mat of growth also makes it very difficult to navigate through.

The weevils breed extremely rapidly and only eat water fern so are very effective in destroying the plant without causing further damage to other species.

Becki Anderson, Senior Ecologist at the Canal & River Trust said: “Water Fern (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 it can completely take over sections of the canal, so the weevils are our pre-emptive strike”

The Canal and River Trust have used weevils in several canals over the last few years to tackle the problem of water fern, they’re proving to be a very effective method of clearing this invasive species. In 2012, they were used extensively in the East Midlands area, and the Azolla water fern hasn’t been a problem since. The Bridgwater & Taunton Canal was also treated last year, and so far this year, it hasn’t been spotted. This year, weevils are also being used on the Gloucester & Sharpness Canal, and the Huddersfield Broad Canal.

Each year the Trust spends a huge amount of time clearing species of aquatic weed from the nation’s canals, rivers and reservoirs. Many of these invasive weeds are freely available to buy as ornamental water plants in garden centres across Britain. Whilst lovely to look at in a garden pond, it is important these plants are disposed of properly when no longer wanted, and not released into the wild.

Last date edited: 20 August 2014

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The Canal & River Trust has top team of committed experts and enthusiasts, who help to protect our waterway environment and improve it for both people and nature. Follow this blog to find out more about the hugely varied work they carry out.

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