British Waterways declares axis of weevil in biological warfare

4 August 2010

British Waterways has enlisted the help of 2mm-long weevils in its battle against a particularly problematic North American water weed. The creatures are to be released into the Bridgwater & Taunton Canal at Maunsel Lock in Somerset in order to eat the invader weed - water fern (Azolla filiculoides).

Although individual water fern plants are only around 10mm long, they are voracious growers 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.

Robert Randall, British Waterways ecologist, explains: “Water fern was first introduced to the UK by the Victorians as an ornamental plant for ponds. Despite looking nice, this weed is actually a serious threat to waterway wildlife in the UK.

“As the warm weather continues, there’s a danger that it will take over completely, so introducing weevils to the canal acts as a natural pre-emptive strike in getting rid of this weed. 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. If we don’t act now there is a danger that birds may inadvertently transfer the weed to the the rest of the canal. Then it will be much harder to contain the spread.”

Last year, British Waterways had to spend more than £400,000 on clearing water fern (also known as fairy moss and floating water fern) and other aquatic weeds from the 2,200 mile network of canals, rivers, reservoirs and lakes that it cares for. Many of these invasive weeds are freely available to buy as ornamental water plants in garden centres across Britain.

Robert advises: “Garden ponds are generally great for wildlife, however, I urge anyone who is thinking of buying plants for their pond to consider the effect that certain, generally non-native, species can have on your local waterway wildlife. If you already have these plants in your garden and need to dispose of them, don’t put them down the drain or in the rubbish. Instead, compost, burn or bury them.”

ENDS

For more information and photographs contact:
Nayna Wood 020 7985 7263 / 07796191120 nayna.wood@britishwaterways.co.uk
Sarah Rudy 01908 302520 / 07788691219 sarah.rudy@britishwaterways.co.uk

Notes for editors
Invasive water plants include:

• Floating water fern/fairy moss (Azolla filiculoides)
• Floating pennywort (Hydrocotyle ranunculoides)
• Australian swamp stonecrop (Crassula helmsii)
• Parrot’s feather (Myriophyllum aquaticum)
• Water primrose (Ludwigia grandiflora)
• Curly waterweed (Lagarosiphon major)

Alternative oxygenators for ponds include:

• Spiked water milfoil (Myriophyllum spicatum)
• Rigid hornwort (Ceratophyllum demersum)
• Common water starwort (Callitriche stagnalis)

British Waterways cares for and maintains the nation's 2,200 mile network of canals and inland waterways, working in partnership with private companies, local authorities, voluntary groups and other government agencies to protect and enhance the waterways, and benefit the communities through which they run. www.britishwaterways.co.uk