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Issued jointly by the Wey & Arun Canal Trust and Arun and Rother Connections

TINY beetles have halted an outbreak of weed which was choking part of a historic waterway.

The two millimetre-long North American weevils nibbled away at a carpet of vegetation on the Wey & Arun Canal, clearing the non-native water fern in just a few weeks.

Twelve thousand weevils were released into the waterway at Tickner's Heath, Dunsfold, in July, to combat Azolla filiculoides. This floating fern is considered one of the most invasive plants in the country.

"The exercise has had a remarkable impact on the water fern", said Ian Burton, the Wey & Arun Trust's conservation adviser. "The weevils speedily removed most of the water fern and have had a comprehensive impact. There is now no sign of the weed."

The project was a partnership between the Canal Trust, the Heritage Lottery funded Arun and Rother Connections (ARC) and the CABI (Centre for Agriculture and Biosciences International), which supplied the weevils.

ARC works with local organisations to help ensure wildlife can flourish in a thriving river system. As part of a wider programme of work to tackle a number of priority invasive species across the whole catchment area, project staff identified the invasive plant and provided the funding to purchase the weevils.

All known infestations of this invasive plant have now been removed from the river catchment. Wey & Arun Canal Trust will continue to monitor its waterway to ensure that the plants do not return in the spring.

"We acted to try and clear the weed because it had formed a thick mat on the surface of the water, blocking out the light and threatening the aquatic flora and fauna," Mr Burton added. "The canal appeared to be solid ground."

"Floating water fern multiplies rapidly and its area can double in a few days. We didn't want it spreading to neighbouring properties and other parts of the canal.

"We are delighted with the work of the little insects. There are no organisms native to the UK that can combat Azolla, but research has shown the weevils to be one of the plant's main natural enemies."

Individually, the weevils consume a small amount of Azolla, but they breed to produce large populations which feed extensively on the weed. Across the UK, entire infected lakes and canals have been cleared using this form of biological control.

Azolla was introduced into the UK from the Americas in around 1840 as an ornamental garden aquatic. Some North American weevils also arrived with the imported ferns, and the insect species is now considered naturalised.

They pose no threat to UK ecosystems, unlike the fern itself, which soon escaped into the wider environment, where it now causes considerable problems on ponds, lakes and waterways.

The initiative at Tickner's Heath is line with the Wey & Arun Canal Trust's policy of controlling and eradicating invasive species, including Himalayan balsam, giant hogweed and Japanese knotweed, on land that it has responsibility for.

Pictures at

Editor's notes:

For more information on this press release, or to request other supporting photographs, contact Wey & Arun Canal Trust fundraising, press and public relations officer Rob Searle.

Telephone 01276 857914

Mobile 07913 416435


1. Wey & Arun Canal Trust

For general information on the work of the Trust, please telephone our Northern Office on 01483 505566, or visit

2. The RSPB is the country's largest nature conservation charity, inspiring everyone to give nature a home. Together with our partners, we protect threatened birds and wildlife so our towns, coast and countryside will teem with life once again. We play a leading role in BirdLife International, a worldwide partnership of nature conservation organisations.

2. Arun and Rother Connections (ARC) is a partnership project between the RSPB, Environment Agency, Sussex Wildlife Trust, South Downs National Park Authority, Natural England, West Sussex County Council and the Arun and Rother Rivers Trust. The RSPB is the lead partner, holding overall responsibility for successful delivery of the project.

The ARC Partnership is very grateful to the Heritage Lottery Fund for supporting the project.

The ARC project aims are to:

• Promote a rich and thriving river system where wildlife flourishes and where people value and enjoy the landscape, natural and cultural heritage

• Work with landowners to protect, restore and reconnect wildlife habitats

• Improve water quality and eliminate non-native invasive species

• Better connect the community to the catchment, through access improvements, engagement opportunities and interpretation of the natural and cultural heritage of the project area.

For more see or follow #ARCproject on twitter

3. The Heritage Lottery Fund. Using money raised through the National Lottery, the Heritage Lottery Fund (HLF) aims to make a lasting difference for heritage, people and communities across the UK and help build a resilient heritage economy. From museums, parks and historic places to archaeology, natural environment and cultural traditions, we invest in every part of our diverse heritage. HLF has supported almost 35,000 projects with more than £5.5bn across the UK.