Weevils go to war on weeds in Huddersfield canal

Sep 11 2010 Huddersfield Daily Examiner

MEET Willy the weevil – the tough guy of the canal.

This tiny creature – properly known as Stenopelmus rufinasus – measuring just 2mm, is waging war on a North American invader in Huddersfield Broad Canal.

And waterways chiefs are confident Willy and his mates can see off the invader, which if unchecked could choke the life out of the canal.

British Waterways has recruited the weevils to fight the water fern Azolla filiculoides.

The creatures were released into the Huddersfield Broad Canal at Cooper Bridge in order to eat the invader weed which originated in North America.

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.

Individually the weevils consume a relatively small amount of Azolla. But they breed rapidly to produce very large populations which as a whole can be incredibly damaging, feeding extensively on the Azolla mat until sections start to die and sink where it is further broken down by microbes and other feeders.

The tough-guy weevils can clear an entire lake or canal within three months.

Jonathan Hart-Woods, British Waterways environment manager, said: “Water fern was first introduced to the UK by the Victorians as an ornamental plant for ponds.

“Despite looking attractive, 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.