Four thousand hungry weevils have been released into a Huddersfield canal in a bid to destroy an invading water fern.
The Canal and River Trust, the charity that cares for the nation’s historic waterways, has released the 2mm-long weed weevils into the Huddersfield Broad Canal near Colnebridge so they can eat the Water Fern (Azolla filliculoides).
Azolla is a voracious grower and, if left unchecked, could cover the surface of the canal with a thick mat, reducing light and oxygen levels in the water and causing problems for boats and anglers.
The weevils are an effective natural means of tackling Azolla and are at their most active at this time of year. They breed quickly so collectively they can eat their way through a very large mass of the water fern in just a few weeks.
And the weevils are known to feed exclusively on Azolla and don’t cause damage to other native species so are ideal for tackling the problem.
Trust ecologist Phillippa Baron said: “Azolla might look attractive but it’s actually a serious threat to the health of the canal so it’s important that we step in and take action.
“Introducing thousands of weed-munching weevils may seem like an extreme course of action but it’s been tried elsewhere and had great results so we’re looking forward to seeing them do their stuff on the Broad Canal.”
Azolla originates from the Americas but was introduced into the UK in the 19th century as an ornamental plant for garden ponds. The weed soon escaped and continues to cause problems on canals, rivers and lakes.