Weevils are being used as a weapon against canal-threatening water ferns on a Somerset canal.
British Waterways is releasing the 2mm-long beetles into the Bridgwater and Taunton Canal to eat the North American fern.
Individual water fern plants are only around 10mm long, but they can multiply rapidly over the surface of a waterway with thick mats within weeks.
This reduces light and oxygen levels in the water, killing fish and wildlife.
British Waterways ecologist Robert Randall will be releasing the weevils at Maunsel Lock near Bridgwater.
He said: "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."
Mr Randall said the weevils breed extremely rapidly and only eat water fern so are very effective in destroying the plant, without causing damage to other species.
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 (3,219km) network of canals, rivers, reservoirs and lakes that it cares for.