Despite the efforts of Government campaign Be Plant Wise, launched earlier in the year, invasive non-native species pond plants such as floating pennywort, parrot's feather and water fern are continuing to grow rapidly in Britain's canals and waterways.
Individual water fern plants are relatively small - around 10mm long - but grow voraciously and can cover the surface of a waterway with thick mats within a few weeks, reducing oxygen and light levels in the water and killing fish and other wildlife.
British Waterways ecologist Robert Randall explained: "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 rest of the canal. Then it will be much harder to contain the spread."
He added: "Anyone thinking of buying pond plants should consider the effect that certain, generally non-native, species can have on 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."
Last year, British Waterways spent more than £400,000 removing aquatic weeds from the 2,200-mile network under its care.