Popular flea treatments used on dogs could be harming environmentally sensitive ponds and streams in the New Forest, a study has found.

Researchers discovered that one of the common insecticides used in the treatments, a chemical called imidacloprid, was present at four locations where dogs are known to regularly enter the water.

They include Dibden Bottom, where levels of imidacloprid were almost twice the internationally agreed toxicity threshold for aquatic invertebrates.

Samples collected from Cadmans Pool, Green Pond, and Janesmoor Pond were also found to contain imidacloprid.

Daily Echo: A popular flea treatment used on dogs could be harming environmentally sensitive ponds and streams in the New ForestA popular flea treatment used on dogs could be harming environmentally sensitive ponds and streams in the New Forest (Image: Peter Miller)

The highly toxic chemical has been banned as an agricultural insecticide but is still used in flea treatments applied to the back of a pet's neck.

Previous studies have shown that prolonged exposure can harm insects, including dragonfly, damselfly, and mayfly larvae. They are an important part of the aquatic ecosystem, providing food for fish, birds, and bats.

The survey work was carried out by Wild New Forest and Freshwater Habitats Trust.

Prof Russell Wynn, of Wild New Forest, said: "We suspect that most dog walkers will be unaware of the potential impacts of allowing their dog to enter water in the New Forest.

"We hope that by collecting and openly sharing these data we can raise awareness among the community and start a positive discussion about less harmful alternatives."

Daily Echo: A popular flea treatment used on dogs could be harming environmentally sensitive ponds and streams in the New ForestA popular flea treatment used on dogs could be harming environmentally sensitive ponds and streams in the New Forest (Image: Newsquest.)

Dr Naomi Ewald, of Freshwater Habitats Trust, added: "The New Forest is an Important Freshwater Landscape, where ponds and small headwater streams support some of the most diverse plant and animal communities to be found in the UK.

"These habitats also support our rarest freshwater species, which have disappeared from large swatches of the wider countryside.

"Keeping New Forest freshwater clean and free from polluting agricultural nutrients and urban chemicals is a priority if these species are to survive and thrive."

The survey team is working with New Forest Dog Owners' Group (NFDOG) and other organisations to help raise awareness of the issue and provide information about alternative, less harmful treatments.

They are also planning to alert vets in and around the Forest.

Heather Gould, chairman of NFDOG, said: "Vets are aware of the issue, and owners should discuss this before selecting which treatment to use. The same applies in pet stores of owners buy their treatment there."

Further sampling will take place in the summer, when more people will be using the Forest for recreational activities, including dog walking.