In an attempt to control the invasive mussel, Dr. David Aldridge and his team from the Zoology Department, University of Cambridge, have developed an environmentally friendly sugar coated pill with a lethal dose of potassium chloride.

The zebra mussel (named for its striped shell) blocks intake pipes and filter screens, bringing power plants and waterworks to a standstill. The clam also has devastating impacts on wildlife by killing some species and by changing the nature of lakes and rivers so that native species can no longer survive.

The annual cost of zebra mussels in North America is estimated to be an incredible $3bn, and Britain is rapidly catching up. Zebra mussels have been spreading through Britain's rivers and lakes since 2000, and the situation is being monitored by Dr. David Aldridge and his team.

Dr. Aldridge said: "We are really concerned. Zebra mussels are appearing everywhere, and are encrusting just about every solid surface available in rivers such as the Thames and Great Ouse. What's more, they're smothering and killing some of our native mussels."

Zebra mussels can be controlled by chlorine, but the chemical has environmental drawbacks. Furthermore, mussels can sense chlorine and other toxic substances and limit their exposure to the chemicals by closing their valves for as long as three weeks. However, Aldridge and his team report in the journal Environmental Science and Technology that they may have found a solution to the problem.

They realized they needed to devise a Trojan horse technique to get a toxic compound past the mussels' defences. The researchers packed potassium chloride, which is deadly to zebra mussels but doesn't affect most other organisms, into microscopic particles made of fats. The mussels transfer the particles, or "BioBullets," along their gills and into their mouths. The particles rapidly dissolve in the animals' stomachs, releasing a lethal dose of potassium chloride. BioBullets could be loaded with other cargo to control other pests or to feed useful species.