Japanese 'vampire' bugs to curb UK weed

It damages buildings, smothers train tracks and clogs up riverbanks and habitats, costing millions of pounds each year to control. In its native country, knotweed is kept in check by insects that feed on it, but none of these exist in the UK.

Now, that could be about to change with the possibility of a tiny predator being released into the wild within a year.

Scientists have been researching the 0.5mm-long nymphs of the psyllid, which they brought back from Japan.

They act like vampires, sucking the sap from the knotweed and hampering its ability to spread.

Dr Dick Shaw, the principal investigator at environmental research body CABI Europe, who led the research, said the weed had the "biodiversity value of concrete". He added: "The trouble is, this weed has lost its natural enemies."

The challenge was to find an insect that could keep Japanese knotweed under control, but that did not itself cause havoc to Britain's native species.

Following strict quarantine measures to make sure that none of the bugs escaped, Dr Shaw and his team have spent the past four years studying the insects to find out how they behave around species native to the UK.

He thinks that the risk of the psyllids themselves disrupting Britain's ecosystem is low because the bugs have evolved over centuries to feed specifically on Japanese knotweed.

"It has taken millennia to become a specialist on knotweed, so the chances of it changing to something else is very unlikely," Dr Shaw said.

He said that the nymphs would not kill the knotweed, but just control its spread. "If it killed all the knotweed, it would die out itself," he explained. "So you usually end up with an equilibrium."

If the Department for the Environment, Food and Rural Affairs (Defra) decides to release the bug, it would be the first time a foreign insect has been introduced to the UK to tackle an invasive weed.

The 440,000 research has been part-funded by Network Rail, which is desperate to find a way to control Japanese knot-weed on its tracks.

The weed was brought into the UK by the Victorians as an ornamental plant, unaware that it would spread across the country.

Insects will combat second invader

BUGS could also be used to control another invasive weed in Scotland – Himalayan balsam.

Scientists at CABI Europe, a not-for-profit research organisation, will next week go to India to find insects that act as natural enemies to the plant.

They will spend a week in the Himalayas collecting bugs found on the weed in its native environment.

A selection of insects will be brought back to the UK and a lengthy research process will begin to find out how they interact with our native species.

Like Japanese knotweed, Himalayan balsam is an invasive plant that has spread out of control and has no natural predators in the UK.

Each plant produces about 2,500 seeds and exploding seed cases propel them up to five metres from the parent plant.

It is such a problem that the Scottish Government is helping to fund CABI's research, along with the Department for Environment, Food and Rural Affairs (Defra) and the Environment Agency.

Himalayan balsam was introduced to Britain in 1839 as a garden plant. Within a few decades it had escaped into the wild. It causes erosion of riverbanks as it leaves bare patches of soil when it dies in the autumn which are then easily washed away by rain.

Defra will assess the research, and there will be a public consultation before ministers decide whether to let foreign insects into the wild in the UK.