Photo shows an adult psyllid, a Japanese insect that will be introduced on a trial basis in Britain to tackle Japanese knotweed, a damaging super-weed which costs millions to tackle every year. (AFP)

LONDON (AFP) — A Japanese insect is to be introduced on a trial basis in Britain to tackle a damaging super-weed, the government said on Tuesday.

Japanese knotweed was originally used as an ornamental plant in gardens across Britain but has rapidly spread, costing over £150 million a year to control.

Agricultural and environmental research organization CABI claim the psyllid bug from Japan — or "jumping plant lice" — is a successful and natural way of controlling the weed.

"We have every reason to believe that this knotweed specialist can help limit impacts of this harmful invasive weed safely and sustainably," said Dick Shaw, lead researcher of the project.

The non-native bug will be released to a small number of sites across England this spring — the locations are being kept secret to prevent the trials being disrupted — and monitored to check progress.

Huw Irranca-Davies, a minister at the Department for Environment and Rural Affairs (Defra), said:

"This project is not only groundbreaking, it offers real hope that we can redress the balance.

"These tiny insects, which naturally prey on Japanese knotweed, will help free local authorities and industry from the huge cost of treating and killing this devastating plant."

The plant can grow up to a meter a month, causing damage to anything in its path such as buildings, roads and pavements.

CABI says it is sure the psyllid will only target Japanese knotweed and a few other similar non-native species, after testing it on 90 different British plant species over seven years.

Critics say this is not guaranteed and the bug could target other species once released. CABI says it has contingency plans in place just in case.

"There are isolated sites in the south of the country... so that we can monitor very closely and have a contingency plan in place, and then it'll be a wider scale release if it passes that test," Shaw told BBC radio.