Bio-control solution for Japanese knotweed

Japanese knotweed, the bane of all gardeners, was first introduced to the UK as an ornamental plant, prized for its beautiful white flowers.

However, the fast-growing plant quickly spread out of control, suffocating surrounding vegetation and threatening local habitats.

Knotweed can grow up to 4 metres tall, and is so strong that it can break through paving stones and tarmac.

It is one of the few plants in Europe that is seen as such a pest that there is legislation banning its cultivation, movement and planting.

In Japan, knotweed is common but does not grow out of control.

The estimated cost of removing knotweed from the UK runs into billions of pounds.

However, researchers at Cabi, a non-profit agricultural organisation, have come up with a low cost ‘bio-control’ solution.

Bio-control is a pest control method whereby an unwanted species is kept under control by introducing its natural enemy.

Scientists at Cabi have identified knotweed’s natural predators in Japan, and have submitted plans to the UK government to have these species introduced into the UK.

After finding 186 species of insect and 40 types of fungi that feed on knotweed, the scientists narrowed down the shortlist by working out which bugs and fungi fed only on knotweed and not on other plants native to Britain such as wheat and apples.

The research found two bugs suitable for introduction in the UK, a sap-sucking psyllid insect and a fungus that rots the leaves of knotweed.

If the plans to introduce the knotweed eating bug and fungi are given the go-ahead, it will be the first time ever that bio-control has been permitted in Europe.

Dick Shaw, who led Cabi’s research, said that compared to other method of removing knotweed, using bio-control would be ’significantly less costly’.

The plans will first be reviewed by the Department for Environment, Food and Rural Affairs (DEFRA) before submitted for public consultation.