Bug could offer solution to concrete-cracking weed

It can grow more than a metre a month, can force its way through tarmac and concrete, and is costing the UK millions, but scientists believe they have found a natural way to tackle Japanese knotweed.

Researchers at the Centre for Agricultural Bioscience International (CABI) say a bug which feeds on the plant in its native Japan could safely be introduced in the UK.

The sap-sucking psyllid was one of more than 200 natural control agents tested to ensure it would not affect native plant species.

Japanese knotweed has spread throughout the UK since it was introduced by the Victorians as an ornamental plant, and is particularly a problem in parts of Cornwall and Wales. A Defra working group estimates it would cost £1.56bn to control it using traditional methods.

“Almost all of the non-native invasive species introduced to the UK have arrived without the suite of natural enemies which keep them in check in their native range,” Dr Dick Shaw, principal investigator at CABI, said.

“What scientists call classical biological control aims at redressing this imbalance by re-associating the plant with one or more of its co-evolved natural enemies, but only after extensive safety testing under quarantine conditions.”

Since 2000, CABI has been working on ways to stop the spread of Japanese knotweed in a project funded a number of agencies, including Defra, the Welsh Assembly Government, and Cornwall County Council.

Of the hundreds of insects and pathogens tested, only the sap-sucking psyllid and a leafspot fungus were found to be predators solely of Japanese knotweed.

Work is further ahead on the psyllid, which has a less complicated lifecycle, and the scientists say it could be introduced as early as next summer.

It would take between five and ten years before the results would be seen, although the introduction of the insect would only control knotweed, not eradicate it altogether, they added.

Kate Martin

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