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Monday, October 18, 1999 Published at 13:04 GMT 14:04 UK


Beetles could battle super-weed

Biological "predators" could be imported into Britain to tackle a concrete-cracking super-weed which is spreading across the country.

Japanese knotweed has become the most invasive weed in Britain since it was brought here as an ornamental plant last century. The knotweed has also caused problems in parts of Europe and the US.

The virtually indestructible menace can grow to nearly four metres (12 feet) in just 12 weeks and millions of pounds a year are being spent in a vain battle to control it.

Now £400,000 is being sought to research the use in UK of a tiny Japanese beetle and a rust fungus which attack the weed in its native country, where it is not a problem.

In UK the weed has no natural predator, and Environment Agency biologist Trevor Renals warned: "If we leave it another 100 years we could see hundreds of thousands of acres smothered."

"It would be fighting nature with nature, and it is our only hope," said Mr Renals. He added the action would not eradicate the plant, but control it.

Careful checks

The bio-control proposal will be outlined before a high-level conference being set up by CAB International, an inter-governmental biological research organisation, in Ascot, Berkshire, next month.

CABI scientist Dick Shaw, who has been working on bio-control for over a decade, said three years of research would be needed to ensure imported controls did not attack any other UK plants.

Some past attempts at bio-control have gone wrong. The cane toad was introduced to Australia in the 1930s to eradicate the cane beetle, but, having few natural enemies, the toad itself has now become a serious pest in Australia.

The decision about whether a biological control would eventually be used lay with the UK Department of Environment, said Mr Shaw.

Persistent plant

The knotweed blackspots in UK are south Wales and the South West, where the plant has taken hold on sand dunes, forests and river banks, choking native species.

Before it can be developed, land on which the concrete-piercing plant is found has to be excavated to a depth of 4.5 metres (15 feet), to ensure no trace of root remains.

In the past flailing was used in a bid to control the plant - but the tiny fragments just sprouted into new weeds.

Photos courtesy of US Nature Conservancy.

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