Insect that fights Japanese knotweed to be released
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Science reporter, BBC News http://news. bbc.co.uk/ 2/hi/science/
nature/8555378. stm
A tiny Japanese insect that could help the fight against an aggressive
superweed has been given the go-ahead for a trial release in England.
Since Japanese knotweed was introduced to the UK it has rapidly
spread, and the plant currently costs over £150m a year to control and
clear.
But scientists say a natural predator in the weed's native home of
Japan could also help to control it here.
The insect will initially be released in a handful of sites this
spring.
This is the first time that biocontrol - the use of a "natural
predator" to control a pest - has been used in the EU to fight a weed.
Wildlife Minister Huw Irranca-Davies said: "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."
Alien invaders
Japanese knotweed was introduced to the UK by the Victorians as an
ornamental plant, but it soon escaped from gardens and began its
rampant spread throughout the UK.
It grows incredibly quickly - more than one metre a month - and
rapidly swamps any other vegetation in its path.
It is so hardy that it can burst through tarmac and concrete, causing
costly damage to pavements, roads and buildings.
But removal is difficult and expensive; new estimates suggest it costs
the UK economy £150m a year.
However, in Japan, the plant is common but does not rage out of
control like it does in the UK, thanks to the natural predators that
keep it in check.
Scientists at Cabi - a not-for-profit agricultural research
organisation - used this as their starting point to track down a
potential knotweed solution.
They looked at the superweed's natural predators - nearly 200 species
of plant-eating insects and about 40 species of fungi - with the aim
of finding one with an appetite for Japanese knotweed and little else.
After testing their candidates on 90 different UK plant species,
including plants closely related to Japanese knotweed such as
bindweeds and important crops and ornamental species, they discovered
a psyllid called Aphalara itadori was the best control agent.
The little insect feeds on the sap of the superweed, stunting its
growth.
Dr Dick Shaw, the lead researcher on the project from Cabi, told BBC
News: "Safety is our top priority. We are lucky that we do have an
extremely specific agent - it just eats invasive knotweeds."
This timelapse footage shows Japanese knotweed growing more than 1m-
tall (3ft) in just three weeks
Following peer review by the Advisory Committee on Releases to the
Environment and a public consultation, the UK government has now given
the go-ahead for release of Aphalara itadori, under licence, in
England.
The Welsh Assembly is expected to announce its decision on the psyllid
soon.
The insects will initially be released on a handful of sites.
These will be isolated and, in addition to as having the superweed
present, will also have UK species that are closely related to
Japanese knotweed planted there to check that the psyllid only targets
the invasive species.
Dr Shaw said: "In the early stages, a contingency plan is in place so
that should, in the unlikely event, any unintended consequences be
detected, we will be able to do something about it.
"Insecticide and herbicide treatment will be on standby for rapid
response."
If this phase is successful, the insect will be released at further
sites, where it will undergo an intensive monitoring programme over
the next five years.
Dr Shaw said: "On the localised sites, I would expect to see damaged
knotweed this season.
"However, biocontrol is a long-term strategy - it could take five to
10 years to have a real impact."
The government believes that if the plan is successful it will reduce
the costs to the building and engineering industries of clearing the
plant.
However, some critics say that it is impossible to be certain that the
Japanese insect will only target the superweed and could attack other
species once in the wild.