Why Wales is perfect spot
THE geographical make-up of Wales makes it an ideal spot for Japanese knotweed to grow, an expert has said.
Swansea is one of the worst affected parts of the UK, with the total biomass of the plant estimated to be more than 62,000 tonnes in the city.
Dick Shaw is a project manger for a not-for-profit scientific research organisation, the Commonwealth Agricultural Bureaux International (Cabi).
Three years ago the group released the psyllid insect Aphalara — a natural predator of the plant — in a number of pilot areas, including Wales in a bid to tackle the problem.
He said: "The first part of the country it was found in was in Maesteg in 1835 and Swansea has one of the largest problems of it.
"It was a very valuable plant which was found on volcanic soil in Japan.
"In Japan it is a normal member of the flora. We released the insect into three sites in 2010 and another eight sites in 2011 and it will take another five to 10 years before we see any impact.
"The plant settles where there is a disturbance.
"Obviously in South Wales it has had an awful lot of disturbance through mining.
"The fact it found itself on a slag heap in Maesteg would have been a home from home for it.
"There has been quite a lot of knee-jerk reaction to it, if it is 130 foot away at the bottom of your garden then it is not going to threaten your property, and I think those concerns will settle down eventually.
"It is used to being in the most inhospitable habitats."