Japanese knotweed cannot be cured major study which tried 19 methods finds

Japanese knotweed cannot be cured, a major study which tried 19 methods over three years has found. Researchers from Swansea University conducted the world’s biggest ever study into eradicating the invasive weed at two sites in Taff’s Well, near Cardiff, and in Swansea.But despite using various chemical solutions, physical projects and a mixture of the two, the scientists found no definite ways of killing the plant completely using current methods.Professor Dan Eastwood from the project said: “Basically, we’re discovering how best to tackle invasive plants in real world conditions, informed by evidence of what actually works. We began focusing on knotweed at a time when there was a great deal of hysteria surrounding it.”At the time, most information for people affected by the plant was largely based on anecdote. This led to the prospect of unscrupulous companies offering expensive and ineffective treatment solutions.”It was incredible to us that there was no long-term, large-scale field trial analysis of the treatment methods used to control Japanese knotweed.” Professor Dan Jones said gardening companies who claim to be able to eradicate the plant were not fully accurate.He said: “Off the back of the first three years of data we’ve found that eradication is not possible. Hopefully over the longer term we may move towards that by using new chemicals we’re looking at. “But it’s not a question of eradication, it’s a question of sustained control and management and well informed control and management.”Claims made by companies, stating that they could eradicate Japanese knotweed using herbicides in short spaces of time have now been proven to be false, based on our experiments.”Furthermore, we have shown that applying the wrong herbicides at the wrong time of the year leads to greater herbicide use and environmental impacts.”Dr Jones said the best chemical to control the knotweed was glyphosate – but the herbicide is feared to pose a risk to other wildlife too. Dr Jones said: “There’s a range of issues in terms of risk and hazard. There’s a political issue around glyphosate as well.”What we’ve done is work with the biology of the plant to minimise the amount of herbicide we’re using over a treatment life cycle.”Although we’re using quite a contentious herbicide in that respect, we are using far less of that herbicide than you would use for other products that don’t work on Japanese knotweed.”Househunters looking at homes in areas dense with Japanese knotweed can often struggle to secure mortgages – over fears the roots could cause structural difficulties to buildings.Chartered surveyor David Gregson, who provides specialist advice on the issue, said: “The main problem is mortgage lenders are very reluctant to lend on properties where knotweed is present and obviously that means in turn people can’t sell their properties and it might sometimes be because knotweed is present in the next door garden. “A typical situation is a couple wanting to get divorced. They’ve got a lot of knotweed in their garden, they both want to move on with their lives and they’ve got a house they can’t sell.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily  Front Page newsletter and new  audio briefings.

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