Pictured: James Murphy, technician at Pestbusters injecting knotweed stems using a vehicle which sprays herbicide to help prevent the spread of knotweed

More areas of land are being contaminated with one of the most invasive and difficult to control menaces to land, warns a pest control expert.

Dave Nash, managing director of Birmingham based Pestbusters said despite Japanese knotweed being highlighted as hazardous waste there appeared to be a widespread ignorance to its destructive capabilities.

"We are seeing more and more land contaminated and there are many people who don't realize just what this weed can do," said Mr Nash, whose company are in Kings Norton.

"Most of the major lenders refuse mortgages now if Japanese Knotweed is anywhere in the vicinity, but despite this the public by and large remain unaware."

Mr Nash said that last year the weed, which was imported by the Victorians into the UK, cost the British economy hundreds of millions of pounds. It has no known predators in the UK, spreads rapidly and can grow through masonry.

He added: "In Asia there are insects that eat the plant keeping it under control, but here if it takes hold it can be a hard process. It is best, dare I say, to nip it in the bud."

Mr Nash said: " We are certainly receiving far more calls than we were a few years ago, but no where near enough from what we see on land driving around, to make sure we can stop contaminations from taking hold."

"As controlled waste it has to be burnt and as the roots bury so deep they can cause huge problems to buildings. The plant when mature in late summer has hollow canes, can grow three metres high and have creamy white small flowers."

Mr Nash added: "We are now using a new herbicide which we believe to be the be the best current method. We inject the stems but although effective it can be a difficult job for the pest control officer. Education for early preventative measures is clearly still the best way forward."