‘Biggest risk to property market’: Manchester experts tackle knotweed pandemic costing UK £166m a year

Britain’s Japanese knotweed pandemic, which costs the economy over £166million per year, is set to be tackled by a recently-launched Greater Manchester company.

The National Knotweed Survey aims to raise awareness of the largely-unreported issue by creating a searchable map that shows the presence of knotweed across the British Isles.

The founders will do this using years of academic research, historical and treatment records and high-tech aerial imaging to make information available to interested parties.

DATA SPECIALIST: Will Sillar from Wilmslow warns of knotweed threat

Company founder Will Sillar, a data specialist from Wilmslow, said: “Japanese knotweed is the biggest unquantified and unmanaged risk in the UK property industry.

“There is estimated to be at least one infestation of the plant in every ten kilometres-squared in the UK.”

Japanese knotweed was brought to the UK during the Victorian era as an ornamental garden plant, but it has since proven to be highly disruptive.

The weed, which can grow at a rate of up to 40 millimetres per day, is an invasive plant that can break through tarmac, concrete and structural work.

Its presence can devalue land, sometimes rendering a property completely worthless.

In 2014, Mortgage Solutions carried out a survey which found that 90% of mortgage brokers admitted to having deals fall through because of knotweed.

The treatment of Japanese knotweed during the development of the 2012 London Olympic Stadium cost a reported £70million – almost a quarter of the cost of the whole project had to be spent again to remove knotweed.

However, those at the National Knotweed Survey fear that the problem may be even more costly than is known due to the fact that the issues are rarely spoken about.

Mr Sillar emphasized the enormity of the problem.

He said: “Mortgage lenders, estate agents, solicitors, insurers and indeed anybody buying or selling a property, are often in the dark with regard to the knotweed problem.

“Questions of how to spot it, what to do, and whose responsibility it is, have led to hundreds of millions of pounds’ worth of business falling through every year.”

Alongside the searchable map, the National Knotweed Survey aims to standardize the way knotweed is reported and remedied in order to ‘bring some transparency to the surveying business’ and ensure that knotweed issues are noticed and tackled effectively.

Recognizing the serious threat posed by knotweed, Manchester City Council recently launched an initiative to do eradicate infestations in public places across the city.

The £685,000 project will be funded by the clean city fund, which comes from the city council’s shareholding in Manchester Airports Group.

The project will pay for specialist herbicide treatments which will get rid of the plants over the next three years.

Due to the status of Japanese knotweed as a non-native invasive species, legislation was introduced in 2014 that allows councils and police to order an affected party top prevent the weed spreading.

A breach of this order can lead to the person who failed to control the growth served with an Anti-social Behavior Order, an on-the-spot fine of £100, or facing prosecution with a maximum fine of £2,500.

This means that knotweed poses a threat to anybody in possession of an infected piece of land, however small the infestation is.

Recently, a church in the Greater Manchester town of Ramsbottom had to foot the bill for the remediation of a knotweed problem.

Steve Gaskell, pastor of Ramsbottom Pentecostal Church, said: “We were looking at extending the building onto this land and it’s only when we got people in to look at extending it that we discovered the Knotweed.

“We were then told we were not allowed to extend the building until the Knotweed was dealt with, so we could do no further development until that was sorted out.

“Forgetting my time and having to meet people and ring up, it’s cost us near £5,000. Just because of some Knotweed in the land.”

Despite costs such as these, it is essential that the growth of Japanese knotweed is kept under control.

The National Knotweed Survey has advised those who find knotweed on their land should either arrange to have the plant injected with specially devised herbicide, or have the plant, roots and any contaminated surrounding soil excavated.

Once excavated, the plant, roots and soil can either be disposed of at a licensed landfill site or onsite in a special underground interwoven, sealed, membrane capsule.

It has been stressed that the plant should not be dumped outside of a legally agreed site, burned or simply ignored.

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