Japanese Knotweed: information and eradication

Below we have a guest post from Michael Alderwick, Director of Invasive Vegetation Management & Treatment Ltd. His website can be found at knotweed-uk.com

The post covers Japanese Knotweed and solutions for dealing with it:

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The Government has agreed to what is described as a handful of trials, isolated and under close scrutiny with “insecticide and herbicide treatment on standby for rapid response” for the release of Alphalara Itadori insect.

This psyllid will suck the sap out of the Japanese Knotweed leaf and stem with the hope that over a 5 – 10 year period we can reduce the spread. The estimated cost of controlling or eradicating the Japanese Knotweed plant by chemical treatment has been deemed unsustainable and unsuitable for a national eradication programme. The research into the introduction of a none native insect onto a non native plant has been conducted by a “not for profit research institute.” It is a somewhat subjective decision as to are you in favour or are you against, clearly something has to be done, we do not come from a neutral position as our business is eradication of Japanese Knotweed and like any other business we believe our service above others is the best.

Have you eve heard someone say “you cannot kill Japanese Knotweed” or “it takes years to kill Japanese Knotweed” well it is not true. You can kill Japanese Knotweed and further more it can be eradicated as quickly as 6 months with professional planning. This is absolutely guaranteed.

Japanese Knotweed (Fallopia Japonica) is the most pernicious invasive weed in the UK. It roots up to 3m deep, can regenerate from plant fragments, and is easily spread in soil, garden waste or even vehicle tyres. It is rapid growing and easily identifiable. Japanese Knotweed has hollow, upright, bamboo like stems, growing up to 3m in height. The large smooth edged leaves range from heart shaped (Japanese Knotweed) to huge “elephant ear” type leaves (Giant Knotweed).

The Seasons of Japanese Knotweed

In the Spring it emerges as a young red / purple shoot that turn green as they age. Some plants can leaf quite early but it can initially grow up to 50cm as a straight rod. In the summer the plant grows into bamboo like hallow stems up to 4cm in diameter and up to 3m in height with very lush, green leaves. In the autumn the plant becomes very attractive as it blooms with long clusters of small green and white flowers. In the winter the stems turn brittle and brown with the now brown and yellow leaves usually falling off at the first frost.

In a built up environment Japanese Knotweed shoots are able to push up through asphalt, damaging pavements, car parks and public utilities. Rhizomes have been recorded penetrating foundations, walls and land drainage.

Japanese Knotweed was introduced to the UK by the Victorians as an ornamental and fodder plant. Due to its root mass, it was used for both bank stabilisation of canals, road verges and railway embankments. The plant spreads from rhizome and stem materials with as little as 10mm length of 0.7g fresh weight of rhizome can give rise to new plants. The crown and the rhizomes act as a massive storage organ which allows massive rapid growth in the spring and is a big advantage for Knotweed over other indigenous plants.

It is an offense to knowingly spread Japanese Knotweed and in a built environment is usually conditioned as part of the planning process for action. Back in 2005 there was a published estimate of circa £1.6billion to completely eradicate knotweed from the UK, the figure is probably much higher now.

As a leading business for the eradication of Japanese Knotweed, we are aware of the demolition and construction industry requirements to successfully treat Knotweed at a rate that is compatible with programme constraints throughout the year, including the dormant winter period. The professionals involved with the built environment hold knowledge that there are a few market options to treat and kill Japanese Knotweed in a single growing season, including our own F.A.S.T (Foliage and Stem Treatment) System which is now established, and such herbicidal treatments are clearly the most economic to the end user.

The Government emphasis and intent to reduce carbon footprint has had a severe impact on the cost to remove the problem by way of excavation and transport to tip. The tax levied by HM Customs and Excise is now prohibitive and the ability to apply for contaminated landfill tax exemption has ceased. To offset this penalty, Japanese Knotweed was included in the 2009 Finance Bill for 150% tax relief against the cost of treatment only, but there are exceptions and not all sectors can realise the benefit. It is easy to understand the Government policy, we cannot indefinitely create massive landfill sites simply moving the problem from point A to point B. The number of landfill sites capable of receiving Japanese Knotweed is reducing and the distance to travel from source to tip involves unnecessary lorry movements, sometimes at excessive distances. Using Environment Agency guidelines, a single stand of Japanese Knotweed calculates out at up to 18 lorry transport movements.

The demolition and construction industries need to understand that forward thinking and planning is needed. In the majority of instances Japanese Knotweed is recognised at an early stage and it is now common to see it noted on intrusive site investigation reports as an integral part of the planning process.

The simple rules are that any development that permits a program for eradication in a full growing season can have the plants killed at a cost circa 10% of the cost to tip. Any development that requires immediate excavation and removal to tip will suffer severe and unnecessary financial penalty.

Is There an Alternative Solutions?

Industry is not slow to spot an opportunity and a few innovative ideas are now offered

* On site cell burial is available; in our view it is expensive, you need space and you need an area not designated for future development
* There are root barriers available which are designed to stop the spread and will eradicate the plant in the longer term.
* In the last few years, screening out the rhizomes has been introduced
* We have observed a number of market options to design alternative treatments which do not delay development program. These options, which include rapid insitu treatment, have minimal risk and can be conducted at around 25% of the cost to tip

Japanese Knotweed needs professional respect if you want to avoid re-growth and guarantee your actions.

After extensive research, methods have been developed for neutralising the growth of Japanese Knotweed within the soils matrix. The writer has been involved with various treatment protocols for over 16 years. Observations have shown results which have led to develop rapid integrated treatment. Japanese Knotweed rhizomes will not propagate easily when below a certain length and diameter; with the correct dosages of approved herbicide formulae applied directly onto the rhizome, growth can be neutralised.

The solution which allows treatment even in the winter months combines an understanding of the plant physiology with experience on historical eradication.

In simple terms a controlled excavation of the impacted area takes place to remove the plants and rhizomes. The excavated material is transferred into the treatment plant to reduce the rhizome mass to a none viable re-growth size with a simultaneous application of approved herbicide during the treatment cycle. The treated material is set aside or can be returned to the previously excavated pit.

This is just one example of forward thinking being applied. There is no doubt that invasive weed specialists will continue to field test innovative ideas to eradicate the problem within acceptable timescales in the ensuing years but with purposeful forward planning there are products and services available now and which work.

We are currently writing a “top tips” book on dealing with Japanese Knotweed and it will be available when completed and published through our website www.knotweed-uk.com

Patrick Horsley

Director – Invasive Vegetation Management & Treatment Ltd