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Japanese Knotweed - JAPANESE KNOTWE JAPANESE KNOTWEED ESE KNOTWEED

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Japanese Knotweed - JAPANESE KNOTWE JAPANESE KNOTWEED ESE KNOTWEED Powered By Docstoc
					JAPANESE KNOTWEED


BASIS reg.: E/5620/ICMAH

                                       )
Japanese knotweed (Fallopia japonica) is an herbaceous perennial described by
                         allopia
                         invasive
scientists as the most invasive plant in Britain today. This Invasive Alien Species
(IAS) can grow vigorously at rates of up to 10 c centimetres per day to form dense
stands up to 3 metres in height, forming impenetrable leaf canopies and mats of
decomposing leaves during autumn that smother native species and lower habitat
         sity.
biodiversity. The threat of Japanese Knotweed to native plants and the construction
industry has been widely recognised and is covered by legislation surrounding its
                       removal.
handling, planting and removal

  In the UK it is an offence under the Wildlife and Countryside Act to ‘plant or
               otherwise cause the growth of the plant in the wild’.

 The plant reproduces vegetatively in the UK via underground rhizomes capable of
  extending 3 m in depth and 7 m laterally and exposing weakness in engineered
                               foundations
  structures such as building foundations and underground services. This causes
   major delays in building projects and escalating costs for developers. The cost
estimated by DEFRA to eradicate all UK Japanese Knotweed infestations was £1.56
                                        billion.

                                  functionally
Although Japanese knotweed is functionally dioecious (meaning a plant species with
  separate male and female individuals) in its native Asia, only female plants have
been recorded in so far in the UK. However the plant is proving a successful invader
                                               small
     despite this, with rhizome fragments as small as 0.7 g in weight potentially
                           developing into a new infestation.

Dispersion of Japanese Knotweed is by transportation of rhizome fragments in wind,
along water courses and by animal movement. However, it is mainly anthropogenic
                          onveyance
 activities such as the conveyance of contaminated soil material by plant and other
machinery that contributes to the successful invasion of this species on development
 sites. This highlights the imperative importance of strict hygiene procedures during
                               zones
  works within contaminated zones to prevent spread of the plant to the wider site.

                      FOR CONTROL AND MANAGEMENT OPTIONS
      PLEASE SEE OVER F    ONTROL
                             Control and Management

1. Environmental Clerk of Works
The most cost effective solution to a Japanese Knotweed infestation where the plant is
unavoidably associated with proposed earthworks or a building footprint is the provision by
an appropriately accredited company of an ‘Environmental Clerk of Works’. This service
                                                                             zones.
provides specialist advice and supervision of activity within contaminated zones. Developers are able,
under supervision, to utilise their own plant and operatives, significantly reducing cost and disruption
to build timetables whilst complying with their ‘Duty of Care’ obligations and law as it is stated in the
Wildlife and Countryside Act.

Following excavation, the Environmental Clerk of Works can provide advice on reducing landfill costs
                                                                                   pre-prepared area for
or supervise relocation of contaminated material to an on site lined burial pit or pre
                                      chemical
surface stockpiling and subsequent chemical treatment followed by final reincorporation into soft
landscaping.

2. Chemical
The main method of effective control against Japanese knotweed is by excavation and/ or
translocatory chemical herbicides. Chemical treatment is successful over time and, dependant
                                             killed
on the herbicide used the plant may be killed within one growing season. However sensitive
waterside sites and those with protected trees may take up to 5 years to clear of the plant, using non
persistent chemicals to preserve the environment.

  y
By law all chemical treatment must be performed by NPTC qualified spraying operatives and it is
recommended that practitioners are qualified to BASIS level, a presently voluntary indicator of service
                                                           become
quality and environmental compliance which is likely to become a valuable benchmark as economic
conditions tighten and the offering of ineffective ‘quick fix’ solutions becomes more tempting to less
scrupulous operators.

3. Excavation

Excavation and removal to licensed landfill is the most effective method to achieve complete
and immediate eradication, however this can prove prohibitively expensive, especially with the
upcoming    phasing     out   of  landfill    tax   exemption     for  contaminated     soils
                                                                                        soils.

Selective excavation of areas of growth only associated directly with building activities in conjunction
with chemical treatment will limit time delays and costs associated with removal of material to landfill,
while keeping client operations in contaminated areas within the law; thus allowing developers to
                  bust
develop a more robust build timetable.

Other methods such as encapsulated burial on site and formation of stockpiles of material on root
deflecting barriers, followed by chemical treatment over a period of months before reincorporation into
                                have
development soft landscaping hav also proved successful.

4. Biological Control
Recent research has indicated an important role for biological methods of controlling Japanese
Knotweed, especially on environmentally significant and sensitive sites not intended for commercial
development. Presently such research is concentrated on fungal pathogens and beetle predators of
                                                   bio-control
the plant and although as yet no effective bio control strategy is commercially available ADK is
                                                                                     h
working alongside CABI in this area. ADK would be interested in working with clients on sensitive
sites with their University backers as field trials for potential bio control management measures.

For further information on Japanese Knotweed remediation, contact Dr Emma Morley by
                                                        environmental.co.uk
phone on 01524 510599 or by email to emma.morley@adk-environmental.co.uk to discuss
individual site requirements and timescales.

				
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