Herbicide Treatment of Japanese Knotweed

Japanese Knotweed Treatment

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Our Japanese Knotweed Treatment Programmes provide professionally managed and executed herbicide treatment via knapsack spraying, stem injection and leaf-wiping.

Japanese Knotweed Treatment Programme

Often the most cost effective Japanese knotweed treatment and control method is a Herbicide Treatment Programme (HTP). An HTP involves methodical and carefully managed visits where the correct use of chemical over a sustained period of time will exhaust the plant and prevent the spread of knotweed which in turn will remove the risk of damage being caused to the property during the treatment period.

Our HTP is designed to cause maximum damage to the plant and achieve effective control in a short period of time. Suitable herbicides applied correctly can damage the knotweed crown and rhizome significantly enough to eventually prevent stem re-growth.

On completion of herbicide treatment, or as part of a Knotweed Management Plan, in most situations we are able to provide the treated site or property a Guarantee. Our Guarantee is available for periods of 2 to 10 years, with the duration being chosen by the customer in relation to their, or a third party's requirements (e.g. a mortgage lender requiring 10 years cover). Where guarantee periods of five or more years are taken out we can also provide Insurance on the Guarantee (i.e. an Insurance Backed Guarantee).

Japanese Knotweed Treatment Plan

There are several herbicide products on the market that can be used to combat Japanese knotweed and they have varying degrees of effectiveness, as well as differing impacts upon the surrounding land and vegetation.

When planning a Japanese knotweed treatment programme, we consider:

  • Proximity of Japanese knotweed to watercourses and bodies (inc the sea
  • Sensitivity to non-target vegetation (trees, plants and grasses) growing to the vicinity
  • Size of the infestation and density of the stand
  • Proximity of tree roots (if using residual herbicides)
  • Proximity of badger sets or other forms of protected wildlife

This enables us to determine the best choice of herbicide and the best method of application, which would be one or more of the following:

  • Knapsack sprayer (with highly directional nozzles)
  • Stem injector gun
  • Weed wiper

Japanese Knotweed Control - Limitations of Use

Unless the Japanese knotweed plant is small (a young/juvenile plant), it is unlikely that herbicide alone (whichever legal product is used and however it is applied) will remove 100% of the viability from the knotweed crown and/or underground rhizome system.

Disturbance of the stand area before, during or after treatment may therefore promote new growth from deep and/or dormant rhizome. It may also translocate knotweed material to other areas of the site (spreading the contamination) or result in un-licensed illegal removal of waste containing Japanese knotweed from site.

The Environment Agency recognises this limitation with herbicide and state:

'Japanese knotweed-infested soil that has been treated can be re-used for landscaping the site, but should not be taken off site, unless to landfill' (as controlled waste) (Property Care Association - Code of Practice.)

Therefore the following should be a key decision making criteria, when establishing the best treatment option for Japanese knotweed:

Is the area where the knotweed resides likely to be disturbed now or in the future?

If the answer is Yes (i.e. re-landscaping, small building works or full site re-development), then a remediation method involving physical extraction (i.e. excavation) and on or off site disposal of the plant may be required instead.

Legislation and Certification

There is a substantial amount of legislation concerned with the use of herbicides. Examples include the Control of Substances Hazardous to Health Regulations (COSHH) 1988 and the Code of Practice for Using Plant Protection Products 2006. The control of herbicide regulations can be found within the Food and Environment Protection Act (FEPA) 1985.

It is also a requirement that any intention to apply herbicide within 5-10 metres of a watercourse must not be carried out until written confirmation has been received from the Environment Agency. We undertake and obtain E.A. licenses to apply herbicide on or near water where required.

The application of any herbicides should only be carried out by persons with a recognised National Proficiency Test Council (NPTC) Certificate of Competence. This ensures the right herbicides are used and applied correctly. It is an offence to use non-approved products or to use approved products in a manner that does not comply with the specific conditions of approval. All our staff have the appropriate training and certification and conform to current legislation.

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