INNSA Guidance assisting buyers of Japanese knotweed remediation services

UK Trade Body INNSA has released specific guidance to assist buyers of Japanese knotweed remediation services. This guidance will be particularly useful for local authority procurement departments, particularly in light of recent government intervention requiring that all amenity herbicide application is carried out by contractors who are members of the Amenity Assured scheme.

Following recent reporting of the “Swansea Japanese knotweed study”1 released in April 2018, INNSA noted widespread misreporting and misunderstanding of the results of the study, which is consistent with a lack of knowledge about this area of significant concern, which costs the UK economy over £160m every year.

‘There is still a huge amount of misleading advice and conflicting information out there.’ says Chris Oliver of JKSL, an INNSA Contractor Member ‘Even after the detailed results published in the Swansea study, we found a lot of the media were sensationalising and printing misleading headlines. This leads to more confusion for buyers and an inconsistent approach to tendering.’

‘Our advice is that Japanese knotweed can be remediated by an experienced specialist in line with the Environment Agency guidance and the INNSA Code of Practice.’ But Chris Oliver warned buyers: ‘Our members’ extensive experience does agree with the study findings that there is no “quick fix” solution to Japanese knotweed, and that herbicide treatment can take in excess of three years, even using appropriate products.’

INNSA encourage anyone who is specifying invasive species remediation works to use a registered INNSA Contractor Member to carry out the works to ensure the best quality advice and reliable works with the option of extended guarantees for up to ten years after completion.

As a minimum, INNSA recommend that buyers only use contractors who are members of the Amenity Assured scheme, both for quality assurance and to ensure that you are meeting your legal duties. This is in line with requirements issued in 2015 by the then Secretary of State for Communities and Local Government that UK Local Authorities must only use Amenity Assured contractors.

The Amenity Assured Scheme is run by BASIS, an independent standards-setting and auditing organisation for the pesticide, fertiliser and allied industries.

INNSA has drafted the following text that buyers can include in tenders that include invasive species work, as follows:

Contractors will be considered favourably where they can demonstrate membership of a recognised trade association such as INNSA (

The successful Contractor will be a member of the Amenity Assured scheme and will provide an in-date certificate demonstrating this. The Amenity Assured scheme is run by BASIS and further details can be found on their website

All INNSA Contractor Members are members of the Amenity Assured scheme.

INNSA is the UK trade body dedicated to the remediation of invasive species including Japanese knotweed.

0800 1300 485

  1. ‘Optimising physiochemical control of invasive Japanese knotweed’, Daniel Jones et al. [external link: ]

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