INNSA Standard


Stem injection of Japanese knotweed is established and cost-effective means of Japanese knotweed treatment which can be used in most weather conditions and can minimise damage to other plants

  • All operatives carrying out stem injection works must hold (or be directly supervised by someone holding) a valid certificate of competence (e.g. NPTC PA1*), as well as the relevant award relating to the equipment being used (e.g. NPTC PA6INJ*).
  • INNSA Contractor Members offering invasive weed treatment should provide additional continued training to all site operatives. This training should provide specific information and techniques regarding all non-native invasive species which the site operatives will be required to treat.
  • Where chemical application works are carried out in or near to water, a relevant award (e.g. PA6INJ or PA6W8) must be held by a supervising member of the site team.
  • Operations being carried out near water should apply for and comply with Environment Agency (or the relevant local agency) water quality management requirements.
  • Herbicide mixing and application works should always be carried out using appropriate PPE specific to the task in hand.
  • Chemical application works should be carried out with a relevant policy in place to minimise the risks of cross-contamination, protect the environment and minimise any risk to water.
  • Companies should be forthcoming with customers about the risks and limitations of herbicide treatments.
  • Contractors should always provide a written method statement, risk-assessment and COSHH assessment for all herbicide application works that are undertaken.
  • Contractors should follow all statutory instructions, including the recommended dosage rates as specified on the herbicide manufacturers’ guideline (the product label).
  • Contractors should ensure that equipment is correctly calibrated prior to work commencing and maintained throughout the procedures.
  • A management plan should be in place to ensure all works have been completed successfully.
  • Surveying of the plants must be completed by the contractor prior to starting the contract to establish the potential success of the stem injection in the first season.
  • Previously treated Japanese knotweed, damaged or cut canes or small growth may take more than one season to treat and / or may need alternative remediation methods. All customers should be informed of this.
  • Companies should at all times maintain an awareness of current pesticide regulations and laws appropriate to their area(s) of operation and ensure all employees and sub-contractors are regularly updated, preferably through CPD accreditation.
  • Ground disturbance or excavation work within the contaminated areas and buffer zones will need the contractor’s consent prior to works commencing and may require additional remediation.

*further details available at: