Question to the Department for Transport:

To ask Her Majesty's Government, for each of the last five years, (1) how many instances of infestation by Japanese Knotweed were recorded on Network Rail land and property, (2) how many complaints were received, and what was the cost to Network Rail of action taken to eradicate the species; (3) what action Network Rail takes in response to infestations and complaints about Japanese Knotweed; and (4) what action Network Rail takes in the event of this plant spreading from Network Rail land on to adjoining land and property.

1. Network Rail are currently in the process of gathering data about historical Japanese knotweed instances, however there are currently 5138 distinct sites with active treatment of Japanese knotweed.

2. The breakdown of complaints is as follows: 2019 – 25; 2018 – 62; 2017 – 42; 2016 – 72; 2015 – 73, not accounting for cases where a legal claim is made without a complaint. Some of these complaints developed into claims, with 170 claims made over the last 5 years. The total sum of these claim settlements amounts to £3.73m; this covers treatment costs as well as damages, investigation costs and legal costs. It was not possible to obtain figures for the overall expenditure on treatment, however it costs approximately £18-30 per metre square of knotweed to successfully treat it, over a period of 3 – 5 years.

3. In instances where Japanese knotweed is discovered, the location of knotweed is recorded and mapped, followed by treatment activity tailored to whether it is affecting safe operation of the railway and/or creating biosecurity issues. Measures such as boot and tool cleaning are undertaken to prevent further spreading of the knotweed. In carrying out these actions, Network Rail complies with the Lineside Vegetation Management Manual and relevant legislation.

4. In the event of Japanese knotweed having spread to third party land, Network Rail complies with UK legislation and deals with complaints as quickly as possible. If knotweed growth is visible at the boundary, or on both sides of the fence, permission will be sought from the third party for treatment and, if obtained, a management plan will be jointly agreed. Only herbicides using the active ingredient glyphosate are used in these instances.