REUTERS | Mike Blake

Japanese Knotweed: are its days numbered?

Following last year’s consultation, Huw Irranca-Davies MP, the Minister for the Natural and Marine Environment, Wildlife and Rural Affairs, has announced that a biological control will be introduced in the UK to try and limit the spread of Japanese Knotweed.

The Minister described the problems associated with Japanese Knotweed as “massive”, costing the economy in the region of £150 million a year to deal with it.

What is Japanese Knotweed?

Japanese Knotweed was first introduced to the UK in the nineteenth century as an ornamental plant and is now described by the World Conservation Union as one of the top 100 worse plant species. The Environment Agency describes it as “the most invasive species of plant in Britain”. It causes damage to the built environment (both buildings and hard surfaces) and creates huge headaches for contractors and developers on many building sites across the UK.

The Envionment Agency publishes a Code of Practice, which explains what Japanese Knotweed is and how to:

  • Prevent it spreading.
  • Manage it.
  • Treat it (through cuttting, burning, excavation or burial).
  • Dispose of it through landfill.

The Code also explains how the presence of Japanese Knotweed will affect a site in the long term.

Legislation puts a duty of care on landowners to be proactive in the control and eradication of Japanese Knotweed. All parts of the plant and any soil contaminated with it are classified as controlled waste and are required legally to be removed and disposed of by a licensed waste control operator.

Introducing a biological control

The Government plans to introduce a small insect that feeds on the sap of the plant, thereby weakening it and making it more susceptible to modern methods of treatment and erradication. The insect, a small psyllid called Aphalara itadori, is a native predator of the plant in Japan.

However, the insect will not be released country-wide. Initially, small, controlled sites will be used to test the effectiveness of the insect in the wild. For the last year or so, tests have been ongoing with native plants in laboratories to ensure no damage will be caused to native plants. Within 12-18 months, we should know whether the insect can be released further afield.

This will be the first time that a biological control has been officially released. Such releases are prohibited under the Wildlife and Countryside Act 1981.

For more information on the Government’s plans, you can listen to the interview with the Minister here. You can also read more about Japanese Knotweed on the Japanese Knotweed Alliance’s website.

One thought on “Japanese Knotweed: are its days numbered?

  1. Let’s hope that Aphalara itadori does not have any forseen effects on our already stressed environment. I am glad that it only being released on small, controlled sites but I hope that the small creatures do not manage to escape and cause havoc.

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