Department for Environment, Food and Rural Affairs
Printable version E-mail this to a friend

Insect could halt spread of alien weed

A tiny insect could be an effective and environment-friendly weapon against a damaging and costly invasive non-native plant, scientists have said.

Defra Ministers are seeking people’s views on proposals to release the non-native psyllid Aphalara itadori to help control Japanese knotweed (Fallopia japonica).  This plant has spread across Britain since being introduced as an ornamental plant in the early nineteenth century and costs the country millions of pounds in repairs to buildings, roads and railway lines.

The government is considering an application for a licence to release the psyllid to attack the plant to reduce its vigour, thus reducing the use of chemicals and the costs of control including weedkillers and physical removal. The cost of eradication nationally using conventional methods was estimated at £1.56 billion in 2003.

If a licence is issued, it is expected that the psyllid would be released and monitored at a small number of sites initially, followed by wider release in England and Wales.

Five-years’ research by scientists at CABI has shown that Aphalara itadori is the best candidate to help control Japanese knotweed in Britain.  The psyllid has been tested on 87 non-target types of plant including those closely related to Japanese knotweed as well as ornamental plants and important crops, to determine whether it will feed on other plants.  The findings suggest that only a few closely-related non-native knotweeds are potential hosts in Britain.

The research has been peer-reviewed by independent scientists and the Advisory Committee on Releases to the Environment.

To find out more go to Deadline for responses is 19 October 2009.

Notes to editors

  1. Japanese knotweed has been able to become highly invasive in Britain because it was introduced as an ornamental garden plant without the natural enemies which keep it in check in its native range of east Asia.  There are 186 species of plant-feeding insects and mites, including Aphalara itadori, associated with Japanese knotweed in its native habitats.  None of these has been found in Britain. 
  2. Research on biological control of Japanese knotweed has been carried out by CABI, a not-for-profit organisation specialising in agricultural and environmental research and who have expertise in developing biological control measures . The research was funded by British Waterways. Cornwall County Council, Defra, the Environment Agency, Network Rail, South West of England Regional Development Agency and the Welsh Assembly Government.
  3. Defra’s Food and Environment Research Agency (Fera) is the licensing authority for the Plant Health Act 1967 and for the release of non-native biocontrol agents under the Wildlife and Countryside Act 1981.
  4. The Welsh Assembly Government’s Department for the Environment, Sustainability and Housing is considering a licence to release the psyllid in Wales.
  5. The comments of the Advisory Committee on Releases to the Environment (ACRE) are at: The report of the further independent peer review will be published alongside the consultation documents on 23 July.


Public enquiries: 08459 335577
News releases available on our website:

Defra's aim is sustainable development

PDNS: Mandatory Active Cyber Defence for Public Sector Networks. Latest Guide