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Japanese knotweed is one of the most high profile and damaging invasive weeds in Europe and North America

        Japanese knotweed       Japanese knotweed growing through concrete       Stand of Japanese knotweed

The Department for Environment, Food and Rural Affairs (Defra) and the Welsh Government have approved the release of the psyllid, Aphalara itadori to help stop the spread  of Japanese knotweed.

The psyllid release programme began in Spring 2010 at two closely monitored sites in England. This, along with releases to outdoor cages, enabled safety testing in the field, which confirmed the extensive lab safety data. The next stage of the controlled country-wide release of the psyllid happened at eight carefully selected sites containing Japanese knotweed in England and Wales. Psyllids were released at these sites in 2011-2013. The sites, and paired control sites on which the psyllid has not been released, continue to be closely monitored. Sightings of psyllids at several sites in the Spring show that the psyllids can overwinter successfully. Large-scale field cage studies in 2014, where a greater number of psyllids have been released, confirm their safety at higher densities. It is hoped that establishment and population growth will follow, but this stage can take time.

CABI, who have undertaken the scientific research, are world experts in natural control. CABI has an excellent international track record for discovering, safety testing, and assisting governments release natural control agents. To find out more, visit

Watch an audio presentation by CABI's Dr Dick Shaw who gives an introduction to invasive species, natural control and how it can be used to control Japanese knotweed.    

For further information, please use the links above, or download an information pack which will provide you with information about the plant, the project and the scientific research carried out. 

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