The next stage of the controlled country-wide release of the psyllid Aphalara itadori, part of the scientific research project looking at biological control of the damaging invasive weed Japanese knotweed Fallopia japonica, has been completed.

Acting under licences granted by the Food and Environment Research Agency (Fera) in respect to England, and the Welsh Government in respect to Wales, not-for-profit science organization CABI has released the psyllid on behalf of the project board at a small number of carefully selected sites containing Japanese knotweed in England and Wales. These sites, together with a number of control sites on which the psyllid has not been released, will be closely monitored for five years.

This wider scale release follows years of rigorous testing in laboratories and has only been agreed thanks to good evidence of safety in open-field and field-cage studies last year.

The psyllid was identified by CABI as suitable for use as a biological control agent for Japanese knotweed. In its native Japan, Japanese knotweed presents few or no problems because natural controls have evolved to co-exist with it and provide a natural brake on its spread. Because it was introduced to Britain as an ornamental plant, it arrived here without any of these natural enemies, which is one of the reasons why it has been able to spread to such a great and damaging extent.

The psyllid was collected by researchers in Japanese knotweed’s native range in Japan. It lays its eggs on Japanese knotweed and the young then feed on the sap as they develop, reducing the plant’s ability to grow and spread. Tests have confirmed that it will not significantly feed or reproduce on any other plants, even if it is presented with no other choice, so it should not pose a threat to our native plants and wildlife.

The locations of the release sites and the control sites will not be disclosed in order to maintain the integrity of the ongoing research.

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