A trial release of a tiny Japanese insect has been sanctioned by DEFRA to try to control the spread of Japanese Knotweed, a rapidly growing introduced plant that reportedly costs over £150 million per year to control.

In its native Japan the plant does not rage out of control as it does here, suggesting that there must be biological controls in place in the local ecosystem. CABI, a not-for-profit organisation that uses scientific expertise to solve agricultural and environmental problems, investigated nearly 240 of the target species’ natural predators in order to find one that would feed on Japanese Knotweed and nothing else.

The best control agent was found to be Aphalara itadori, a psyllid that stunts the growth of the plant by feeding on its sap. The tiny insect only fed on the target plant during the experiments, even leaving very close relatives of Knotweed alone. In theory, the rest of the British ecosystem should be left alone by the insect, but contingency plans are in place to in case of any unforeseen circumstances.

My belief is that in order for the weed to be truly controlled, one predator will not be enough. If it takes 240 species to control it in Japan, why will one insect do the job here?

The trial release will take place in a handful of isolated sites, with further releases planned for the future if phase one is successful. It is the first instance of biological control, the use of a natural predator to control an invasive species, being attempted in the EU so it is unclear how it will pan out, but if you ask me I do not think this will work, but we will have to wait a few years to see the full results.