Switching on the radio this morning, I was snapped out of the usual early-morning drowsiness by hearing CABI mentioned towards the top of the news bulletins. Among the usual stories of global financial meltdown, US presidential elections and the like, was news of how my scientific colleagues are hoping to bring Japanese knotweed, an aggressive invasive species, under control in the UK. (In fact I hear the breakfast show presenter on one of the national BBC radio stations said this story was a deliberate plan to distract us all from the financial crisis).
Even at this time of financial worries it appears that the story of how Japanese knotweed could be brought under control by introducing plant-eating predators from Japan has caught the public imagination: at the time of writing this it is tracked on the BBC news website as the ‘most emailed’ story, and for much of the day it has been in the top 3 most read articles. It describes how CABI biocontrol expert Dick Shaw and colleagues have been searching for natural enemies of the plant which was originally introduced as an ornamental species, but has since spread rapidly in the UK causing damage not only to native plant diversity, but also causing problems for hard structures, including buildings, paving stones and flood defence structures.
While it has been estimated that to remove all knotweed from the UK would cost several billion pounds, natural control could offer a much cheaper and more sustainable solution. After testing many insects and fungi from the plant’s home range in Japan, the CABI team narrowed the 186 insect and around 40 fungal species which are natural enemies to just two which attacked Japanese knotweed, but no other related or economically important plants found within the UK – a vital consideration if any species introduced as a means of control is not in turn to become a problem itself.
Some of the comments made on the BBC website in response to todays news story (and a mention of the oft-repeated cane toad story by the same radio presenter mentioned earlier) show that there is still public concern about biocontrol organisms becoming pests themselves. That is why there has been such extensive testing, in secure facilities, of all potential control agents before narrowing them down to one sap-sucking psyllid insect (Aphalara itadori) and a leaf spot fungus from the genus Mycosphaerella, which have been found to attack nothing but knotweed. Now the Department for Environment, Food and Rural Affairs (Defra) along with independent peer reviewers will assess the work before it is submitted for a public consultation. Only after exhaustive research and testing would government approval be given for a biocontrol programme.
As Dr Shaw says, we don’t know yet if the psyllid will turn out to be the "silver bullet" for knotweed control. But it could turn out, at the least, to be a cheaper and more sustainable way of keeping the weed from continuing its rapid spread than the current alternatives. And if it succeeds, it will be the first European use of biocontrol against invasive weeds.
For further information, see the Japanese Knotweed Alliance, or indeed the BBC news story which is part of a Special Report on invasive species from the BBC. See also the CABI website for details of more projects on invasive species control.