Plans to introduce plant-eating predators to fight a superweed spreading throughout Britain should not be seen as a 'magic bullet', says a world expert on Japanese knotweed at the University of Leicester.
Dr John Bailey of the Department of Biology has been researching the invasive weed since the 1980s. The research continues with PhD students Michelle Hollingsworth and Catherine Pashley. Research in the Leicester department established that the weed in Britain was a single clone- making it one of the biggest female organism in the world.
Dr Bailey has commented on plans announced this week to introduce a biocontrol to eradicate the weed that is plaguing Britain. The natural predator, a sap-sucking psyllid insect, is proposed to combat the weed. Plans have been submitted to the Government for approval.
University of Leicester scientists have previously liaised with the team behind the latest proposal including Dick Shaw, the lead researcher on the project, from Cabi, a not-for-profit agricultural research organisation.
Dr Bailey said: "Biological control is commonly used in the UK Glasshouse industry with a great deal of success. However, the use of predators invariably means that these die out when the prey levels get very low, and before the target is completely eliminated, so repeated applications are required.
"There is no doubt that in parts of the country Japanese Knotweed is still spreading along riversides and that in such areas it is extremely difficult to use herbicide – even supposing the will and the funding were available! Japanese Knotweed may be a big bully of a plant in Europe, but in Japan it is just one component of a giant herb community, and what we in the West think of as its almost profligate vigour is only enough to keep it in the game, struggling as it does to find somewhere to grow and to avoid the effects of the numerous predators that it attracts.
"A Biological control agent, as the developers themselves admit, is no 'magic bullet'. Certainly such a release will weaken existing plants and slow down or hamper range extension, it may even have the effect of reducing the amount of hybrid seed produced. But it must be viewed as an invaluable aid to levelling the playfield in the fight against this alien plant, rather than as a 'mission achieved'.
"If it is to be released it should be as part of a co-ordinated campaign which involves both public education of the dangers of inadvertently spreading the plant, and a redoubling of the use of more conventional control methods. To introduce a control agent and then sit back and let it do its work would lead to little reduction in the occurrence of the plant, and to a great increase in the unsightliness of its formerly pleasantly verdant appearance."
Dr Bailey travels widely on the subject of Japanese Knotweed; In September he addressed the Neobiota meeting in Prague with 'Opening Pandora's seed packet; unpredictable outcomes in indestructable plants?" Later this month he will be delivering 'Japanese Knotweed here today – here tomorrow?' at the BSBI Understanding our Alien Flora meeting in London.
NOTE TO NEWSDESK
For more information, please contact Dr Bailey on 0116 252 3386 or email jpb@le.ac.uk
Background notes:
Work on Japanese Knotweed at the University of Leicester by Dr John Bailey started in the 1980s and after the award of a PhD on the subject in 1989, the research continued with the able assistance of PhD students Michelle Hollingsworth and Catherine Pashley.
The original work of Dr Bailey established that all the Japanese Knotweed in Britain was octoploid (88 chromosomes) and that only female plants occurred. Extensive hybridisation was observed to be taking place between Japanese Knotweed and both Giant Knotweed and Russian Vine. The hybrid between Japanese Knotweed and Giant Knotweed (Bohemian Knotweed) is now known to be an important and hitherto under-recorded component of Japanese Knotweed populations. Fortunately for the inhabitants of these Islands the hybrid between Japanese Knotweed and Russian Vine, although perfectly viable and established in some localities, does not combine the vigour of each parent – rather they cancel each other out!
Michelle Hollingsworth's work took advantage of the newly emerging DNA Fingerprinting techniques, and was able to show that not only was all Japanese Knotweed female, but all belonged to a single clone, produced by cuttings from the original introduction by P. von Siebold in the 1850s – making it one of the biggest females in the world! Michelle was also able to show that small mutations in the chloroplast region of these plants gave us a clue to the region of origin. Catherine Pashley carried on this work with the intention of applying it to native Japanese plants to try and find out where the particular individuals in Europe had originated.
A collecting trip to Japan was arranged and plants collected from a wide geographical range. At this point they were contacted by Dick Shaw of CABI Biosciences, who was contemplating starting a Biological Control program for Japanese Knotweed. At a stroke the Japanese Knotweed research program that had been carried out from pure academic interest acquired an important and unforeseen application. Two of the basic tenets of Biological Control are 1 understand the plants you are working with and 2 search for Biocontrol agents in the area where the plants evolved. Cytological, morphological and historical work previously carried out at Leicester had shown that the European Japanese Knotweed was probably introduced from Japan as a garden plant by PF von Siebold from his nursery in Leiden in the 1850s. The molecular tools to discover the origin of Japanese Knotweed were in place and the trip to Japan already arranged. That Japanese Knotweed had been demonstrated to be a single clone and was thus lacking any population resistance was a bonus for a Biological Control Program. Like Britain Japan is not particularly large, but it is extremely long and straddles a number of degrees of latitude and has many different habitats. After an extensive search, our molecular research finally identified the origin of the European clone and collection of potential control agents was centred on this region.