Not the Knotweed!

Japanese knotweed (Reynoutria japonica) is a highly invasive (mainly using its runners and stem fragments) escapee (it certainly belongs behind bars!) from gardens (it is claimed that its total biomass in the Swansea area exceeds 62,000 tonnes, equivalent to 40 Blue whales). It has now been reported that the Commonwealth Agricultural Bureaux International (CABI) are advocating introducing an 'alien parasite' to help curtail the spread of this plant in the UK (http://www.independent.co.uk/news/uk/this-britain/britain-calls-on-alien-parasites-to-take-fight-to-japanese-knotweed-821127.html). The 'parasite' in question is a jumping plant louse or psyllid (actually a sap feeder). Psyllids are already causing problems in Ireland where they were introduced along with Eucalyptus trees, so there are concerns that the 'parasite' might attack other native UK plants (CABI have tested the insect with a number of species and have, thus far, found no problem). Japanese knotweed damages our natural habitats as the sometimes 3M high growths completely shade the ground surface. It has been estimated that the eradication of this clone (all UK plants appear to be derived from one organism) by traditional means would cost £1.6bn so, getting an insect to do it, seems, at least, commercially attractive. Given the history of biological control disasters, however, one has to be a bit worried. I am also uncertain how these modest sap suckers could completely drain that biomass. The Western Mail picked up the story (http://icwales.icnetwork.co.uk/news/wales-news/2008/05/08/scientists-want-to-introduce-alien-louse-to-kill-japanese-knotweed-91466-20877161/).