Risk assessment of weeds.
Very few countries as yet use any formal Weed Risk Assessment process in deciding which plant species to exclude under their quarantine regulations, but all will be under increasing pressure to do so to satisfy international trade conventions. Recent revisions to international guidelines for the development of pest risk analysis are detailed. The systems already in use in Australia, USA and New Zealand are described and found wanting in some respects. The possibilities for improvements are considered in relation to the available literature on prediction of invasiveness and the main elements of any proposed system are outlined.