Exotic beneficials in classical biological control of invasive alien weeds: friends or foes?

摘要

In many parts of the world classical biological control is commonly incorporated into an integrated management strategy to deal with invasive alien plant species. Countries such as Australia, South Africa, New Zealand and the USA have a long-standingexperience in implementing this control method; hence, their national regulatory pathways and legal frameworks are well-established and tested. In contrast, Europe has little experience of this management strategy, which involves the introduction of co-evolved and, thus, highly specific natural enemies (arthropods or pathogens), from the centre of origin of the invasive species into its new exotic range, with the aim of reducing its population below a certain threshold. The potential risks associated with the use of exotic organisms to control invasive alien species are of common concern and microorganisms are often perceived as especially problematic. Based on past biocontrol initiatives, particularly those using co-evolved fungal pathogens to controlinvasive alien weeds, as well as on experiences gained from two recent projects dealing with two European weeds: giant hogweed {Heracleum mantegazzianum) and Japanese knotweed (Fallopia japonica), this paper illustrates the stringent risk assessments undertaken for potential biocontrol agents and reviews existing guidelines and legislation regulating the introduction of such exotic beneficials.