Evaluating plant pathogens for biological control of weeds: an alternativeview of pest risk assessment

Biological control of weeds is still a relatively new field in plant pathol ogy, in which, instead of trying to keep out exotic plant pathogens or to c ontain indigenous ones, they are actively being exploited in weed managemen t, particularly for alien invasives. Two broad approaches can be distinguis hed, although these are not necessarily mutually exclusive: classical or in oculative biological control, involving the importation and release of co-e volved, exotic pathogens from the centre of origin of the alien target weed ; and, inundative or augmentative control, whereby indigenous pathogens are mass-produced and applied as formulated products (mycoherbicides). This pa per attempts to identify and analyse the risks involved using examples from past and present weed-pathogen biocontrol initiatives, with an emphasis on Australian experiences.