Abstract
This chapter aims to allay the fears and the controversy, in particular the 'pathophobia' that inevitably surrounds the use of plant pathogens, and to provide the many and varied stakeholders, as well as decision makers, involved directly or indirectly in weed management with up-to-date information on the 'state of the art' of biological control of invasive alien weeds involving the classical approach. The current status of inundative biological control using bioherbicides is also discussed, with an emphasis on the progress achieved over the past four decades and, in particular, on how the concepts have changed over time.