Introduction

There are currently two ways in which an exotic pathogen may be introduced into a country for biological control of a pest. It may enter as a ‘classical’ introduction, to be released and established for continuing control of a (usually exotic) pest, or it may enter as a formulated pesticide, either registered or in an experimental form. Either way, when released in the field, there is a likelihood of its establishment. There is a need, therefore, in both cases, to ensure that such introductions are safe to the environment, and pose acceptable risks to non-target organisms.

Introducing exotic pathogens – the classical precedent

Over the past century, the classical biological control of insect pests and weeds has been dominated by the introduction of insect control agents (see Hopper, Chapter 6; and Blossey, Chapter 8). The use of pathogens in classical biological control has been limited, but it is increasing as we come to understand more about the biology of pathogens and see the positive results from a handful of successful programmes.

Against insects pests, the success of the baculovirus of Oryctes rhinoceros on Pacific and Indian Ocean islands is well-known (Bedford, 1986). More recently, a number of exotic introductions have been made against other insect pests, including some cnew associations’. For instance, the fungus Entomophaga praxibuli has recently been introduced into the US from Australia for grasshopper control (Anon, 1989) and an isolate of Entomophaga grylli has been introduced from Australia to the US against the indigenous grasshopper, Phaulacridium vittatum (Milner, 1985).