Analysis of Classical Biological Control Programs

Abstract

As noted in Chapter 8, p. 128 or more pest insects and weeds have been completely or substantially controlled by imported natural enemies (Table 9.1). Some of these have been of minor or localized status, while others have been species of continental distribution and great economic importance. In certain cases success was attained with but modest effort, while in others success came only after elaborate preparation, dogged perseverance over many years, and great expense. Among the pest insects, by far the greatest number of successes have been scored against homopterous species, particularly diaspine and lecaniine scales. Some researchers have suggested that scale insects are particularly amenable to biological control because, being sessile during much of their life cycle, they cannot escape or avert natural enemies, and the colonies once found are vulnerable to maximum exploitation. But others point out that scale insects are particularly common pests of horticultural crops such as citrus, and that the considerable success against them may simply reflect the greater emphasis placed on biological control of such orchard pests. There is probably some validity to each contention, but this is perhaps irrelevant, for striking successes have also been scored against species of Coleoptera, Lepidoptera, Diptera, and Hymenoptera in a variety of situations. This is evidence enough that the chances for successful biological control exist across a wide spectrum of the major pest groups.