Invasion Biology and Biological Control1

Abstract

Abstract Analysis of some current issues in invasion biology that relate to exotic pests illustrates the linkage between this discipline and biological control and reveals opportunities for invasion biologists and biological control workers to mutually advance their respective disciplines. Concepts such as the tens rule, early-stage subdectability, and long latency period from invasion to first detection should be viewed as working hypotheses rather than established principles of invasion biology. Analysis of California invasions by spotted alfalfa aphid [Therioaphis maculata(Buckton)] and Mediterranean fruit fly [Ceratitis capitata(Wiedemann)] suggests that such exotic insect pests are not necessarily good models for invasion biology. However, “planned invasions” of phytophagous insects for weed control may be appropriate models in certain cases. Research on how to increase environmental resistance to invasion has not received sufficient attention. Experience in biological control of weeds suggests that incumbent general predators may prevent the establishment of a founder population of an herbivorous insect. Thus, conservation and augmentation of natural enemies should be explored for precluding invasion by exotic pests or maintaining pest-free zones. For exotic insect pests that establish and are not eradicated, classical biological control should be a priority, particularly in perennial or stable habitats. Unfortunately, ecological theory has not provided predictive guidelines for practitioners of this method. At the same time, the need for a more predictive (or less empirical) approach to classical biological control has never been greater.