INVASION BIOLOGY AND BIOLOGICAL-CONTROL

Analysis of some current issues in invasion biology that relate to exo tic pests illustrates the linkage between this discipline and biologic al control and reveals opportunities for invasion biologists and biolo gical 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 w orking hypotheses rather than established principles of invasion biolo gy. Analysis of California invasions by spotted alfalfa aphid [Therioa phis maculata (Buckton)] and Mediterranean fruit fly [Ceratitis capita ta (Wiedemann)] suggests that such exotic insect pests are not necessa rily 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 biologi cal control of weeds suggests that incumbent general predators may pre vent the establishment of a founder population of an herbivorous insec t. Thus, conservation and augmentation of natural enemies should be ex plored for precluding invasion by exotic pests or maintaining pest-fre e zones. For exotic insect pests that establish and are not eradicated , classical biological control should be a priority, particularly in p erennial or stable habitats. Unfortunately, ecological theory has not provided predictive guidelines for practitioners of this method. At th e same time, the need for a more predictive (or less empirical) approa ch to classical biological control has never been greater. (C) 1998 Ac ademic Press.