The potential of parasitoid strains in biological control: Observations to date on Microctonus spp. intraspecific variation in New Zealand

Over the last 15 years New Zealand researchers have been actively involved in the classical biological control of forage weevil pests. In the 1980s, the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) was successfully suppressed by the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae). Since 1990, an additional programme has been developed to examine the impact of the recently introduced parasitoid Microctonus hyperodae (Hymenoptera: Braconidae) on New Zealand's worst ryegrass pest, the Argentine stem weevil (Listronotus bonariensis (Kuschel)). The imported M. hyperodae founder populations were collected from a wide range of ecoclimatic zones. During both of the programmes, the importance of ecotypes has become increasingly apparent. The New Zealand M. aethiopoides population revealed phenological patterns quite different from those observed in Mediterranean Europe, North America and Australia. As a result of these observations, part of the current research into M. hyperodae has been developed specifically to explore ecotypic variation and its implications. This contribution reviews progress to date in researching ecotypic differences and comments on the potential of ecotypes in classical biological control, with particular reference to recently developed DNA-based techniques. (C) 1997 Elsevier Science B.V.