Could research in the native range, and non-target host range in Australia, have helped predict host range of the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae), a biological control agent introduced for Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) in New Zealand?

摘要

It is generally accepted that knowledge of the natural and novel host range of proposed biological control agents can help to inform predictions of potential host range in new areas of introduction. To test this hypothesis, this paper describes a retrospective study conducted to contrast and compare the natural host range of Microctonus aethiopoides Loan (Hymenoptera: Braconidae) with its novel host range found in Australia and New Zealand, where it has been introduced to control the adult stage of the weevil Sitona discoideus Gyllenhal (Coleoptera: Curculionidae), a pest of lucerne. Surveys carried out in and near lucerne crops in Morocco and Australia each resulted in collections of over 3,000 weevils, of which respectively 84 % and 93 % were S. discoideus. The host ranges determined from these surveys for each M. aethiopoides population were then compared with information already available for field host range in New Zealand. In Morocco, species in the genera Sitona and Charagmus (Curculionidae: Entiminae: Sitonini) and Hypera (Curculionidae: Hyperinae: Hyperini) were found to be parasitised by M. aethiopoides. In Australia, an earlier record of non-target parasitism of ‘Prosayleus’ sp. 2 (Curculionidae: Entiminae: Leptopiini) is still the only known instance of non-target parasitism by M. aethiopoides. The known non-target field host range in New Zealand is much greater, comprising 19 native and introduced weevil species mainly in the subfamily Entiminae (tribe Leptopiini) but also in Curculioninae, Cyclominae and Lixinae. This is discussed in the context of predictions that could have been made at the time of introduction 30 years ago had the Moroccan and Australian data, modern molecular technologies and current understanding of weevil classification been available. The absence of Leptopiini in Morocco and the record of a native Australian leptopiine host could have indicated that native weevils in this tribe in New Zealand might be at risk of attack by M. aethiopoides.