Parasitism of the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) and non-target weevils by Microctonus aethiopoides Loan (Hymenoptera: Braconidae) in south-eastern Australia, with an assessment of the taxonomic affinities of non-target hosts of M. aethiopoides recorded from Australia and New Zealand

Abstract  The braconid parasitoid Microctonus aethiopoides Loan has been released in Australia and New Zealand for biological control of the lucerne pest Sitona discoideus Gyllenhal. In New Zealand, the parasitoid attacks a number of endemic weevil species. A survey of Curculionoidea found in and near lucerne in south-eastern Australia was carried out to investigate whether similar non-target parasitism was occurring, and to relate this to levels of parasitism found in the target host, S. discoideus . Some of the original M. aethiopoides release sites were particularly targeted in the survey of 25 sites in Victoria, New South Wales and South Australia. Almost 2500 weevils were collected, of which over 90% were S. discoideus , with the remaining 197 other weevils comprising 29 species found at 15 of the 25 sites. Parasitism of S. discoideus by M. aethiopoides occurred at 12 lucerne sites, with levels ranging from 0 to 25%. A single incidence of parasitism of a species of an Australian native weevil Prosayleus sp. by M. aethiopoides was recorded. No parasitism of any other weevil species was observed. The taxonomic affinities between Sitona and native Australian and New Zealand weevils are discussed, concluding that non-target host range in M. aethiopoides may be determined more by ecological factors than by taxonomic affinities among its hosts.