Non-target parasitism of endemic weevils by introduced Microctonus (Hymenoptera: Braconidae) species in tussock grasslands of Otago and Southland, New Zealand

•Braconid parasitoids in the genus Microctonus were found to successfully parasitise endemic weevils in natural tussock grassland areas in southern New Zealand at altitudes higher than the pastures in which they were introduced.•The target hosts of these weevils are also found in these tussock grasslands, providing an opportunity for “spillover” parasitism, but it was also found that some cycling within native weevil communities occurs.•Nine endemic weevil species, mainly in the subfamily Entiminae were found to be parasitised mostly at levels below 10% although the highest level recorded was 36%.•Most non-target parasitism was caused by an Irish ecotype of Microctonus aethiopoides introduced to control Sitona obsoletus, a pest of clover. The parasitoids Microctonus aethiopoides Loan (Moroccan and Irish ecotypes) and M. hyperodae Loan (Hymenoptera: Braconidae) have been introduced to New Zealand as biological control agents for agricultural pest weevils Sitona discoideus Gyllenhal, S. obsoletus Gmelin and Listronotus bonariensis (Kuschel). These parasitoids are also present in native tussock grassland habitats and a survey carried out over two years at nine tussock grassland sites demonstrated that several endemic weevil species were parasitized by these biological control agents within these habitats. New records of non-target parasitism were found for the endemic species of Chalepistes, Nicaeana, and Eugnomus. It was found that M. aethiopoides is established and cycling within weevil communities in these environments, using endemic weevil hosts in part, but pathways also exist via three pest weevil species for spillover from agricultural environments. Parasitism of endemic weevils was not found to be ubiquitous in these environments and parasitism levels were mostly below 10%.