Laboratory Nontarget Host Range of the Introduced Parasitoids Microctonus aethiopoides and M. hyperodae (Hymenoptera: Braconidae) Compared with Field Parasitism in New Zealand

Abstract

Laboratory host specificity of 2 biological control agents, already introduced in New Zealand, was compared with actual field parasitism. The parasitoids were Microctonus aethiopoides Loan and Microctonus hyperodae Loan, braconids imported to control the curculionid forage pests Sitona discoideus Gyllenhal and Listronotus bonariensis (Kuschel), respectively. The nontarget weevil species tested included native, introduced, and beneficial species. M. aethiopoides oviposited in 11 of the 12 species to which it was exposed and successfully parasitized 9 species. M. hyperodae oviposited in 5 of the 11 species to which it was exposed and developed successfully in 4 species. Higher percentage parasitism was recorded with M. aethiopoides than with M. hyperodae . Field collections of weevils from Otago, Canterbury, and Waikato indicated that 10 New Zealand native species and 3 other nontarget species, including the weed biological control agent Rhinocyllus conicus (Froehlich), were parasitized by M. aethiopoides . M. hyperodae has been found parasitizing 1 native species, as well as Sitona lepidus Gyllenhal, which was accidentally introduced to New Zealand recently. In nontarget species, parasitism levels in the field of >70% have been recorded for M. aethiopoides and <5% for M. hyperodae . The results of this study suggest that laboratory host range testing is indicative of nontarget parasitism in the field.