Non-Target Parasitism Of The Weed Biological Control Agent, Rhinocyllus Conicus Froelich (Coleoptera : Curculionidae) By, Microctonus Aethippoides Loan (Hymenoptera : Braconidae)

Parasitism of a number of non-target weevil species by the introduced biological control agent Microctonus aethiopoides has been reported in New Zealand. Amongst these is the introduced weed biocontrol agent Rhinocyllus conicus. Field-parasitised R. conicus have been recorded from five sites in Otago and South Canterbury. Exposure of R. conicus to M. aethiopoides in laboratory investigations gave parasitism levels similar to those found in the target host Sitona discoideus, Levels of parasitism measured in the field, however, ranged from 2 to 16 percent and were lower than those recorded for S. discoideus in the same environments. The current relatively low levels of field parasitism of R. conicas by M. aethiopoides suggest that the efficacy of R. conicus as a weed biological control agent is not being greatly compromised but more investigation of impacts and monitoring of parasitism levels will be required to understand the situation more fully.