Establishment and dispersal of Microctonus hyperodae Loan (Hymenoptera: Braconidae) in Otago and Southland

Abstract

During 1991-2 Microtonus hyperodae was released at four sites in Otago and Southland, New Zealand, as a biological control agent of Listronotus bonariensis (Argentine stem weevil). The parasitoid was first recovered from the field 17 and 19 months after release at Ophir and Sutton respectively. By April 1996 parasitism levels in L. bonariensis had reached 40% at Ophir and 33% at Sutton but radial sampling indicated that dispersal was limited to within a 1 km radius at Ophir and a 500 m radius at Sutton. No parasitism of non-target weevils by M. hyperodae has been recorded at either site. To date M. hyperodae has not been recovered from release sites near Mosgiel and Gore. The establishment levels and dispersal rates in Otago are less than those measured in Canterbury and Waikato and possible reasons for this are discussed.