Initial establishment of the Irish strain of Microctonus aethiopoides in New Zealand

Abstract

Four experimental releases of the Parthenogenese strain of Microctonus aethiopoides from Ireland were made in early 2006 in the Waikato, Manawatu (two sites) and Hawke's Bay. By early winter, establishment was confirmed at all sites with parasitism levels exceeding 10% in the target host Sitona lepidus, a serious pest of white clover in New Zealand. Subsequent monitoring revealed considerable between-site variation. At the Hawke's Bay and Manawatu Feilding sites where overwintering weevil adults were still present in October, over 30% parasitism was found in newly emerged weevils in December 2006. In contrast, at the Waikato and Manawatu Bulls sites where there was no overlap of host generations, parasitism was below detectable levels during spring and early summer but recovered subsequently. The Irish M. aethiopoides appears to have four generations a year and diapauses over winter as a first instar larva. Following the initial success, releases have commenced in other regions.