Microctonus hyperodae a summary of releases and distribution in New Zealand pasture

Abstract

The braconid parasitoid Microctonus hyperodae was released in New Zealand for biological control of Argentine stem weevil Listronotus bonariensis The initial 1991 research introduction involved the release of 99000 parasitised L bonariensis Between 1991 and 1998 a further 660000 M hyperodae were released as part of commercial contracts and research programmes Commercial contracts resulted in the widespread release of the parasitoid in the North Island with South Island releases mainly confined to midCanterbury There were eight geographic populations originally collected from South America and these were maintained separately in the laboratory Excluding the Mendoza population which was founded on a single female an average of 91040 M hyperodae was released from each of the seven remaining populations Parasitised L bonariensis were released at a total of 121 sites and the parasitoid established at 118 (975) Based on the distribution of releases in New Zealand and the results of surveys it is estimated that M hyperodae is now very widely distributed in the North Island with more limited distribution in the South Island