Establishment and dispersal of <i>Cotesia rubecula</i> a larval parasitoid of <i>Pieris rapae</i> in the Nelson district

Abstract

Cotesia rubecula is a solitary larval parasitoid of Pieris rapae the small white butterfly (SWB) and has become an important biological control agent in regions where it has established since its release into New Zealand in 1993 It was first released in the Nelson region at three sites on 15 April 2013 after a survey in 2010 failed to find the parasitoid The cocoons of C rubecula for this release came from collections of SWB larvae at a trial site at Pukekohe and from unsprayed forage brassica plants growing near Burnham midCanterbury Monitoring of C rubecula and the established parasitoid C glomerata took place over two seasons 201415 and 201516 with all stages of SWB larvae collected at five properties across the Nelson region from Richmond to Motueka C rubecula were recovered from two of the original release sites for the next two years and appeared to spread to another site 9 km away from any release site This parasitoid is considered to be established in the region and should disperse naturally to become an important biological control agent of SWB in most habitats