Establishment and seasonal activity in New Zealand of Mastrus ridens, a gregarious ectoparasitoid of codling moth Cydia pomonella

Abstract

The establishment of Mastrus ridens Horstmann (Hym: Ichneumonidae) in New Zealand, from introductions in 2012–2015, was assessed in 2016. Two assessment techniques were used: (1) 10-cm wide corrugated cardboard trunk bands deployed throughout the summer and winter periods to catch wild codling moth larvae and their parasitoids; and (2) sentinel, laboratory reared, codling moth larvae, cocooned within narrow, 2-cm wide corrugated cardboard bands, deployed on a monthly rotation throughout the spring and summer. Trunk band recoveries showed at least a low rate of establishment of Mastrus ridens across the country. Mastrus ridens females attacked sentinel hosts from early spring (prior to pupation of wild hosts) until late autumn. This evidence for multi-voltinism (compared with one or two generations of their host) signals a potentially effective parasitoid. Four other codling moth parasitoids were also recovered frequently from either wild or sentinel codling moth larvae, with differences between regions. The extent to which they may disrupt or enhance biocontrol by M. ridens remains to be investigated.