Colony optimisation of Mastrus ridens (Hymenoptera: Ichneumonidae), a potential biological control agent of codling moth in New Zealand

Abstract

Mastrus ridens (Horstmann) (Hymenoptera: Ichneumonidae) was imported from Argentina into New Zealand as part of a classical biological control programme against codling moth (CM), Cydia pomonella (L.) (Lepidoptera: Tortricidae). A laboratory colony was successfully established and maintained in quarantine, and experiments were conducted to understand the biology and behaviour of the parasitoid to maximise its efficiency prior to release. Naïve females parasitised a maximum of four CM larvae/day, laying a total of 12.9±1.5 eggs. However, a single CM larva could support the development of a maximum of 10 parasitoids. The body sizes of emerging M. ridens females in the colony decreased with an increase in the number of pupae developing on a single CM larva, because of competition. Female M. ridens preferred larger CM larvae to smaller larvae in cocoons for oviposition. Superparasitism, host feeding and the number of CM larvae hosting damaged parasitoid eggs increased with decreasing host/parasitoid ratios.