Colony optimisation of <i>Mastrus ridens</i> (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 Nave females parasitised a maximum of four CM larvae/day laying a total of 12915 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

Interspecific competition between <i>Mastrus ridens</i> and <i>Liotryphon caudatus</i> ectoparasitoids of codling moth <i>Cydia pomonella</i>

“…However, more L. caudatus adults emerged than M. ridens adults suggesting the L. caudatus larvae were more successful in competition with M. ridens larvae. In this study, multiple eggs from both species (including more than a single clutch of M. ridens eggs) were often found on ccml, indicating that self-super parasitism (Sandanayaka et al 2011) and conspecific super parasitism occurred. Multi-species parasitism is clearly a disadvantage for the species that does not have the same competitive abilities when they both develop on the same host.…”

“…Host feeding may have had an impact on parasitoid larval development because no adults emerged from those ccml, possibly because the host died prematurely, thus depriving the parasitoid larvae of sufficient resources to complete development. Host feeding by both species (Sandanayaka et al 2011) may have resulted from a number of conditions, including adult malnutrition (Liu et al 2015). The failure of emergence from other ccml could not be explained.…”

“…Mastrus ridens and L. caudatus were reared at 22±1°C and 16 h photoperiod (provided by fluorescent lighting) in separate buildings, using the same methodology: the corrugated cardboard rolls containing cocooned codling moth larvae were placed into nylon mesh covered cages (40x40x40 cm) containing adult parasitoids and honey-agar diet and water. Cardboard rolls with parasitised codling moth larvae were removed and held in emergence containers (see Sandanayaka et al 2011 for full details of parasitoid rearing). Emerging adults were fed with honey-agar diet and water before being deployed in experiments.…”

“…Mastrus ridens was originally collected from Kazakhstan and brought to New Zealand from Argentina in 2009. Up to ten M. ridens larvae can successfully complete development on a single codling moth larvae (Sandanayaka et al 2011). Favourable rearing temperatures for M. ridens lie between 15°C and 25°C (Devotto et al 2010) and, at 22±0.5°C with adequate food and water, females can live for a mean of 27.2±1.2 days and are able to produce a mean of 58.5±4.5 eggs during an oviposition period of 14.3±0.6 days (Sandanayaka et al 2015).…”

“…If a female cannot determine if a larva has already been parasitized (or even if it can, but is not deterred from oviposition), then there is no behavioural competition per se for oviposition sites, and the consequent 'winner' of interspecific competition is determined by larval competition. Because both species are known to readily superparasitise larvae conspecifically (Cole & Walker 2011;Sandanayaka et al 2011), we tested the null hypothesis that females do not compete for oviposition sites, and will oviposit on codling moth larvae regardless of whether they have already been used for oviposition by another parasitoid of either species. We also investigated larval competition between M. ridens and L. caudatus when developing on the same host larva.…”