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A wide known host range in Australia and novel herbivory on native and naturalized species in New Zealand supported the decision to commence a NZ$65 million eradication programme against painted apple moth [ Teia anartoides (Walker) (Lepidoptera: Lymantriidae)] in Auckland (1999-2007)., Laboratory no-choice tests were designed to examine the 'host' status of the associations seen in the field., Laboratory tests investigated 79 native and introduced plant species with 122 provenances. Forty-two percent of plants were capable of supporting larval development to adulthood, with male bias; 30% were defined as potential hosts with female larvae developed through to the pupal stage; > 10% survival indicated probable physiological hosts. Sporadic or more frequent attack of New Zealand native broom, and introduced lemon, apple, sycamore, walnut, cherry and poplar, was likely, with a wider range of hosts supporting male emergence., A few negative laboratory results contradicted field observations of significant damage by large numbers of larvae. The present study highlights the challenge faced with respect to predicting the ecological host range of invasive polyphagous species, whose biology is little known, during the early stages of a first invasion. The implications of a wider host range found in males than females are discussed. [ABSTRACT FROM AUTHOR]

The host-acceptance and oviposition behaviours of Mastrus ridens Horstmann (Hymenoptera: Ichneumonidae) on cocooned codling moth ( Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) and non-target tortricid larvae were characterised. Acceptance appeared to result from analysis of kairomones in the silken cocoon and not from the size or movement of the larva within. No larva of three non-target species ( Planotortix octo Dugdale, Grapholita molesta (Busck) and Cydia succedana (Denis & Schiffermüller)) was recognised by M. ridens, but a few larvae of Ctenopseustis obliquana Walker and Argyroploce chlorosaris Meyrick were accepted and eggs laid. Scanning electron micrographs of antenna and the ovipositor sheath revealed sensilla likely to be involved with host recognition. It appears that a female M. ridens can only locate a host within a habitat by encountering specific, contact chemical cues and by acoustical sounding. Generally, New Zealand’s native insects are not at risk because they are simply not recognised as possible hosts. [ABSTRACT FROM AUTHOR]

Survival in the laboratory of Mastrus ridens Horstmann (Hymenoptera: Ichneumonidae) reared on larvae of Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) and five species of non-target Tortricidae was compared. Clutch size (numbers of eggs per host larva) and survival were higher on codling moth than on non-target species, and most adults reared from non-target larvae were smaller. F 2 generation M. ridens adults reared on Argyroploce chlorosaris Meyrick and Cydia succedana (Denis and Schiffermüller) larvae were also small, with a sex ratio skewed to males. Few parasitoids survived, and they did not appear to have adapted to the non-target species on which their parents were reared. When M. ridens eggs were immediately removed from venom paralysed larvae, no codling moth larvae but most non-target larvae died within a few days. It is suggested that the host-paralysing venom of M. ridens is adapted to ensure the survival of codling moth larvae and is lethally maladapted to non-target species, such that it might be possible to determine ectoparasitoid host range by biochemical or physiological tools that characterise venom or prey response, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mastrus ridens is a specialist parasitoid of codling moth from its area of origin. • Laboratory populations differing in time in captivity differed in some fitness traits. • The most recent laboratory population from Chile had better fitness parameters. • F1 Females with a Chile mother had better fitness, with no effect of father origin. • There were no benefits of crossing populations, but there were maternal effects. Populations of natural enemies in classical biological control programs often undergo recurring bottlenecks during importation and rearing, which can result in lower genetic variability and fitness. Enriching colonies with wild individuals, multiple importations or combining populations from different origins may help reduce this problem. Mastrus ridens (Hymenoptera: Ichneumonidae), a gregarious idiobiont ectoparasitoid of codling moth (Cydia pomonella) larvae was introduced to New Zealand from laboratory colonies dating to the 1990s. To improve populations for release, individuals from a most recent collection were imported from Chile (CL). Tests were conducted to measure genetic diversity of the parental populations (F0) and fitness traits of pure and mixed combinations of NZ and CL populations for F0 and the F1 generations. Results showed several effects depending on the population origin. CL females and males in the F0 generation lived longer than NZ females and males. Offspring from a CL mother lived longer than those from a NZ mother, and F0 and F1 females from a CL mother parasitized more larvae than females from a NZ mother. Genetic diversity estimates of F0 CL and NZ populations were 24% and 17% heterozygosity, respectively, and the NZ population had a larger proportion of diploid males than the CL population. Thus, no improvement in reproductive output resulted by mixing NZ and CL populations, as hypothesized, but a maternal effect was found in this species. This study shows the importance of understanding and tracking imported populations' genetic diversity and fitness traits in classical biological control programs. [ABSTRACT FROM AUTHOR]