A. Chhagan

Effect of irradiation on female painted apple moth Teia anartoides (Lep., Lymantriidae) sterility and attractiveness to males

Abstract:  Live female painted apple moths are being used to monitor the distribution of this invasive species in Auckland as part of a major eradication effort, and the goal of this project was to develop a method to minimize the risk of unwanted live insect propagation from the trapping programme as a result of vandalism or ‘eco‐terrorism’. Female pupae were irradiated with a range of doses and their egg viability assessed, and also tested to determine the impact of irradiation on male moth catch in the field. Female painted apple moth pupae, irradiated at a range of doses from 100 to 500 Gy, were placed in cages in traps at 10 m spacings from non‐irradiated females, near a central release site of irradiated males. Untreated control females alternated along orthogonal transects with irradiated females. The results indicated no significant effect of female irradiation on catch of males. There was no correlation between dose and catch, within the range of exposures tested. There was a very low hatch rate of eggs from females irradiated at all doses tested (100–500 Gy). These results suggest that irradiated females could be used in traps to reduce potential risks of deliberate spread of the unwanted organism by activists, without affecting the effectiveness of monitoring males.

Host range testing for risk assessment of a sexually dimorphic polyphagous invader, painted apple moth

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

Host selection behaviour in Mastrus ridens, a gregarious ectoparasitoid of codling moth, Cydia pomonella

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.

Survival of the gregarious ectoparasitoid Mastrus ridens on codling moth, Cydia pomonella, and non-target species

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.

Efficacy of insecticides against the tomato/potato psyllid (Bactericera cockerelli)

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. F2 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.