C.B. Phillips

Transportation of nonindigenous species via soil on international aircraft passengers’ footwear

The potential for transported soil to harbour and spread nonindigenous species (NIS) is widely recognised and many National Plant Protection Organisations (NPPOs) restrict or prohibit its movement. However, surprisingly few studies have surveyed soil while it is in transit to provide direct support for its role in accidental introductions of NIS. Moreover, there are few border interception records for soil organisms because they are neither easily detected nor routinely isolated and identified. Better data would improve evaluations of risks from soil transported via different pathways, enable targeting of management resources at the riskiest pathways, and support development of new risk management methods. We surveyed organisms present in soil that had been removed from footwear being carried in the baggage of international aircraft passengers arriving in New Zealand and recorded high incidences, counts and diversities of viable bacteria, fungi, nematodes and seeds, as well as several live arthropods. These included taxa that have not been recorded in New Zealand and were therefore almost certainly nonindigenous to this country. In each gram of soil, there was an estimated 52–84% incidence of genera that contain species regulated by New Zealand’s NPPO, which suggests many were potentially harmful. Variation in the incidences and counts of soil organisms with sample weight, footwear type and season at the port of departure indicated it may be possible to develop methods for targeting management resources at the riskiest footwear. Comparisons with previously published data supported the hypothesis that survival of soil organisms is greater when they are transported in protected (e.g. in luggage) rather than unprotected environments (e.g. external surfaces of sea containers); this offers opportunities to develop methods for targeting management resources at the most hazardous soil pathways.

Genetic variation in Microctonus aethiopoides (Hymenoptera: Braconidae)

Abstract The Palaearctic parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae) has been introduced to North America for biological control of weevils in the genera Sitona and Hypera (Coleoptera: Curculionidae) and to Australia and New Zealand for control of Sitona discoideus Gyllenhal. Various geographic and host-associated populations of M. aethiopoides have exhibited differences in host preference, host range, and adult morphology. These differences have generally been interpreted as indicative of genetically differentiated biotypes of M. aethiopoides, but direct genetic evidence of biotypic variation has been lacking. Nucleotide sequence data were generated from the gene regions COI, 16S, 28S, and β-tubulin to assess genetic variation among M. aethiopoides reared from various host species collected in Australia, Iran, New Zealand, the United States, and 10 European countries. Ten adult morphological characters were also measured to validate the identity of the specimens and to assess morphological variation among the geographic and host-associated populations. Parsimony and maximum likelihood analyses of the COI, 16S, and β-tubulin sequences provided strong support for the presence of at least two M. aethiopoides biotypes, one associated with Hypera species and the other with Sitona species. There was also evidence for genetic divergence among parasitoids associated with different Sitona species. Morphological variation was also closely correlated with host species, but the occurrence of morphological variation in the absence of genetic variation suggested morphological characters should be used cautiously with M. aethiopoides biotypes.

The potential global distribution of the brown marmorated stink bug, Halyomorpha halys , a critical threat to plant biosecurity

The brown marmorated stinkbug, Halyomorpha halys is a highly polyphagous invasive insect, which has more than 300 reported hosts, including important horticultural crops. It has spread to every Northern Hemisphere continent, most recently to Europe. Whilst there have been no reports of incursions into Southern Hemisphere countries, there have been many interceptions associated with trade and postal goods. We modelled the potential distribution of H. halys using CLIMEX, a process-oriented bioclimatic niche model. The model was validated with independent widespread distribution data in the USA, and more limited data from Europe. The model agreed with all credible distribution data. The few exceptions in the distribution dataset appeared to be transient observations of hitchhikers, or were found at the edge of the range, in regions with topographic relief that was not captured in the climatic datasets used to fit and project the model. There appears to be potential for further spread in North America, particularly in central and southern states of the USA. In Europe, there is substantial potential for further spread, though under historical climate the UK, Ireland, Scandinavia and the Baltic states of Estonia, Lithuania and Latvia appear not to be at risk of establishment of H. halys. In the Southern Hemisphere, regions with moist tropical, sub-tropical, Mediterranean and warm-temperate climates appear to be at substantial risk on each continent. The threats are greatest in prime horticultural production areas.

The invasive Australian redback spider, Latrodectus hasseltii Thorell 1870 (Araneae: Theridiidae): current and potential distributions, and likely impacts

Populations of the Australian redback spider, Latrodectus hasseltii Thorell 1870, were first recorded in New Zealand in the early 1980s and in Osaka, Japan in 1995. Reliable records suggest that naturalised populations of L. hasseltii in New Zealand are present only in Central Otago and New Plymouth. In Central Otago, L. hasseltii feeds on endangered invertebrates, such as Prodontria modesta (Broun 1909). Latrodectus hasseltii is also a hazard to the New Zealand endemic L. katipo through interbreeding and competitive displacement. CLIMEXTM was used to model the potential global distribution of L. hasseltii based on current climate, and using ArcGIS® 9.2, areas of suitable climate in New Zealand were overlaid with favourable habitats to identify areas most suitable for L. hasseltii establishment. In addition, shelter that urban areas offer L. hasseltii were modelled in CLIMEX and incorporated into ArcGIS to produce maps indicating cities and built up areas where the species could establish. The presence of L. hasseltii in New Zealand and Japan, and its possible spread to other areas, is of human health significance, and the species may also impact on native biodiversity.

Progress in the search for biological control agents of clover root weevil, Sitona lepidus (Coleoptera: Curculionidae)

Abstract Clover root weevil, Sitona lepidus (syn. flavescens) (Coleoptera: Curculionidae), has recently arrived in New Zealand. It has emerged as a pest of white clover (Trifolium repens) in the central North Island and appears likely to spread throughout the country. This contribution describes efforts made in 1998 to source biological control agents of S. lepidus from Europe and North America. Six species of parasitoids (one nearctic, five palaearctic) have been recorded in the literature as attacking S. lepidus. Three species which warrant investigation as candidate biological control agents were identified in this study. These were the palaearctic species Microsoma exiguum (Diptera: Tachinidae), Microctonus aethiopoides (Hymen‐optera: Braconidae), and Pygostolus falcatus (Hymenoptera: Braconidae). Also, a preliminary description is provided of a disease which was observed to infect S. lepidus adults collected in California.

The potential of parasitoid strains in biological control: Observations to date on Microctonus spp. intraspecific variation in New Zealand

Abstract Over the last 15 years New Zealand researchers have been actively involved in the classical biological control of forage weevil pests. In the 1980s, the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) was successfully suppressed by the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae). Since 1990, an additional programme has been developed to examine the impact of the recently introduced parasitoid Microctonus hyperodae (Hymenoptera: Braconidae) on New Zealands worst ryegrass pest, the Argentine stem weevil ( Listronotus bonariensis (Kuschel)). The imported M. hyperodae founder populations were collected from a wide range of ecoclimatic zones. During both of the programmes, the importance of ecotypes has become increasingly apparent. The New Zealand M. aethiopoides population revealed phenological patterns quite different from those observed in Mediterranean Europe, North America and Australia. As a result of these observations, part of the current research into M. hyperodae has been developed specifically to explore ecotypic variation and its implications. This contribution reviews progress to date in researching ecotypic differences and comments on the potential of ecotypes in classical biological control, with particular reference to recently developed DNA-based techniques.

Potential effects of climate change on biological control systems: case studies from New Zealand

Biological control systems are integral to New Zealand’s success as a nation reliant on exporting quality agricultural, forestry and horticultural products. The likely impacts of climate change projections to 2090 on one weed and four invertebrate management systems in differing production sectors were investigated, and it was concluded that most natural enemies will track the changing distributions of their hosts. The key climate change challenges identified were: disparities in natural enemy capability to change distribution, lack of frosts leading to emergence of new pests and additional pest generations, non-target impacts from range and temperature changes, increased disruptions caused by extreme weather events, disruption of host-natural enemy synchrony, and insufficient genetic diversity to allow evolutionary adaptation. Five classical biological control systems based on the introduced species Longitarsus jacobaeae, Cotesia kazak, Aphelinus mali, Microctonus aethiopoides and Microctonus hyperodae are discussed in more detail.

South American origins of Microctonus hyperodae Loan (Hymenoptera: Braconidae) established in New Zealand as defined by morphometric analysis.

Eight South American geographic populations of the thelytokous parasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae) were released in New Zealand in 1991 to assist in the suppression of the pasture pest Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae). With one exception, parasitoids from each South American geographic population were released in equal numbers at each New Zealand release site. It was postulated that the South American geographic population(s) best suited to the conditions encountered at each New Zealand release locality would eventually become prevalent there. A morphometric analysis of adult parasitoids of known South American origins, reported previously, allowed M. hyperodae derived from west of the Andes (i.e. two collection sites in Chile) to be distinguished from parasitoids derived from east of the Andes (i.e. three collection sites in Argentina and one each in Brazil and Uruguay). Parasitoids derived from a fourth site in Argentina (S. C. de Bariloche) could...

Influence of host diet on parasitoid fitness: unravelling the complexity of a temperate pastoral agroecosystem

Parasitoid fitness is closely associated with the condition of the host insect, and the condition of the host is partly dependent on the quality and quantity of plant food available. The relationship between host diet and parasitoid fitness therefore has the potential to indirectly mediate complex multitrophic interactions. This relationship may be influenced both by the presence of mycotoxins from endophytic fungi, which share symbiotic relationships with plants and cause reductions in host‐plant quality for herbivores, and by the availability of beneficial nutrient‐rich plant foods such as pollen. This study used a multitrophic system involving ryegrass, a fungal endophyte, pollen, and an insect herbivore and its parasitoid to study the effect of host diet on parasitoid fitness. Previous studies showed that the larval stage of the parasitoid was negatively influenced by the presence of fungal‐derived alkaloids in the diet of its host, but no assessment of effects on the adult stage of the parasitoid had been made. Similarly, the effect of pollen in the diet of the host on the fitness of the parasitoid had not previously been examined. In this study, the fitness of parasitoids reared from hosts fed endophyte‐free ryegrass, endophyte‐free ryegrass plus pollen, or endophyte‐infected ryegrass was assessed in two laboratory experiments. Host insects exhibited significant responses to treatment, but remarkably, there were no significant treatment effects on parasitoid development times, the number of successful parasitoid emergences, tibia length, or preoviposition egg complement. The absence of a strong relationship between host diet and parasitoid fitness in this study differs markedly from studies of other parasitoid–host systems in that the adult stage of this parasitoid appears remarkably unresponsive to variation in host condition. This work contributes to a better understanding of multitrophic interactions and to the refinement of integrated pest management tactics in a temperate pastoral agroecosystem.

Intraspecific variation in the ability of Microctonus aethiopoides (Hymenoptera :Braconidae) to parasitise Sitona lepidus (Coleoptera: Curculionidae)

Abstract Sitona discoideus (Coleoptera: Curculionidae), a pest of lucerne (Medicago sativa), is controlled in New Zealand by the introduced parasitoid Microctonus aethiopoides (Hymenoptera: Braconidae). Unfortunately, a second Sitona species, S. lepidus (=flavescens), which has recently invaded New Zealand and has become a pest of white clover (Trifolium repens), is not parasitised by M. aethiopoides. Previous experiments have shown that New Zealand M. aethiopoides will attack S. lepidus, but its eggs appear to be killed by the host immune response. In contrast, M. aethiopoides has been observed to successfully parasitise S. lepidus in Europe. It is possible either that New Zealand S. lepidus has a more effective immune response to M. aethiopoides than European S. lepidus, or that New Zealand M. aethiopoides is less able to evade the S. lepidus immune system than European M. aethiopoides. An experiment was conducted to compare the suitability of French and New Zealand S. lepidus as hosts for French M. aethiopoides. This provided no evidence of S. lepidus intraspecific variation in host suitability for parasitism. Furthermore, amplification of inter simple sequence repeat (ISSR) regions of M. aethiopoides DNA demonstrated clear genetic differences between French and New Zealand M. aethiopoides. It was concluded that intraspecific variation in the ability of M. aethiopoides to evade the immune response of S. lepidus is the reason for the low levels of parasitism observed in New Zealand compared with Europe. Development rate data for M. aethiopoides larvae and pupae are reported.