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Pea weevil (Bruchus pisorum (L.), Coleoptera, Chrysomelidae) is a major cosmopolitan pest of pea crops and is established in most pea growing areas of the world. Pea weevil has been detected several times in New Zealand, but these incidents never resulted in an established population. Establishment occurred in 2016, when pea weevil was detected in stored and field peas in the Wairarapa region of the North Island. After due consideration, including initial delimiting surveys and analysis of potential pathways, the Ministry for Primary Industries (MPI), in consultation with industry and community interests, decided to attempt eradication. The eradication programme utilised a range of tactics including a regionalised pea growing ban, movement restrictions for pea plant material, pea trap crops managed with insecticides and herbicides, and physical pea plant destruction to prevent regrowth. Trap crops played a dual role for local surveillance and beetle destruction. A national survey for pea weevil was also undertaken. The eradication programme was implemented under national New Zealand legislation (including a Controlled Area Notice) and an awareness raising media campaign. The initial pea weevil infestation was found over an area of approximately 115,000 ha. National surveillance resulted in no pea weevil detections outside of the Wairarapa Controlled Area. In the first year of the eradication programme (spring 2016–2017), the pea weevil population was reduced by 99.1%. Zero detections of pea weevil were found in the spring of 2018 and 2019, confirming eradication, and the planting ban and movement restrictions were lifted in 2020. This paper details what appears to be the first documented eradication of pea weevil anywhere in the world and explores the technical challenges, options, and tactics which eventually led to this successful eradication.

It is well understood that damage by insect pests can have serious consequences for pasture resilience. However, the impacts of climate change on pastoral systems, the responses of insect pests, and implications for pest impact mitigation are unclear. This paper reviews pest responses to climate change, including direct impacts such as temperature and carbon dioxide levels, geographic range expansion, sleeper pests, and outbreaks resulting from disturbance such as drought and farm system changes. The paper concludes with a plea for transdisciplinary research into pasture resilience under climate change that has insect pests as an integral component – not as an afterthought.

Invasions by non-native pests and diseases represent serious threats to biodiversity, agriculture and human health. Under current border arrival rates associated with international trade not all such invasions can be prevented, so early detection and eradication (forced extinction) are important strategies for preventing establishment and long-term impacts. Removal of host plants has historically been a common tool used alone and in concert with other tools for eradication of plant pests but there is little scientific theory specific to the management of invasive species to guide the application of this eradication strategy. We drew upon extensive conservation biology literature documenting the effect of habitat destruction or fragmentation driving extinction. We applied a previously developed spatially explicit model of gypsy moth, Lymantria dispar, spatial dynamics to explore how fragmentation affects population persistence. This model accounts for a component Allee effect driven by mate-finding failure that interacts with dispersal. We observed a nonlinear dependency of population persistence on the fraction of habitat cover and the level of habitat fragmentation. Simulation of active habitat fragmentation via the removal of habitat in swaths of varying widths or the application of pesticide in varying swaths showed that removal of hosts or pesticide application in narrow swaths (i.e. 40 m wide) caused the greatest probabilities of extinction. Generally, habitat removal was more effective than one-off pesticide treatments at causing extinction. Synthesis and applications. Spatially explicit modelling of Allee dynamics in invading gypsy moth populations showed that host removal can be an effective method to eradicate invasive plant-feeding insects especially when habitat fragmentation is applied at a desirable level. Furthermore, this can be used as an alternative to, or in conjunction with, pesticide treatments, to provide more options for carrying out eradications and to increase the probability of eradication success.

Macrolophus pygmaeus, a predatory mirid used to manage greenhouse whitefly, was illegally imported into New Zealand, and for a time was reared and sold to commercial tomato growers. We designed and implemented a risk-based detection survey to determine whetherM. pygmaeuswas still present in New Zealand a decade later. The survey was designed to have an 80% chance of detecting a single low density (0.05 per lineal metre of host plants) population within 1 km of known points of introduction. The survey was implemented between 8 and 15 March 2018. Local habitat constraints meant that the planned sampling had to be modified but this was accounted for in the subsequent analysis. NoM. pygmaeuswere found in the samples, but 93 specimens from seven other mirid taxa were detected, validating the sample methods. The survey gives 60% confidence thatM. pygmaeuswas not present at a mean density of 0.05 per lineal metre of habitat. It gives 80% confidence that a population at 0.1 m−1was not present and 90% confidence that no population exists at >0.18 m−1. Though there are no published data on typical field population densities ofM. pygmaeus, for related species the survey would have had high confidence in detecting any medium to high density population present. Therefore, it is likely thatM. pygmaeusis no longer present in New Zealand, but if extant within the sampled areas then we have high certainty that it was at low densities compared to other predaceous mirids.

Early detection of biological invasions is necessary to enable successful management responses, such as containment and eradication. Several nations operate risk-based surveillance systems for early detection and proof of freedom from economically damaging pests and diseases. Identifying the best times of year to deploy and remove surveillance traps is important for maximising the probability of detection while minimising the economic costs of large-scale trapping. We modelled seasonal population dynamics to identify which days of the year contribute most to surveillance sensitivity and therefore the appropriate trapping period, and applied this to trapping for fruit flies (Diptera: Tephritidae) in New Zealand. Optimum trapping periods were defined as the minimum contiguous dates which would give a specific proportion (80%, 90%, 95%, or 99%) of the probability of detection compared to year-round trapping. Seasonal dynamics were based on an empirical model for the effect of temperature on population increase and decline, fitted to published data from around the world. The model suggested Mediterranean fruit fly (Medfly) should be trapped in the upper half of the North Island from at least November through May. Additional trapping in October and June may be warranted in the far north. Favourable microclimates or climate change to 2040 may allow Medfly populations to establish as far south as Christchurch and Alexandra, where trapping should run from mid December to early May. Queensland fruit fly (Qfly) and oriental fruit fly were unlikely to establish south of Napier and optimum trapping times for these species are approximately mid November through May. Climate change under moderate scenarios is unlikely to significantly alter the optimum trapping periods until at least 2040. The results were not sensitive to assumptions about trap efficacy and founder population size. However, they are based on simplified relationships between the intrinsic rate of increase and temperature. This approach is applicable to any invasive species with seasonal variation in surveillance efficacy. In response to this work, New Zealand's biosecurity authority has changed the seasonal timing of their fruit fly trapping to optimise detection efficacy.

Nonnative plant pests cause billions of dollars in damages. It is critical to prevent or reduce these losses by intervening at various stages of the invasion process, including pathway risk management (to prevent pest arrival), surveillance and eradication (to counter establishment), and management of established pests (to limit damages). Quantifying benefits and costs of these interventions is important to justify and prioritize investments and to inform biosecurity policy. However, approaches for these estimations differ in (1) the assumed relationship between supply, demand, and prices, and (2) the ability to assess different types of direct and indirect costs at invasion stages, for a given arrival or establishment probability. Here we review economic approaches available to estimate benefits and costs of biosecurity interventions to inform the appropriate selection of approaches. In doing so, we complement previous studies and reviews on estimates of damages from invasive species by considering the influence of economic and methodological assumptions. Cost accounting is suitable for rapid decisions, specific impacts, and simple methodological assumptions but fails to account for feedbacks, such as market adjustments, and may overestimate long‐term economic impacts. Partial equilibrium models consider changes in consumer and producer surplus due to pest impacts or interventions and can account for feedbacks in affected sectors but require specialized economic models, comprehensive data sets, and estimates of commodity supply and demand curves. More intensive computable general equilibrium models can account for feedbacks across entire economies, including capital and labor, and linkages among these. The two major considerations in choosing an approach are (1) the goals of the analysis (e.g., consideration of a single pest or intervention with a limited range of impacts vs. multiple interventions, pests or sectors), and (2) the resources available for analysis such as knowledge, budget and time.

CRISPR gene drives have potential for widespread and cost-efficient pest control, but are highly controversial. We examined a potential gene drive targeting spermatogenesis to control the invasive common wasp (Vespula vulgaris) in New Zealand. Vespula wasps are haplodiploid. Their life cycle makes gene drive production challenging, as nests are initiated by single fertilized queens in spring followed by several cohorts of sterile female workers and the production of reproductives in autumn. We show that different spermatogenesis genes have different levels of variation between introduced and native ranges, enabling a potential ‘precision drive’ that could target the reduced genetic diversity and genotypes within the invaded range. In vitro testing showed guide-RNA target specificity and efficacy that was dependent on the gene target within Vespula, but no cross-reactivity in other Hymenoptera. Mathematical modelling incorporating the genetic and life history traits of Vespula wasps identified characteristics for a male sterility drive to achieve population control. There was a trade-off between drive infiltration and impact: a drive causing complete male sterility would not spread, while partial sterility could be effective in limiting population size if the homing rate is high. Our results indicate that gene drives may offer viable suppression for wasps and other haplodiploid pests.

The problem of forest insect invasions is intensifying. Non-native forest insects are invading virtually every world region, and many are causing severe ecological and economic impacts. Biosecurity programs provide for intervention at various stages of the invasion process in order to mitigate the invasion problem. While preventing initial arrival of non-native insect species is a sound approach, such prevention is not always possible so additional measures are needed to manage invasions. Surveillance coupled with eradication is a valuable strategy for preventing the establishment of many new and potentially damaging species. Once non-native species are established, containment measures can be implemented to stop or slow the spread of these species in their non-native habitat. Here, we review how eradication and containment can be carried out as strategies for managing forest insect invasions. Several hundred programs have been implemented to eradicate non-native forest insects, with most programs proving successful. The vast majority of these eradication programs were implemented from 1970 onward. Pheromone-baited traps play a key role for detection and delimitation in most successful eradication programs. The isolation and synthesis of pheromones provided a key technology that facilitated forest insect eradications starting in the 1970s. Several examples are provided that illustrate both successful and failed eradication and containment programs. Consideration of historical experiences suggests the conditions that may lead to either success or failure of eradication and containment efforts.

Pest risk analysts frequently ask if the climate of a pest risk analysis area could be suitable for the establishment of an organism of concern. Species distribution models can help to answer this question, but constructing them is technically complex, time consuming, and uninformative for additional non-modelled species. A quicker more broadly applicable approach involves using environmental distance metrics, including climate matching algorithms such as the ‘match climates regional’ function of CLIMEX (CLIMEX-MCR), to generate indices of climatic similarity between different locations without reference to particular species. Several studies have shown that various environmental distance metrics can provide biologically meaningful results. However, the veracity of the CLIMEX-MCR algorithm remains unevaluated, despite its application in numerous published studies. We used CLIMEX-MCR and high resolution New Zealand climate data to measure climatic similarities between New Zealand and the rest of the world. We then tested the veracity of the climatic match estimates by evaluating if their predictions regarding the suitability of New Zealand’s climate for 43 non-native ant species corresponded with empirical observations of those species in New Zealand. Non-native ants that are, or were once, established outdoors in New Zealand had overseas distributions that were climatically well matched with New Zealand. In contrast, species that either are established only indoors in New Zealand, or were observed to temporarily nest outdoors then die in New Zealand, had overseas distributions that were poorly matched. Species that are frequently intercepted at New Zealand’s border, but are not established there, generally also had overseas distributions with low climatic similarities to New Zealand. We also measured climatic similarities between New Zealand’s 13 national parks and the rest of the world. The overseas distributions of the non-native ants showed poor climatic matches with New Zealand’s national parks, which was consistent with the absence of persistent outdoor non-native ant populations in those parks. Our results support the utility of CLIMEX-MCR algorithm for pest risk analysis.

Several tephritid fruit flies have explosive population growth and a wide host range, resulting in some of the largest impacts on horticultural crops, reducing marketable produce, and limiting market access. For these pests, early detection and eradication are routinely implemented in vulnerable areas. However, social and consumer concerns can limit the types of population management tools available for fruit fly incursion responses. Deterministic population models were used to compare eradication tools used at typical densities alone and in combination against the Queensland fruit fly (‘Qfly’), Bactrocera tryoni. The models suggested that tools that prevent egg laying are likely to be most effective at reducing populations. Tools that induced mortality once Qfly was sexually mature only slowed population growth, as successful mating still occurred. Release of sterile Qfly when using the sterile insect technique (SIT) interferes with the successful mating of wild flies, and of the tools investigated here, SIT caused the greatest reduction in the population at the prescribed release rate. Used in tandem with SIT, protein baits slightly improved the rate of population reduction, but the male annihilation technique (MAT) almost nullified control by SIT due to the mortality induced on sterile flies. The model suggested that the most rapid decrease in population size would be achieved by SIT plus protein baits. However, the model predicted both the SIT and protein baits when used alone would result in population reduction. The MAT can be used prior to SIT release to increase overflooding ratios.

A theoretical debate about whether parasitoids should be time or egg limited now recognizes both as feasible, and interest has turned to determining the circumstances under which each might arise in the field, and their implications for parasitoid behaviour and evolution. Egg loads of parasitoids sampled from the field are predicted to show a negative response to host availability, but empirical support for this relationship is scarce. We measured how a parasitoid's egg load responded to seasonal fluctuations in host population density and recorded the predicted correlation. In early summer, parasitoids were at high risk of time limitation due to low host availability, and in late summer, their offspring were at greater risk of egg limitation due to high host availability. Despite clear seasonal changes in selection pressures on egg load and lifespan, the parasitoid showed no evidence of seasonal variation in its reproductive strategy. We made minor modifications to a previously published model to explore the effects of seasonal variation in host availability on optimal investments in eggs and lifespan and obtained several new results. In particular, under circumstances analogous to some of those observed in our field study, temporal stochasticity in reproductive opportunities can cause investments in eggs to increase, rather than decrease as previously predicted. Our model results helped to explain the parasitoid's lack of a seasonally varying reproductive strategy. Understanding the evolution of parasitoid egg load would benefit from a shift of research emphasis from purely stochastic variation in parasitoid reproductive opportunities to greater consideration of host dynamics.

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.

Data from 190 plant pathogen eradication programs in the Global Eradication and Response Database (GERDA) were reviewed to identify characteristics that contributed to successful programs in 45 countries between 1912 and 2013. The most successful treatment (94%) was tissue culture, often in combination with thermotherapy to eradicate viral or bacterial pathogens from plants held in in germplasm collections. Whilst 6% of these programs had no reported outcome, there were no recorded failures of this strategy. Host removal and/or destruction was successful in 55% of the programs and was used against all the pathogen groups. The analysis was limited by the high percentage of unknown outcome results across the pathogen groups. A quarter (49 of 190) of the records contained no indication of the eradication treatment: in 43% of these cases an unknown treatment resulted in successful eradication. There were no obvious correlations between the characteristics of a pathogen (viral/viroid, bacterial/phytoplasma, fungal/oomycete or nematode) and the outcome of the eradication program. For many species there is only one record, or the taxa records were dominated by a few genera that do not represent the biological diversity of the pathogen group. No economic or other analysis was possible due to the large number of unknown result/ongoing programs and the lack of common data. Despite these limitations, GERDA is an important record of the outcomes of worldwide plant pathogen eradication programs since the second decade of the twentieth century. However, care should be exercised when extrapolating from these records to formulating responses to new taxa as pathogens emerge and/or adapt to new plant hosts as the biology of plant pathogens is extremely variable and this diversity is not represented by the records in the database.

The Global Eradication Database documents 811 eradication attempts against invasive arthropods since 1890, in 104 countries. Eradication programs show a greater than exponential increase in the number of programs started in recent decades. In addition, there is a trend of a rapidly diversifying burden of the most severe threats. The species richness showed a three-fold increase in number of species under eradication in the last 50 yr, and all taxonomic levels rose dramatically. The increase in number of eradication programs shows that current management measures for constraining the spread of invasive species are inadequate. A similar surge in the number of governments trying to prevent the establishment of new pests has occurred. Increased biodiversity of arthropod eradication targets includes new pest groups with fewer tools developed for management. We argue that a rapid increase in biodiversity of invasive and economically or environmentally damaging organisms represents a substantial and underestimated challenge for managers wanting to prevent their establishment, requiring a shift in research focus to accelerate delimitation and suppression options with less reliance on insecticides.

The Moroccan ecotype of the braconid parasitoid Microctonus aethiopoides was introduced into New Zealand for biological control of the lucerne pest Sitona discoideus . The parasitoid also attacks several non-target native weevil species found in pasture and also to a lesser extent in native tussock grassland. We carried out a series of laboratory and field experiments, and population modelling to investigate whether the parasitoids were established at low levels on native weevils in tussock grassland, whether S . discoideus was able to survive and support parasitoid development away from lucerne, its normal host plant, or whether parasitism was occurring as a result of spillover from agricultural environments. We found that S. discoideus was able to survive and support parasitoid development on white clover which is commonly found in native grassland. However, the levels of parasitism in weevil species in tussock grassland appeared to be constrained, at least in part, by low temperatures limiting the number of parasitoid generations possible per year and by the frequency of sub-zero temperatures that caused pupal mortality. Projected climate change might reduce this constraint and the implications of this are discussed.

Eradication is the deliberate elimination of a species from an area. Given that international quarantine measures can never be 100% effective, surveillance for newly arrived populations of nonnative species coupled with their eradication represents an important strategy for excluding potentially damaging insect species. Historically, eradication efforts have not always been successful and have sometimes been met with public opposition. But new developments in our understanding of the dynamics of low-density populations, the availability of highly effective treatment tactics, and bioeconomic analyses of eradication strategies offer new opportunities for developing more effective surveillance and eradication programs. A key component that connects these new developments is the harnessing of Allee effects, which naturally promote localized species extinction. Here we review these developments and suggest how research might enhance eradication strategies.

In February 2015 an established population of the Queensland fruit fly (Qfly Bactrocera tryoni) was detected in Grey Lynn Auckland It was questionable whether Qfly might successfully overwinter in Auckland and how trap efficacy and mating behaviour would be affected by winter conditions During the official biosecurity response to eradicate Qfly these questions were addressed using published Qfly models that had been developed and parameterised from biological data from its native range A model for cold acclimatisation suggested that Auckland winters would not be sufficiently cold to cause significant mortality of adult Qfly but substantial cold mortality might occur in more southern locations The temperature requirement for mating suggested mating would be relatively rare from June to October and two models for relative trap efficacy suggested that traps would be relatively ineffective until late spring (OctoberNovember) The Ministry for Primary Industrys biosecurity response was successful with no detection of Qfly after March 2015 and eradication formally declared in December 2015

Sitona obsoletus is a serious pasture pest in New Zealand where its root-feeding larvae reduce white clover cover and nitrogen fixation. To maintain production, farmers may compensate by increasing inputs. The parasitic wasp Microctonus aethiopoides Loan was introduced for biological control of S. obsoletus and achieved parasitism rates exceeding 70%. In Southland, where S. obsoletus was first detected in 2010, unusually severe and prolonged infestations during 2013 and 2014 prompted intensive biological control releases in 2014 and 2015. This study evaluated if they were cost effective in 2015. On dairy farms biological control returned $14.78/ha/year or $2.3 million over the 158,017 ha. On sheep and beef farms, the estimated return was $6.86/ha/year or $4.7 million over 719,854 ha. Monte Carlo simulations were used to estimate returns ($/ha/year) using plausible ranges of model parameter values, and returns were positive in at least 97.5% of simulations. Biological control of S. obsoletus has returned a net benefit in Southland.

Tephritid fruit flies have been comparatively well studied because of the damage they cause to horticultural crops in affected countries New Zealand benefits from this knowledge as it continues to exclude economically damaging fruit fly species For example fruit fly development models are used for biosecurity risk analysis and decision making during incursion responses Here the literature was searched for development times for three species of particular concern to New Zealand the Mediterranean fruit fly the Queensland fruit fly and the oriental fruit fly The published data were reanalysed to fit development models to the different life stages and the generation time The new models were then compared with previously published models for these species The generation time models were found to give reasonably accurate predictions when validated against published estimates of field voltinism overseas This paper presents the most comprehensive analysis to date of fruit fly development times and degree day models

BACKGROUND The identification of new attractants can present opportunities for developing mass trapping, but standard screening methods are needed to expedite this. We have developed a simple approach based on quantifying trap interference in 4 × 4 trap arrays with different spacings. We discuss results from sex pheromones in Lepidoptera (light brown apple moth, Epiphyas postvittana), Diptera (apple leaf curling midge, Dasineura mali) and Homoptera (citrophilous mealybug, Pseudococcus calceolariae), compared with a kairomone for New Zealand flower thrips (Thrips obscuratus). RESULTS The ratio of catch in corner traps to catch in centre traps was 25:1 at 750 D. mali traps ha−1, and was still ∼5:1 at 16 traps ha−1, suggesting trap interference even at such low trap densities. Trap competition for sex pheromone lures at close spacing (

BACKGROUND: The number of insect eradication programmes is rising in response to globalisation. A database of arthropod and plant pathogen eradications covers 1050 incursion responses, with 928 eradication programmes on 299 pest and disease taxa in 104 countries (global eradication database b3.net.nz/gerda). METHODS: A subset of the database was assembled with 211 eradication or response programmes against 17 species of fruit flies (Tephritidae) in 31 countries, in order to investigate factors affecting the outcome. RESULTS: The failure rate for fruit fly eradication programmes was about 7%, with 0% for Ceratitis capitata (n = 85 programmes) and 0% for two Anastrepha species (n = 12 programmes), but 12% for 13 Bactrocera species (n = 108 programmes). A number of intended eradication programmes against long-established populations were not initiated because of cost and other considerations, or evolved during the planning phase into suppression programmes. Cost was dependent on area, ranged from $US 0.1 million to $US 240 million and averaged about $US 12 million (normalised to $US in 2012). In addition to the routine use of surveillance networks, quarantine and fruit destruction, the key tactics used in eradication programmes were male annihilation, protein bait sprays (which can attract both sexes), fruit destruction and the sterile insect technique. CONCLUSIONS: Eradication success generally required the combination of several tactics applied on an area-wide basis. Because the likelihood of eradication declines with an increase in the area infested, it pays to invest in effective surveillance networks that allow early detection and delimitation while invading populations are small, thereby greatly favouring eradication success. © 2014 Society of Chemical Industry Supporting information may be found in the online version of this article.

Effective surveillance is critical to managing biological invasions via early detection and eradication. The efficiency of surveillance systems may be affected by the spatial arrangement of sample locations. We investigate how the spatial arrangement of sample points, ranging from random to fixed grid arrangements, affects the probability of detecting a target population (survey sensitivity) and the overall cost of detecting and eradicating populations invading over time. For single period surveys, regular sampling patterns outperform the equivalent number of random samples at intermediate sample densities, but only when sample sensitivity is high. Otherwise, sample point arrangement has little effect on survey sensitivity, which can be modelled reasonably accurately using a Poisson approximation. For multiple period surveys, we find little difference in the costs of sample point arrangements for most combinations of parameters tested. However, the costs of different arrangements vary when sampling methods have higher sensitivity and trap densities are low, a situation representative of many real surveillance programs. In particular, our results suggest that dynamic trapping arrangements increase the efficiency of detection when traps are sparse relative to the size of target populations. Also, for the scenarios we considered managers may exercise some freedom in allocating sample point locations. Placing individual traps or samples in perceived higher probability sites at the local scale is unlikely to diminish the probability of detection at the broader scale.

Fruit flies (Family Tephritidae), in particular the Queensland fruit fly (Bactrocera tryoni; QFF), areone of the biggest biosecurity risks for New Zealand horticulture. New Zealand has one of the bestscience-based biosecurity systems in the world, based on years of experience and sound research. Theintroduction of fruit flies to New Zealand is now well managed in commercial fruit imports, but the riskis rising from growing trade and travel and, in the case of QFF, climatic adaptation and spread to moresouthern localities. Smarter solutions are continually needed to manage this increasing risk, and to dealwith such pests when they arrive. We present a brief summary of current and anticipated research aimedat reducing the likelihood of entry into New Zealand and/or minimising the impact for the fruit flyspecies of greatest threat to New Zealand. Research spans risk assessment, pathway risk management,diagnostics, surveillance and eradication.

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.

Despite substantial increases in public awareness and biosecurity systems, introductions of non-native arthropods remain an unwelcomed conse- quence of escalating rates of international trade and travel. Detection of an established but unwanted non- native organism can elicit a range of responses, including implementation of an eradication program. Previous studies have reviewed the concept of erad- ication, but these efforts were largely descriptive and focused on selected case studies. We developed a Global Eradication and Response DAtabase (''GER- DA'') to facilitate an analysis of arthropod eradication programs and determine the factors that influence eradication success and failure. We compiled data from 672 arthropod eradication programs targeting 130 non-native arthropod species implemented in 91 countries between 1890 and 2010. Important compo- nents of successful eradication programs included the size of the infested area, relative detectability of the target species, method of detection, and the primary feeding guild of the target species. The outcome of eradication efforts was not determined by program costs, which were largely driven by the size of the infestation. The availability of taxon-specific control tools appeared to increase the probability of eradica- tion success. We believe GERDA, as an online database, provides an objective repository of infor- mation that will play an invaluable role when future eradication efforts are considered.

Thermal accumulation ('degree day') methods are routinely used to predict plant and insect phenology. Depending on the data available, prediction may involve three separate steps with associated errors: estimating daily heat units from maximum and minimum temperatures; interpolating daily maxima and minima from monthly averages; and predicting future monthly averages from past climate, potentially including climate change. This research investigated the potential error in thermal accumulation totals arising from each of these factors at nine New Zealand sites. Ten simple heat unit calculations were tested, including two little-known and three new methods. Those utilising the true daily mean temperature performed best, followed by 4-step, triangle and sine approximations. Interpolating between monthly mean temperature extremes introduced much error into daily estimates, and the use of predicted, rather than observed, monthly normals further increased error. Speciic recommendations are made for thermal accumulation methods depending on what temperature data are available.

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.

Cost-effective surveillance strategies are needed for efficient responses to biological invasions and must account for the trade-offs between surveillance effort and management costs. Less surveillance may allow greater population growth and spread prior to detection, thereby increasing the costs of damages and control. In addition, surveillance strategies are usually applied in environments under continual invasion pressure where the number, size and location of established populations are unknown prior to detection. We develop a novel modeling framework that accounts for these features of the decision and invasion environment and determines the long term sampling effort that minimises the total expected costs of new invasions. The optimal solution depends on population establishment and growth rates, sample sensitivity, and sample, eradication, and damage costs. We demonstrate how to optimise surveillance systems under budgetary constraints and find that accounting for spatial heterogeneity in sampling costs and establishment rates can greatly reduce management costs.

Real-time remote diagnostic tools may help to overcome the “taxonomic impediment” of dwindling and geographically fragmented taxonomic expertise. We tested several real-time remote microscopy systems based on desktop videoconferencing or virtual research environments (VREs) using standardized performance tests and real diagnostic challenges. All performed well, but ease of use was greatest for those systems with a dedicated audio channel, a remote pointer, and control over image quality. The greatest impediment to implementation was the need to overcome internet firewall restrictions. We also implemented a remote specimen viewing system for the New Zealand Arthropod Collection, and compared its performance and cost with that of the conventional specimen loan system. Successful real-time remote identifications were made on a wide variety of arthropod taxa, and there were major benefits: specimen access was more timely, operational costs were lowered, and the risk of specimen damage was reduced. Widespread ...

Insect pheromone traps are becoming an increasingly important tool in biosecurity and pest surveillance, alerting managers to the presence of unwanted organisms. To expand the role of these traps beyond their present sentinel role, it is necessary to develop reliable operational models of local insect dispersal. Following the detection of an insect incursion using a pheromone trap, such models could simulate the dispersal of the insect from its emergence site to the point of detection, enabling biosecurity managers to estimate the most likely proximal source of the incursion. An individual-based moth movement model was developed to simulate observed patterns of moth movement in response to the presence or absence of a pheromone. Using parameters derived from a genetic algorithm, it was possible to fit a model based on the three behavioural components (upwind, upwind with zigzags and casting) described in insect anemotaxis theory to a subset of observed movement patterns (0–135° to the wind), but not to the whole spectrum of movement patterns. It appears that current insect anemotaxis theory is missing a downwind flight component. Whilst the frequency of downwind movements is small; their ground speed could lead to significant downwind displacement, having a disproportionately strong influence on a moth movement model, and hence projections of the likely source or target locations.

A biosecurity response was triggered by the detection of Aedes albopictus (Skuse) (Diptera: Culicidae) at the Port of Auckland, New Zealand, Ae. albopictus does not occur in New Zealand and is the most significant mosquito threat to this country, The possibility that a founding population had established, resulted in a large-scale biosecurity surveillance and control program. The response was initiated in early March 2007 and completed by mid-May 2007. No further exotic mosquitoes were detected, The response surveillance program consisted of larval habitat surveys and high density ovi- and light trapping. It was coordinated with a habitat modification and S-methoprene treatment control program, The response policies were guided by analysis of surveillance and quality assurance data, population modeling, and trace-back activities. Mosquito habitat and activity close to port were both more abundant than expected, particularly in storm water drain sumps, Sumps are difficult to treat, and during the ...

There has been considerable debate on risks associated with biological control, and partly resulting from this, research has addressed a number of questions which have subsequently led to a greater understanding of risk assessment and biosafety. Controversy which arose in the 1980s about the environmental safety of biological control initially created considerable tension between biological control practitioners and those concerned about non-target impacts. Several factors have helped to ease this pressure, and a substantial body of research has addressed many of the questions raised. This has led to advances in quarantine laboratory host range testing to improve our ability to predict post-release impacts. Furthermore, pre- and post-release studies are increasingly involving population models to estimate the population impact of introduced biological control agents rather than simply measuring attack rates. Regulators making decisions about biological control agent introductions work under conditions of considerable uncertainty, but with accumulating data from past introductions to validate earlier decisions, and a robust peer review system for assessing new proposals, there is cause for some optimism that the risks associated with biological control can be better identified and managed in the future. Progress in research and regulation of biological control are discussed with particular reference to Australasia.

Modern biological control practitioners must increasingly demonstrate a level of rigor that can only be achieved through use of effective methodological tools such as modeling, behavioral studies and molecular approaches. The use of these technologies is maturing rapidly in biological control and makes tangible contributions to its success. Behavioral studies often uncover important aspects of biology that would otherwise be overlooked, such as the influence of pre-release handling on establishment success and the response of natural enemies to host-induced plant volatiles. Molecular approaches allow the identification and detection of genetically distinct populations of invasive pest species and their natural enemies, tracing the origin of invasive pest populations and compatible natural enemies, and development of improved recombinant natural enemies. Modeling enables theory and empirical observation to optimize agent selection and release, and to predict quantitative impacts on target and non-target populations. All three methodologies, particularly in combination, contribute to our understanding of the reasons for success and failure in biological control, and together with post-release validation studies build the foundations to improve the success of future biological control releases.

International audience; Modelling moth dispersal in relation to wind direction and strength could greatly enhance the role of pheromone traps in biosecurity and pest management applications. Anemotaxis theory, which describes moth behaviour in the presence of a pheromone plume and is used as a framework for such models. Currently, however, that theory includes only three components: upwind, zigzagging, and sideways casting behaviour. We test anemotaxis theory by analysing the data from a series of mark– release–recapture experiments where the wind direction was known and the insects were trapped using an irregular grid of pheromone traps. The trapping results provide evidence of a downwind component to the flight patterns of the released insects. This active or passive downwind dispersal is likely to be an appetitive behaviour, occurring prior to the elicitation of pheromone-oriented flight patterns (pheromone anemotaxis). Given the potential for significant displacement during down-wind dispersal, this component will have impact on final trap captures and should be considered when constructing moth dispersal models.

We reconstructed the invasion of a non-native tree (hawthorn, Crataegus monogyna) into fire-induced grassland in montane South Island, New Zealand. Using the relationship between height and age to reconstruct the rate of increase of the population, we identified three distinct invasion phases. We hypothesised that these related to the abundance of woody vegetation and therefore of non-native blackbirds (Turdus merula), the primary disperser of hawthorn in this environment. From the 1930s to 1959, increase was relatively slow, with hawthorn spread probably constrained due to browsing of seedlings by European rabbits (Oryctolagus cuniculus) and the low abundance of a native N-fixing shrub (matagouri, Discaria toumatou) providing few perches and nesting sites for blackbirds and safe sites for hawthorn establishment. Subsequently, from 1959 to 1976, hawthorn showed greater than six fold acceleration in its rate of population increase, resulting largely from intensive rabbit control, less frequent fires, and aerial topdressing of phosphate fertilizer promoting the growth of matagouri scrub. In addition, maturing hawthorn trees provided additional food and nesting sites for blackbirds. Hawthorn population increase slowed again from 1976, possibly because most suitable habitat in the immediate vicinity of the population neared saturation. From this case study we have constructed a general hypothesis for the factors determining the rate of invasion of matagouri—grassland habitats by bird-dispersed non-native woody plants in montane New Zealand.

Hawthorn (Crataegus monogyna), a bird-dispersed, introduced shrub, is becoming increasingly weedy in parts of New Zealand, North America, Australia and elsewhere. In order to identify areas threatened by this species, an eco-climatic model for its potential global distribution was constructed using CLIMEX software. The model was based on the native range of hawthorn in Europe and validated against the invaded range elsewhere in the world. It suggests that hawthorn could potentially invade most lowland and montane areas of New Zealand. In lowland areas, invasion is likely to be limited by grazing pressure, but changes in the management of South Island montane grasslands as a result of the current tenure review process may favour hawthorn invasion in some areas. Pre-emptive action to identify and remove infestations from montane grasslands is recommended.

We explore models for the management of invertebrate pests by enhancing the efficacy or local abundance of existing natural enemies. Different aspects of natural enemy biology had different effects on prey density. Enhancement of enemy search rate or prey conversion efficiency showed the greatest potential for reducing prey density, while maximum consumption rate by predators, and parasitoid fecundity, had less effect. The effect on prey density of increased natural enemy longevity depended on its interaction with other parameters. The degree of manipulation needed to achieve a given reduction in prey populations was largely determined by the enemy's potential reproductive rate. Spatial ‘‘attraction’’ of enemies to a target site had an almost linear effect on local prey density. We conclude that successful conservation biological control benefits from a directed approach, targeting the most important aspects of natural enemy ecology, and that there is considerable potential for further research in this area.

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Work to date on biological invasions and the spread of biological control agents has been focused on the explicitly spatial aspects, such as rate of spread and shape of the wave front. There has been relatively little attention paid to the influence of dispersal on the rate of increase of local populations. We use a simple general model for logistic local growth and one-dimensional diffusive dispersal to show that dispersal can act as a substantial drain on local populations. Local increase at a site of introduction is always slower than would be expected in the absence of dispersal, while the rate of increase of other populations is initially enhanced, then reduced by dispersal. This may have an important effect when estimating population parameters for invading organisms or biological control agents during the initial stages of their spread, and helps explain the “latent period” typically observed in biological invasions.

1 The sterile insect technique (SIT) involves the release of large numbers of sterile or partially-sterile insects into a wild pest population to dilute the number of successful wild matings, with the eventual aim of eradication or area-wide suppression. General population models, encompassing a wide range of SIT types, were used to derive principles for optimizing the success of SIT, with particular emphasis on the application of partial sterility leading to inherited sterility in the F1 population. 2 The models show that inherited sterility can only be guaranteed to be more effective than complete sterility if matings between irradiated-lineage partners are unsuccessful. This is widely assumed but rarely examined experimentally. 3 The models allow the critical overflooding ratio, φc, to be calculated for a particular target species, suggesting the release rate required to prevent population increase. Successful eradication using SIT alone should aim for a substantially higher release rate than suggested by φc. 4 The models show that pest populations may continue to increase in the first few generations of SIT releases, regardless of release rate, as irradiated-lineage individuals infiltrate the population. This does not necessarily imply that the SIT programme will be unsuccessful in the longer term. 5For pests with overlapping generations, the models suggest that frequent small releases may be more effective than less frequent large releases, particularly when the average release rate is close to the critical threshold for success.

1. A possible explanation for low success rates when introducing natural enemies to new regions for biological control of insect pests is that they fail to adapt to their new conditions. Therefore it has been widely recommended that biological control practitioners increase the probability of local adaptation by maximizing the genetic variation released. An alternative recommendation is to use climate matching to identify native populations that may already possess traits suited to the new region. However, support for these recommendations is weak through lack of empirical evidence that local adaptation is important to biological control. 2. This study examined how genetic drift and selection influenced the population frequencies of two asexually reproducing, genetically differentiated parasitoid biotypes that were introduced to New Zealand from South America for biological control. Other than by mutation, the biotypes were genetically fixed due to the absence of recombination both within and between biotypes. This meant that adaptive evolution could occur only if selection acted on any traits that varied between the biotypes introduced from South America. 3. The two parasitoid biotypes were released simultaneously at 14 sites and their frequencies were monitored for up to 10 years. Changes in biotype frequency were consistent with strong directional selection favouring one of the South American biotypes, thus generating established parasitoid populations that were better adapted to New Zealand conditions than those that had originally been released. This local adaptation of the control agent contributed to greater mortality of the pest. 4. Synthesis and applications. This study provides the first clear demonstration of the importance of releasing natural enemy genetic variation in new regions to foster adaptive evolution and improve success rates in classical biological control. However, the benefit to biological control of maximizing the genetic variation released needs to be balanced against possible risks to non-target species. The results do not support the concept of choosing sampling sites for putative biological control agents based solely on climatic similarities between the source location and the intended region of introduction.

A cohort-based model for the seasonal phenology of the black-headed strain of the fall webworm, Hyphantria cunea (Lepidoptera: Arctiidae), was constructed from published development rates for each life stage. Model predictions were successfully verified against field observations from Japan, China, Italy, Serbia and the USA. The model was then used to predict phenology in New Zealand, and the potential for establishment near major ports. Populations are predicted to be bivoltine in the north and univoltine in central areas, but are unlikely to form self-sustaining populations south of Timaru. Fall webworm demonstrated the ability to adapt to specific local conditions after its invasion of Japan, so the risk may be greater than these results suggest. Successful validation of the model means that it could be used to inform surveillance and control operations targeting fall webworm outbreaks overseas and potential invasions into new ranges such as New Zealand.

Sitona lepidus had spread throughout the North Island of New Zealand by 2005 and was first detected in the South Island in January 2006 when one individual was found at Harewood Christchurch Intensive sampling during February 2006 recovered only two additional specimens Several specimens were recovered from a separate Christchurch location in August 2006 Localised S lepidus populations were discovered near Richmond Nelson in April 2006 and in Rai Valley in May 2006 A website established in May 2006 to provide information about S lepidus was visited a mean of 135 times per month but it was never used to report possible new South Island infestations A biological control agent Microctonus aethiopoides was released at Richmond and Rai Valley between August 2006 and March 2007 By May 2007 it was parasitising from 4 to 14 of S lepidus adults which indicates it is likely to become permanently established

Currently there are some 187 plant species, almost all exotic in origin, occurring as “weeds” in pastures in New Zealand. Judging from their occurrence in scientific papers published in the proceedings of the New Zealand Plant Protection Society, 65 of these species are, or have been considered historically, to be significant pastoral weeds. While 34 of these pastoral weeds are currently being managed under Regional Pest Management Strategies, 15 of these regionally managed species are apparently un‐researched in New Zealand, implying that their management does not have a scientific basis. The aggregate cost of pastoral weeds to the New Zealand economy is estimated to be NZ$1.2 billion per annum, based on an analysis made in 1984, but this analysis is hampered by a lack of both objective data on the impacts of weeds on pastoral production and an accurate and comprehensive national census of the main problem species. Ongoing naturalisations, from an existing pool of exotic plant species estimated ...

Although the painted apple moth (PAM) eradication programme in West Auckland appears to have been successful the large volume of trade from Australia PAMs native range makes reinvasion likely Recent work has focused on modelling the spatial and temporal effects of optimal release strategies in the sterile insect technique (SIT) programme to enable assessment of the time required and likelihood of eradication success However the costeffectiveness of each strategy is not known Based on the rearing and operational costs from the past PAM SIT release programme the unit cost of a single irradiated male moth for a release programme has been quantified A simple economic model for cost analyses and comparison of a few selected SIT release strategies at ge;95 confidence level of eradication success is presented This model could be used to select an appropriate costeffective strategy thus aiding in prompt decisionmaking of PAM reincursion responses

Key developmental parameters, including the lower threshold temperature for development and thermal accumulation requirements, of T. anartoides reared on an artificial diet were determined. The median number of days required to complete development was measured for each life stage at constant mean temperatures of 6.7, 10.2, 12.6, 17.7, 21.9, 22.5 and 30°C. Rate of development was a linear function of temperature over a range that can be realistically expected in New Zealand, and minimum rates of development were estimated by extrapolation. Eggs failed to emerge at temperatures below 10.2°C. Some neonate larvae survived for 60 days at 6.7°C, but failed to develop. At higher temperatures, larvae usually developed through 4 and 5 instars to males and females respectively, with generation developmental times of 71 and 76 days at 17.7°C, and 33 and 34 days at 30°C (for males and females respectively). Optimum temperatures for development lay between 17.7 and 22.5°C. Female developmental requirements above a ba...

A set of assumptions can be used to estimate the confidence that a continuing lack of detection reflects successful eradication of a pest population This approach is applied to the painted apple moth (Teia anartoides) in Auckland New Zealand based on its known population biology and sterile insect recapture results The analysis suggests that it is extremely unlikely that any wild population might have survived near the core trapping areas beyond mid January 2004 but that there was a significant chance that a small wild population could have remained undetected until then in less intensively trapped areas The moth trapped in Mt Eden in January 2004 plausibly indicates an undetected population there but a continued lack of trap catches over the subsequent year suggests that it is very unlikely that any wild populations now remain undetected within the trapping grid This analysis could be easily adapted for other species targeted for eradication

We measured some aspects of the population ecology of an arboreal aphid, Paradoxaphis plagianthi, that might contribute to its rarity. Models were fitted to data on the development rate and variability of solitary aphids in the laboratory, from larviposition to maturity, which were similar to those of several common European tree‐dwelling aphids. Life tables suggested that the intrinsic rate of population increase increases linearly with temperature to a maximum of 0.123/day at 20°C. Aphid colonies raised in controlled environments showed a lower rate of increase, presumably due to crowding effects. The rate of increase of field colonies was further depressed, probably reflecting the action of other background mortality factors. New data for seasonal population trends in the field matched previously published results, showing an increase in spring followed by a rapid decline and low summer populations. A caging experiment failed to detect any differences in host suitability in late spring between...