The economic cost of control of the invasive yellow-legged Asian hornet

Ecological integration of Vespa velutina Lepeletier, 1836 in South Korea: a comprehensive study of co-occurrence and interaction patterns with native social wasps

BACKGROUND

The spread of Vespa velutina Lepeletier, 1836 (Asian hornet) in South Korea poses a threat to biodiversity and agriculture. Traditional species interaction models often fail to capture the complexity of invasive species dynamics. This study used association rule learning (ARL) and clustering analyses to explore the interactions of V. velutina with native Vespidae species in South Korea, with the aim of uncovering patterns of coexistence and competition.

RESULTS

Over 4 years (2020-2023), 304 traps were strategically placed across South Korea to collect data on Vespidae species. Our findings showed that Vespula flaviceps, Vespa crabro, and Vespula koreensis were the most frequently encountered species. V. velutina was also widespread, suggesting its successful integration into local ecosystems. The ARL analysis, using the 'apriori' algorithm, identified significant co-occurrence patterns and potential interactions. The rules generated indicated both competitive and coexistent relationships with varying levels of association strength across different regions. Clustering analyses, including hierarchical and k-means clustering, grouped species based on their occurrence similarities. The distinct clusters formed in the analysis highlighted the unique ecological roles and interactions of V. velutina and other Vespidae species in South Korean ecosystems.

CONCLUSION

This study confirms the successful establishment of V. velutina in diverse South Korean ecosystems and highlights its complex interactions with native species. These findings support the need for nuanced management strategies that consider the intricate ecological relationships of V. velutina. This approach is crucial for the effective management of invasive species and ecosystem conservation. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Future range dynamics of Asian yellow-legged hornets (Vespa velutina) and their range overlap with Western honey bees (Apis mellifera) reveal major challenges for bee conservation in Europe

BACKGROUND

The invasion of Asian yellow-legged hornets (Vespa velutina) has significantly affected Western honey bees (Apis mellifera) and apiculture in Europe. However, the range dynamics of this hornet and its range overlap with the bees under future change scenarios have not yet been clarified. Using land-use, climate, and topographical datasets, we projected the range dynamics of this hornet and Western honey bees in Europe and the future overlap of their ranges.

RESULTS

We found that climatic factors had stronger effects on the potential ranges of the hornets compared with land-use and topographical factors. A considerable range expansion of this hornet was predicted, and an increase in the overlap between this pest and the bees was primarily caused by future decreases in temperature seasonality. Additionally, we detected future range expansions of the hornet in the UK and France; future range overlap between this pest and Western honey bees in the UK, Ireland, Portugal, and France; and future overlap between the ranges of this pest and bees but not under recent conditions was mainly projected in Germany, Denmark, and the UK.

CONCLUSION

Mitigating future climate change might effectively control the proliferation of the hornets and their effects on the bees. Strategies for preventing the invasion of this pest and developing European apiculture should be developed and implemented in these regions where future range overlap between them was projected. Given that climate-change scenarios may result in uncertainty in our projections, further investigation is needed to clarify future range changes of our target species. © 2024 Society of Chemical Industry.

VespAI: a deep learning-based system for the detection of invasive hornets

The invasive hornet Vespa velutina nigrithorax is a rapidly proliferating threat to pollinators in Europe and East Asia. To effectively limit its spread, colonies must be detected and destroyed early in the invasion curve, however the current reliance upon visual alerts by the public yields low accuracy. Advances in deep learning offer a potential solution to this, but the application of such technology remains challenging. Here we present VespAI, an automated system for the rapid detection of V. velutina. We leverage a hardware-assisted AI approach, combining a standardised monitoring station with deep YOLOv5s architecture and a ResNet backbone, trained on a bespoke end-to-end pipeline. This enables the system to detect hornets in real-time-achieving a mean precision-recall score of ≥0.99-and send associated image alerts via a compact remote processor. We demonstrate the successful operation of a prototype system in the field, and confirm its suitability for large-scale deployment in future use cases. As such, VespAI has the potential to transform the way that invasive hornets are managed, providing a robust early warning system to prevent ingressions into new regions.

Comparison of Effectiveness and Selectiveness of Baited Traps for the Capture of the Invasive Hornet Vespa velutina

The invasive hornet Vespa velutina affects apiculture, biodiversity, and human health. The use of baited traps with the aim of reducing the population and mitigating its impacts is a common practice. However, the lack of impact on the number of colonies and the high capture rate of non-target insects make it controversial. Our objective was to compare the effectiveness and selectiveness of four trap models. We measured effectiveness as the capture rate of V. velutina per day per trap, and selectiveness as the capture rate of V. velutina/capture rate of non-target species. The E trap had better performance with a higher selectiveness and effectiveness. Traps V and X had a higher effectiveness but the lowest selectiveness, with high capture rates of native insects, including threatened species. The R trap had the lowest effectiveness and selectiveness. Results show that small changes in the design can contribute to achieving more sustainable tools. Otherwise, with the current tools, bait trapping continues to be non-sustainable from an environmental perspective due to the impacts on native biodiversity.

Economic costs of the invasive Yellow-legged hornet on honey bees

Biological invasions have ecological impacts worldwide with potential massive economic costs. Among other ecosystem services such as nitrogen cycle, carbon sequestration and primary production, invasive alien species are particularly known to impact pollination. By predating honey bees (Apis mellifera), the invasive Yellow-legged hornet (Vespa velutina nigrithorax) increases the mortality risk of European bee colonies; however, little is known about its economic costs. We developed an analytic process combining large-scale field data, niche modelling techniques and agent-based models to spatially assess the ecological and economic impacts of the Yellow-legged hornet on honey bees and beekeeping in France. In particular, we estimated (i) the hornet-related risk of bee colony mortality, (ii) the economic cost of colony loss for beekeepers and (iii) the economic impact of livestock replacement compared to honey revenues at regional and national scales. We estimated an overall density of 1.08 hornet nest/km2 in France, based on the field record of 1260 nests over a searched area of 28,348 km2. However, this predator density was heterogeneously spread out across the country as well as the distribution of managed honey bee colonies. Overall, this hornet-related risk of bee colony mortality could reach up to 29.2 % of the beekeepers' livestock at national scale each year in high predation scenario. This national cost could reach as much as € 30.8 million per year due to colony loss, which represents for beekeepers an economic impact of livestock replacement of 26.6 % of honey revenues. Our results suggest non-negligible ecological and economic impacts of the invasive Yellow-legged hornet on honey bees and beekeeping activities. Moreover, this study meets the urgent need for more numerous and accurate economic estimations, necessary to calculate the impact of biological invasions on biodiversity and human goods, with a view to enhance policies of biodiversity conservation.

Invasive alien insects represent a clear but variable threat to biodiversity

Invasive alien insects are an important yet understudied component of the general threat that biological invasions pose to biodiversity. We quantified the breadth and level of this threat by performing environmental impact assessments using a modified version of the Environmental Impact Assessment for Alien Taxa (EICAT) framework. This represents the largest effort to date on quantify the environmental impacts of invasive alien insects. Using a relatively large and taxonomically representative set of insect species that have established non-native populations around the globe, we tested hypotheses on: (1) socioeconomic and (2) taxonomic biases, (3) relationship between range size and impact severity and (4) island susceptibility. Socioeconomic pests had marginally more environmental impact information than non-pests and, as expected, impact information was geographically and taxonomically skewed. Species with larger introduced ranges were more likely, on average, to have the most severe local environmental impacts (i.e. a global maximum impact severity of 'Major'). The island susceptibility hypothesis found no support, and both island and mainland systems experience similar numbers of high severity impacts. These results demonstrate the high variability, both within and across species, in the ways and extents to which invasive insects impact biodiversity, even within the highest profile invaders. However, the environmental impact knowledge base requires greater taxonomic and geographic coverage, so that hypotheses about invasion impact can be developed towards identifying generalities in the biogeography of invasion impacts.

On the Evidence of the European Bee-Eater (Merops apiaster) as a Predator of the Yellow-Legged Hornet (Vespa velutina) and Its Possible Contribution as a Biocontrol Agent

The Yellow-legged Hornet (Vespa velutina nigrithorax) (YLH) is an invasive insect that arrived in Europe in 2004 and is now spread across nine countries. It is a threat to the native entomofauna and harmful to beekeeping and agriculture, as it is a ravenous predator of the European Honey Bee (Apis mellifera) and other pollinating species. Its expansion has been unstoppable and all resources are needed to fight against it, including native vertebrate predators. Among these, the European Bee-eater (Merops apiaster) (EBE) is a potential one, but little is known about its predation on YLH. In a study carried out in Portugal, remains of YHL were detected in EBE nesting sites, which, to the best of our knowledge, is the first such report. This means that this bird could be one more agent in the biological control of this pest (although research on predation intensity is still needed), in conjunction with other natural predators and other strategies. In the Iberian Peninsula, both species are allopatric in vast regions, so the role of EBE may be more limited. However, in the rest of Europe, at a country or continent scale, the scenario may be different and sympatry may occur to a greater extent.

Invasive alien species of policy concerns show widespread patterns of invasion and potential pressure across European ecosystems

Animals, plants, and other organisms unintentionally or deliberately brought into a natural environment where they are not normally found, and where they cause harmful effects on that environment, are known also as invasive alien species (IAS). They represent a major threat to native biodiversity and ecosystem functioning, and can affect negatively human health and the economy. We assessed the presence and potential pressure by IAS on terrestrial and freshwater ecosystems across 27 European countries, for 66 IAS of policy concern. We computed a spatial indicator that accounts for the number of IAS present in an area and the extent of the ecosystems affected; for each ecosystem, we also looked at the pattern of invasions in the different biogeographical regions. We found disproportionally greater invasion in the Atlantic region, followed by Continental and Mediterranean regions, possibly related to historical patterns of first introductions. Urban and freshwater ecosystems were the most invaded (nearly 68% and ca. 52% of their extent respectively), followed by forest and woodland (nearly 44%). The average potential pressure of IAS was greater across cropland and forests, where we also found the lowest coefficient of variation. This assessment can be repeated over time to derive trends and monitor progress towards environmental policy objectives.

Invasion potential of hornets (Hymenoptera: Vespidae: Vespa spp.)

Hornets are large, predatory wasps that have the potential to alter biotic communities and harm honey bee colonies once established in non-native locations. Mated, diapausing females (gynes) can easily be transported to new habitats, where their behavioral flexibility allows them to found colonies using local food and nest materials. Of the 22 species in the genus Vespa, five species are now naturalized far from their endemic populations and another four have been detected either in nature or during inspections at borders of other countries. By far the most likely pathway of long-distance dispersal is the transport of gynes in transoceanic shipments of goods. Thereafter, natural dispersal of gynes in spring and accidental local transport by humans cause shorter-range expansions and contribute to the invasion process. Propagule pressure of hornets is unquantified, although it is likely low but unrelenting. The success of introduced populations is limited by low propagule size and the consequences of genetic founder effects, including the extinction vortex linked to single-locus, complementary sex determination of most hymenopterans. Invasion success is enhanced by climatic similarity between source locality and introduction site, as well as genetic diversity conferred by polyandry in some species. These and other factors that may have influenced the successful establishment of invasive populations of V. velutina, V. tropica, V. bicolor, V. orientalis, and V. crabro are discussed. The highly publicized detections of V. mandarinia in North America and research into its status provide a real-time example of an unfolding hornet invasion.

Climatic Niche Differentiation between the Invasive Hornet Vespa velutina nigrithorax and Two Native Hornets in Europe, Vespa crabro and Vespa orientalis

The introduction and expansion of the Asian yellow-legged hornet (Vespa velutina nigrithorax) in Europe poses concern for multiple reasons, including biodiversity conservation. In addition to the predation of native insects (e.g., bees and wasps), this species may compete with native hornets due to an overlap of their climatic and trophic niches. The aim of this study is to investigate the realised climatic niche of V. v. nigrithorax and its response to climatic conditions and to evaluate the degree of overlap with the niches of the two native Vespa species present in Europe, Vespa crabro and Vespa orientalis. The niches of both native species partially overlap with the niche of the invasive species (Schoener’s D, 0.43 for V. crabro and 0.28 for V. orientalis), although some differences can be detected. V. crabro appears to be more adapted to cold and dry conditions than the invasive species, and V. orientalis is more adapted to arid climates. These differences may provide a competitive advantage to both native species in areas with a lower environmental suitability for V. v. nigrithorax, in the probable event that this species continues to spread, reaching all areas predicted to be suitable in Europe and in the Mediterranean basin.

Automated detection of the yellow-legged hornet (Vespa velutina) using an optical sensor with machine learning

BACKGROUND

The yellow-legged hornet (Vespa velutina) is native to Southeast Asia and is an invasive alien species of concern in many countries. More effective management of populations of V. velutina could be achieved through more widespread and intensive monitoring in the field, however current methods are labor intensive and costly. To address this issue, we have assessed the performance of an optical sensor combined with a machine learning model to classify V. velutina and native wasps/hornets and bees. Our aim is to use the results of the present work as a step towards the development of a monitoring solution for V. velutina in the field.

RESULTS

We recorded a total 935 flights from three bee species: Apis mellifera, Bombus terrestris and Osmia bicornis; and four wasp/hornet species: Polistes dominula, Vespula germanica, Vespa crabro and V. velutina. The machine learning model achieved an average accuracy for species classification of 80.1 ± 13.9% and 74.5 ± 7.0% for V. velutina. V. crabro had the highest level of misclassification, confused mainly with V. velutina and P. dominula. These results were obtained using a 14-value peak and valley feature derived from the wingbeat power spectral density.

CONCLUSION

This study demonstrates that the wingbeat recordings from a flying insect sensor can be used with machine learning methods to differentiate V. velutina from six other Hymenoptera species in the laboratory and this knowledge could be used to help develop a tool for use in integrated invasive alien species management programs. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Insights into the prey of Vespa mandarinia (Hymenoptera: Vespidae) in Washington state, obtained from metabarcoding of larval feces

The northern giant hornet, Vespa mandarinia (Hymenoptera: Vespidae), was detected for the first time in North America in 2019. Four nests have since been located and removed in northwestern Washington State as part of an extensive survey and eradication program. This recent introduction into North America has prompted new research on the biology and ecology of V. mandarinia to help inform management strategies. In its native range, V. mandarinia is known to prey on a variety of insects including the economically important honey bee species Apis cerana and Apis mellifera. Although A. cerana has developed defense mechanisms against attack by V. mandarinia, A. mellifera have no such defenses and an entire hive can be quickly destroyed by only a few hornets. In North America the hornet has been observed foraging on paper wasps (Polistes dominula) and honey bees, but little else is known about prey use in its novel range. To address this knowledge gap, we employed a DNA metabarcoding approach to characterize species detected in larval feces collected from 3 of the 4 Washington V. mandarinia nests found to date. Sequences were recovered for 56 species across fourteen orders, of which 36 species were likely prey items and 20 were suspected inquilines. The most frequently detected species were other social Hymenoptera, with Dolichovespula maculata, P. dominula, and A. mellifera present in most samples. All of the species detected, except for A. mellifera, represent new prey records for V. mandarinia, with eight families of insects newly associated with giant hornets. These results suggest that V. mandarinia in Washington preys on an assortment of insects similar to those documented in its native range, and that this new invader has readily incorporated novel species into its foraging and diet.

The suppressive potential of a gene drive in populations of invasive social wasps is currently limited

Social insects are very successful invasive species, and the continued increase of global trade and transportation has exacerbated this problem. The yellow-legged hornet, Vespa velutina nigrithorax (henceforth Asian hornet), is drastically expanding its range in Western Europe. As an apex insect predator, this hornet poses a serious threat to the honey bee industry and endemic pollinators. Current suppression methods have proven too inefficient and expensive to limit its spread. Gene drives might be an effective tool to control this species, but their use has not yet been thoroughly investigated in social insects. Here, we built a model that matches the hornet's life history and modelled the effect of different gene drive scenarios on an established invasive population. To test the broader applicability and sensitivity of the model, we also incorporated the invasive European paper wasp Polistes dominula. We find that, due to the haplodiploidy of social hymenopterans, only a gene drive targeting female fertility is promising for population control. Our results show that although a gene drive can suppress a social wasp population, it can only do so under fairly stringent gene drive-specific conditions. This is due to a combination of two factors: first, the large number of surviving offspring that social wasp colonies produce make it possible that, even with very limited formation of resistance alleles, such alleles can quickly spread and rescue the population. Second, due to social wasp life history, infertile individuals do not compete with fertile ones, allowing fertile individuals to maintain a large population size even when drive alleles are widespread. Nevertheless, continued improvements in gene drive technology may make it a promising method for the control of invasive social insects in the future.

Global economic costs of mammal invasions

Invasive alien mammals cause huge adverse ecological impact on human society and natural ecosystems. Although studies have estimated economic costs of mammal invasions at regional scales, there is lacking the large-scale comprehensive assessment of currency costs for this taxon. Here, we estimated the economic cost of invasive alien mammals on a global scale using the most comprehensive global database compiling economic costs of invasive species (InvaCost). From 1960 to 2021, mammal invasions caused costs (summing damage costs and management costs) of US$ 462.49 billion to the global economy, while the total amount of robust costs reached US$ 52.49 billion. The majority of the total economic costs corresponded to damage costs (90.27 %), while only 7.43 % were related to management cost. Economic costs showed an increasing trend over time. The distribution of costs was uneven among taxonomic groups and regions, with the global total cost highly biasing toward to 5 species (European rabbit, Domestic cat, Black rat, Wild boar and Coypu), and North America reporting much higher costs (60.78 % of total economic costs) than other regions. The total costs were borne by agriculture, environment, authorities stakeholders and other sectors. Geographic and taxonomic biases suggested that total economic costs caused by invasive alien mammals were underestimated. Integrated research efforts are needed to fill in knowledge gaps in the economic costs generated by mammal invasions and to identify the drivers of the economic costs.

Embryo, Relocation and Secondary Nests of the Invasive Species Vespa velutina in Galicia (NW Spain)

Invasive species become established in non-native areas due to their intrinsic characteristics and the ability to adapt to new environments. This work describes the characteristics of the nesting behavior of the invasive yellow-legged hornet (Vespa velutina nigrithorax) in Galicia (Northwest Spain). The first nest was detected in the area in 2012 and after that, the distribution pattern shows a species-invasion curve with slow progress at first but followed by rapid expansion. The nesting places for this hornet differ between the kinds of nests, while embryo nests are mainly found in buildings in spring, secondary nests are observed in vegetation in summer, autumn, and winter. The annual life cycle starts when the queen builds the embryo nests and starts to lay eggs. This leads to the emergence of the first workers, usually small in size, and sometimes a few males. After this stage, large nests called secondary nests are normally observed in most exposed sites. Relocation nests can also be observed; these are nests in the first stage of development presenting adults insects but without brood or meconium. The period of decline is characterized by the emergence of new queens and males, that are distinguishable even in the pupal stage, the appearance of two eggs per cell, and an irregular brood pattern.

Of Fears and Budgets: Strategies of Control in Vespa velutina Invasion and Lessons for Best Management Practices

Implementing management practices for the control of invasive species can be a complex task with multiple dimensions, where the identification of stakeholders and drivers of those practices is of paramount importance. The invasive hornet Vespa velutina has spread across Europe and Asia from its native range in SE Asia in recent years. A common control method is the removal and destruction of its nests on citizens' request to call centers. In this paper we have explored the knowledge and main factors that influence the perceptions of the citizens on the species in an invaded municipality in NW Spain, as well as the management practices of the municipal emergency unit responsible for nest removal activities. Our analysis brings out multiple drivers of management practices that derive both from the citizens' and practitioners' knowledge, and highlights several points of conflict between both stakeholder groups connected to (1) the degree of service provided to the local population, (2) the risk of allergic reactions as a motive to urge removals, or (3) the quality of information provided by mass media. Our results support the crucial importance of environmental education programs that seek to increase the knowledge of the general public about the threats of invasive species. Such programs might be incorporated to implement and optimize management plans of V. velutina by enhancing communication between experts and local population.

Combining surveys and on-line searching volumes to analyze public awareness about invasive alien species: a case study with the invasive Asian yellow-legged hornet (Vespa velutina) in Italy

The Asian yellow-legged hornet (Vespa velutina) has been invading Italy since 2013, and it was subjected to management programs to counter its spread and raise awareness about its impacts. We administered a questionnaire to a sample of 358 beekeepers in Italy, asking them about their sources of information on V. velutina and their perception of its potential impacts and severity, compared to other threats to beekeeping. We also explored Internet searching volumes on Google and Wikipedia about V. velutina, to identify seasonal and long-term trends in public awareness. Workshops, journals or bulletins, the Internet and word-of-mouth with colleagues were the primary sources of information about V. velutina. Internet searches peaked during the activity period of the species and increased over time, with thousands of visits to Wikipedia each month. Beekeepers believed V. velutina to affect beekeeping by predating on honey bees (Apis mellifera), paralyzing foraging, reducing honey availability and depleting the winter cluster. Moreover, V. velutina has been deemed a severe threat to beekeeping, similar to other threats like pesticides and the varroa mite (Varroa destructor). Our findings indicate that beekeepers seem to be aware of the potential impacts of V. velutina in Italy, both within and outside of its invaded area, considering it a major threat to beekeeping. Moreover, citizens seem to have become progressively curious about the species. Information campaigns on the Internet and specialized magazines might be helpful to communicate about the impacts of the species, and the need to develop diffused surveillance networks.

Contrasting patterns from two invasion fronts suggest a niche shift of an invasive predator of native bees

Background

The accuracy of predictions of invasive species ranges is dependent on niche similarity between invasive and native populations and on our ability to identify the niche characteristics. With this work we aimed to compare the niche dynamics of two genetically related invasive populations of Vespa velutina (an effective predator of honeybees and wild pollinators), in two distinct climatic regions, one in central Europe and another one in the north-western Iberian Peninsula, and hence to identify uninvaded regions susceptible to invasion.

Methods

Niche dynamics and shifts of V. velutina were assessed by comparing the environmental niches of the native and of the two invasive populations, using climatic, topographic and land use variables. We also ran reciprocal distribution models using different algorithms and records from both native and invasive ranges to compare model predictions and estimate which regions are at a greater risk of being invaded.

Results

An apparent niche shift was detected in the population of the NW of Iberian Peninsula, where the species is living under environmental conditions different from the native niche. In central Europe, large suitable areas remain unoccupied. The fact that both invasive populations are well established, despite occupying environmentally distinct regions indicates that V. velutina has a high ability to successfully invade different environmental envelopes from those existing in its native range. For example, in north-western Iberian Peninsula the species is now thriving out of its native niche limits. Moreover, the large extent of still unoccupied environmental space with similar conditions to those used by the species in its native range suggests that there is still a large area of central and eastern Europe that can be potentially invaded by the species.

The Oriental Hornet (Vespa orientalis L.): a Threat to the Americas?

Invasive alien species generate adverse ecological, economic and social impacts in the invaded area. This is particularly alarming as the establishment of alien species shows no sign of saturation worldwide. Among invasive alien species, social wasps of the Vespidae family are well known to negatively impact the biodiversity and economy in the invaded areas. In 2020, an established population of the Oriental Hornet (Vespa orientalis L.) was detected in central Chile. This finding represents the first successful establishment of an insect of the genus Vespa in South America and rises an alarm about its potential spread in the Americas. Here, we performed an ecological niche modelling approach using Global Biodiversity Information Facility (GBIF) and literature occurrences for V. orientalis and a set of environmental variables, to identify the suitable areas for the species outside its native range. The highest suitability values were predicted mostly in warm temperate regions and some arid regions of the world, with humid subtropical, Mediterranean, semi-arid or desert climates. In the Americas, we identified four main regions as moderately or highly suitable for the oriental hornet: the Gulf of Mexico and some areas in western California in the USA, central west Chile and the north-western region of Argentina. When we complemented GBIF occurrences with data from the literature, the potential areas of invasions became broader. Based on our results, we recommend the implementation of early warning monitoring schemes including citizen science initiatives to prevent the invasion of the oriental hornet.

Managing biological invasions: the cost of inaction

Ecological and socioeconomic impacts from biological invasions are rapidly escalating worldwide. While effective management underpins impact mitigation, such actions are often delayed, insufficient or entirely absent. Presently, management delays emanate from a lack of monetary rationale to invest at early invasion stages, which precludes effective prevention and eradication. Here, we provide such rationale by developing a conceptual model to quantify the cost of inaction, i.e., the additional expenditure due to delayed management, under varying time delays and management efficiencies. Further, we apply the model to management and damage cost data from a relatively data-rich genus (Aedes mosquitoes). Our model demonstrates that rapid management interventions following invasion drastically minimise costs. We also identify key points in time that differentiate among scenarios of timely, delayed and severely delayed management intervention. Any management action during the severely delayed phase results in substantial losses $$( > 50\%$$ ( > 50 % of the potential maximum loss). For Aedes spp., we estimate that the existing management delay of 55 years led to an additional total cost of approximately $ 4.57 billion (14% of the maximum cost), compared to a scenario with management action only seven years prior (< 1% of the maximum cost). Moreover, we estimate that in the absence of management action, long-term losses would have accumulated to US$ 32.31 billion, or more than seven times the observed inaction cost. These results highlight the need for more timely management of invasive alien species—either pre-invasion, or as soon as possible after detection—by demonstrating how early investments rapidly reduce long-term economic impacts.

Comparison of the External Morphology of the Sternal Glands for Hornets in the Genus Vespa

Simple Summary

Hornets are a group of 22 species of highly social wasps in the genus Vespa. These conspicuous insects construct large nests that are maintained by one or more queens and their offspring. Unlike other insects, many species of social wasps have glands on the underside of their abdomen called the van der Vecht and Richards glands. Documented uses for these glands by workers of some hornet species include producing pheromones for nestmate recruitment during group attacks on prey and chemical defense of nests against ants. We confirmed that these glands were present in nine hornet species. To examine differences among species in gland morphology, we used scanning electron microscopy to image the external surface of worker bodies around the glands. Accounting for differences in body size, we found that giant hornets and their close relatives had comparatively larger glands than the other species, some of which had glands that were approximately half as large. Differences among species are best explained by how hornets hunt and not by the likelihood that their nesting habitat increases exposure to ant predation. However, more information about how hornet workers use their sternal glands is necessary to permit further interpretation of their comparative gland morphology.

Abstract

Many social wasps in the speciose subfamilies Polistinae and Vespinae have two sternal glands—the van der Vecht gland and the Richards gland—that are not found in other insects. The presence of these glands has been confirmed in only 6 of 22 hornet species (genus Vespa) and images of their fine structure have not been produced. Here; we characterize the external morphology associated with both glands for workers of nine Vespa species using scanning electron microscopy. All hornets had similar gland configurations; although gland-associated external features differed among species. Scaled for size, glands were equivalently sized for the giant hornets (V. mandarinia and V. soror) and their closest phylogenetic relatives (V. tropica and V. ducalis). Relative size of gland-associated structures was reduced by half for V. simillima; V. velutina; and V. affinis workers. The remaining species (V. crabro and V. analis) had intermediately sized features. Differences among species in external gland structure were best explained by selective pressures related to predatory behavior, rather than defense of nests against ants. However, a lack of information about how Vespa workers use their van der Vecht and Richards glands limits a comparative interpretation of the function of their external gland morphology.

Alientoma, a Dynamic Database for Alien Insects in Greece and Its Use by Citizen Scientists in Mapping Alien Species

Invasive alien species have been increasingly acknowledged as a major threat to native biodiversity and ecosystem services, while their adverse impacts expand to human health, society and the economy on a global scale. Insects represent one of the most numerous alien organismic groups, accounting for about one fifth of their total number. In Greece, a large number of alien insects have been identified, currently reaching 469 species. In recent decades, the contribution of citizen science towards detecting and mapping the distribution of alien insects has been steeply increasing. Addressing the need for up-to-date information on alien species as well as encouraging public participation in scientific research, the Alientoma website-derived from "alien" and the Greek word "entoma", meaning insects, is presented. The website aims towards providing updated information on alien species of insects to the public as well as the scientific community, raising awareness about biological invasions and addressing their distribution and impacts inter alia. By maintaining a dynamic online database alongside a strong social media presence since its launch, Alientoma has attracted individuals mainly from Greece and Cyprus, interacting with the website through a total of 1512 sessions. Alientoma intends to establish a constantly increasing network of citizen scientists and to supplement early detection, monitoring and management efforts to mitigate the adverse impacts of alien insects in Greece.

The potential direct economic impact and private management costs of an invasive alien species: Xylella fastidiosa on Lebanese wine grapes

Since its outbreak in 2013 in Italy, the harmful bacterium Xylella fastidiosa has continued to spread throughout the Euro-Mediterranean basin and, more recently, in the Middle East region. Xylella fastidiosa subsp. fastidiosa is the causal agent of Pierce’s disease on grapevines. At present, this alien subspecies has not been reported in Lebanon but if this biological invader was to spread with no cost-effective and sustainable management, it would put Lebanese vineyards at a certain level of risk. In the absence of an Xylella fastidiosa subsp. fastidiosa outbreak, the gross revenue generated by Lebanese wine growers is estimated as close to US$22 million/year for an average period of 5 years (2015–2019). The potential quantitative economic impacts of an Xylella fastidiosa subsp. fastidiosa outbreak and particularly, the private control costs have not been assessed yet for this country as well as for others which Xylella fastidiosa may invade. Here, we have aimed to estimate the potential direct economic impact on growers’ livelihoods and provide the first estimate of the private management costs that a theoretical Xylella fastidiosa subsp. fastidiosa outbreak in Lebanon would involve. For this purpose, we used a Partial Budget approach at the farm gate. For the country as a whole, we estimated that a hypothetical full spread of Xylella fastidiosa subsp. fastidiosa on Lebanese wine grapes would lead to maximum potential gross revenue losses of almost US$ 11 million for an average recovery period of 4 years, to around US$ 82.44 million for an average grapevine life span period of 30 years in which infected plants are not replaced at all. The first yearly estimated additional management cost is US$853 per potentially infected hectare. For a recovery period of 4 years, the aggregate estimated additional cost would reach US$2374/ha, while the aggregate net change in profit would be US$-4046/ha. Furthermore, additional work will be needed to estimate the public costs of an Xylella fastidiosa subsp. fastidiosa outbreak in Lebanon. The observed costs in this study support the concerned policy makers and stakeholders to implement a set of reduction management options against Xylella fastidiosa subsp. fastidiosa at both national and wine growers’ levels. This re-emerging alien biota should not be neglected in this country. This understanding of the potential direct economic impact of Xylella fastidiosa subsp. fastidiosa and the private management costs can also benefit further larger-scale studies covering other potential infection areas and plant hosts.

Biological invasions in France: Alarming costs and even more alarming knowledge gaps

The ever-increasing number of introduced species profoundly threatens global biodiversity. While the ecological and evolutionary consequences of invasive alien species are receiving increasing attention, their economic impacts have largely remained understudied, especially in France. Here, we aimed at providing a general overview of the monetary losses (damages caused by) and expenditures (management of) associated with invasive alien species in France. This country has a long history of alien species presence, partly due to its long-standing global trade activities, highly developed tourism, and presence of overseas territories in different regions of the globe, resulting in a conservative minimum of 2,750 introduced and invasive alien species. By synthesizing for the first time the monetary losses and expenditures incurred by invasive alien species in Metropolitan France and French overseas territories, we obtained 1,583 cost records for 98 invasive alien species. We found that they caused a conservative total amount ranging between US$ 1,280 million and 11,535 million in costs over the period 1993–2018. We extrapolated costs for species invading France, for which costs were reported in other countries but not in France, which yielded an additional cost ranging from US$ 151 to 3,030 millions. Damage costs were nearly eight times higher than management expenditure. Insects, and in particular the Asian tiger mosquito Aedes albopictus and the yellow fever mosquito Ae. aegypti, totalled very high economic costs, followed by non-graminoid terrestrial flowering and aquatic plants (Ambrosia artemisiifolia, Ludwigia sp. and Lagarosiphon major). Over 90% of alien species currently recorded in France had no costs reported in the literature, resulting in high biases in taxonomic, regional and activity sector coverages. To conclude, we report alarming costs and even more alarming knowledge gaps. Our results should raise awareness of the importance of biosecurity and biosurveillance in France, and beyond, as well as the crucial need for better reporting and documentation of cost data.

Economic costs of invasive alien species across Europe

Biological invasions continue to threaten the stability of ecosystems and societies that are dependent on their services. Whilst the ecological impacts of invasive alien species (IAS) have been widely reported in recent decades, there remains a paucity of information concerning their economic impacts. Europe has strong trade and transport links with the rest of the world, facilitating hundreds of IAS incursions, and largely centralised decision-making frameworks. The present study is the first comprehensive and detailed effort that quantifies the costs of IAS collectively across European countries and examines temporal trends in these data. In addition, the distributions of costs across countries, socioeconomic sectors and taxonomic groups are examined, as are socio-economic correlates of management and damage costs. Total costs of IAS in Europe summed to US$140.20 billion (or €116.61 billion) between 1960 and 2020, with the majority (60%) being damage-related and impacting multiple sectors. Costs were also geographically widespread but dominated by impacts in large western and central European countries, i.e. the UK, Spain, France, and Germany. Human population size, land area, GDP, and tourism were significant predictors of invasion costs, with management costs additionally predicted by numbers of introduced species, research effort and trade. Temporally, invasion costs have increased exponentially through time, with up to US$23.58 billion (€19.64 billion) in 2013, and US$139.56 billion (€116.24 billion) in impacts extrapolated in 2020. Importantly, although these costs are substantial, there remain knowledge gaps on several geographic and taxonomic scales, indicating that these costs are severely underestimated. We, thus, urge increased and improved cost reporting for economic impacts of IAS and coordinated international action to prevent further spread and mitigate impacts of IAS populations.

Economic costs of biological invasions in the United Kingdom

Although the high costs of invasion are frequently cited and are a key motivation for environmental management and policy, synthesised data on invasion costs are scarce. Here, we quantify and examine the monetary costs of biological invasions in the United Kingdom (UK) using a global synthesis of reported invasion costs. Invasive alien species have cost the UK economy between US$6.9 billion and $17.6 billion (£5.4 – £13.7 billion) in reported losses and expenses since 1976. Most costs were reported for the entire UK or Great Britain (97%); country-scale cost reporting for the UK's four constituent countries was scarce. Reports of animal invasions were the costliest ($4.7 billion), then plant ($1.3 billion) and fungal ($206.7 million) invasions. Reported damage costs (i.e. excluding management costs) were higher in terrestrial ($4.8 billion) than aquatic or semi-aquatic environments ($29.8 million), and primarily impacted agriculture ($4.2 billion). Invaders with earlier introduction years accrued significantly higher total invasion costs. Invasion costs have been increasing rapidly since 1976, and have cost the UK economy $157.1 million (£122.1 million) per annum, on average. Published information on specific economic costs included only 42 of 520 invaders reported in the UK and was generally available only for the most intensively studied taxa, with just four species contributing 90% of species-specific costs. Given that many of the invasive species lacking cost data are actively managed and have well-recognised impacts, this suggests that cost information is incomplete and that totals presented here are vast underestimates owing to knowledge gaps. Financial expenditure on managing invasions is a fraction (37%) of the costs incurred through damage from invaders; greater investments in UK invasive species research and management are, therefore, urgently required.

Identification of pathogens in the invasive hornet Vespa velutina and in native Hymenoptera (Apidae, Vespidae) from SW-Europe

Invasive species contribute to deteriorate the health of ecosystems due to their direct effects on native fauna and the local parasite-host dynamics. We studied the potential impact of the invasive hornet Vespa velutina on the European parasite-host system by comparing the patterns of diversity and abundance of pathogens (i.e. Microsporidia: Nosematidae; Euglenozoa: Trypanosomatidae and Apicomplexa: Lipotrophidae) in European V. velutina specimens with those in the native European hornet Vespa crabro, as well as other common Hymenoptera (genera Vespula, Polistes and Bombus). We show that (i) V. velutina harbours most common hymenopteran enteropathogens as well as several new parasitic taxa. (ii) Parasite diversity in V. velutina is most similar to that of V. crabro. (iii) No unambiguous evidence of pathogen release by V. velutina was detected. This evidence together with the extraordinary population densities that V. velutina reaches in Europe (around of 100,000 individuals per km² per year), mean that this invasive species could severely alter the native pathogen-host dynamics either by actively contributing to the dispersal of the parasites and/or by directly interacting with them, which could have unexpected long-term harmful consequences on the native entomofauna.

Six years of controlling the invasive species Vespa velutina in a Mediterranean island: The promising results of an eradication plan

BACKGROUND

The yellow-legged hornet, Vespa velutina nigrithorax, is an invasive alien species (IAS) which was accidentally introduced in Europe from Asia. This social insect preys primarily on honeybees but also on other pollinators and insects. Consequently, the establishment of this pest has a negative impact on biodiversity, pollination and economy. There is no clear coordination and uniformed methods for eradication measures between countries. Here we present the first field study of the strategy of eradication of the pest species V. velutina that has been conducted in the westernmost Mediterranean archipelago.

RESULTS

We investigated the combination of different eradication methods, such as trapping; the use of the citizen science data for detection of presence, the active search of nests and the removal of nests using mechanical methods. The progression of the number of secondary nests found was 1 (2015), 9 (2016) and 20 (2017), with zero during 2018, 2019 and 2020, and just one embryo nest in 2018. More than half of the nests (58%) were detected thanks to citizen science data. The people sent us adult detections, and we started the triangulation method to find the nests. The last hornet found in the traps was in June 2018.

CONCLUSION

Early detections of the IAS are crucial to minimise their effects, and citizen science may offer an important source of information to determine the presence and distribution of V. velutina. The findings we present here indicate successful management for this globally significant pest and could contribute to advance the 'science of eradication'. © 2021 Society of Chemical Industry.

Giants are coming? Predicting the potential spread and impacts of the giant Asian hornet (Vespa mandarinia, Hymenoptera:Vespidae) in the USA

BACKGOUND

Biological invasions are a global concern in agriculture, food production and biodiversity. Among the invasive species, some hornets are known to have serious effects on honey bees, as found during the invasion of Vespa velutina in Europe. The recent findings of Vespa mandarinia individuals in Washington state in the west coast of the USA have raised alarm in the whole country. Here we estimate the potential spread of V. mandarinia in the USA, analyzing its potential impacts on honey bee colonies, economic losses in the honey bee industry and bee-pollinated croplands.

RESULTS

We found that V. mandarinia could colonize Washington and Oregon states in the west coast and a significant proportion of the east coast. If this species spread across the country, it could threaten 95 216 ± 5551 honey bee colonies, threatening an estimated income of US$11.9 and 101.8 million for hive derived products and bee-pollinated crops production, respectively, while colonizing 60 837.8 km² of bee-pollinated croplands.

CONCLUSION

Our results suggest that V. mandarinia will have serious effects in the USA, raising the need for prompt monitoring actions and planning at different administrative levels to avoid its potential spread.

Effectiveness and Selectiveness of Traps and Baits for Catching the Invasive Hornet Vespa velutina

Vespa velutina is an invasive hornet that is colonising several countries worldwide, with detrimental effects on multiple components but primarily affecting honey bees and native insect species. Traps for wasps and hornets are commonly used for trapping V. velutina, both for monitoring and control purposes. In this study, we compared the performances of two typologies of traps and baits widely used for trapping this invasive hornet, by evaluating their effectiveness and selectiveness in trapping V. velutina in two sites during two different periods of the year, spring and autumn. The performance of the traps changed in relation to (i) the trap's model, (ii) the bait's typology and (iii) the period of the year. In spring, traps with common beer as bait were more effective and more selective independently of trap's model than the commercial bait that has been tested. On the contrary, in autumn, just one combination of trap and attractant (the commercial trap and bait) achieved higher effectiveness and selectiveness. Despite the underlined variations among traps and baits, overall catches of V. velutina were scanty compared to bycatches of non-target insects, since best performing traps either in term of effectiveness and selectiveness caught 3.65% of the target species in spring and 1.35% in autumn upon the total trapped insects. This highlights the urgent necessity of developing more selective trapping methods for monitoring and particularly for controlling purposes.

Characterizing thermal tolerance in the invasive yellow-legged hornet (Vespa velutina nigrithorax): The first step toward a green control method

The yellow-legged hornet, Vespa velutina nigrithorax (Hymenoptera: Vespidae, Lepeletier 1836), is native to Southeast Asia and has been unintentionally introduced in France. The species is spreading in many areas of the world. The European Union has classified V. velutina as a species of concern because the hornet significantly affects beekeeping activities, mostly by preying honeybees (Apis mellifera) at beehive entrances. No current control method is simultaneously eco-friendly and effective. Here, we aimed to develop a greener technique for destroying V. velutina nests, inspired by a defense behavior used by the eastern honeybee (Apis cerana), the "heat ball". In the laboratory, we tested how V. velutina of different sexes, castes, and developmental stages responded to different heat exposure systems employing a range of temperature levels. Overall, the time of death decreased as temperature increased. Hornets died faster when the temperature was gradually increased than when it was instantaneously increased; larvae seemed to be more thermally tolerant. The most promising and potential technique for quickly destroying hornet nests may be steam injection, as the humid airflow system killed all hornets within 13 seconds, and therefore could be a good candidate for a green nest control method.