The invasive hornet Vespa velutina affects pollination of a wild plant through changes in abundance and behaviour of floral visitors

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.

Quantifying the impact of an invasive Hornet on Bombus terrestris Colonies

The invasive hornet Vespa velutina nigrithorax is considered a proliferating threat to pollinators in Europe and Asia. While the impact of this species on managed honey bees is well-documented, effects upon other pollinator populations remain poorly understood. Nonetheless, dietary analyses indicate that the hornets consume a diversity of prey, fuelling concerns for at-risk taxa. Here, we quantify the impact of V. velutina upon standardised commercially-reared colonies of the European bumblebee, Bombus terrestris terrestris. Using a landscape-scale experimental design, we deploy colonies across a gradient of local V. velutina densities, utilising automated tracking to non-invasively observe bee and hornet behaviour, and quantify subsequent effects upon colony outcomes. Our results demonstrate that hornets frequently hunt at B. terrestris colonies, being preferentially attracted to those with high foraging traffic, and engaging in repeated-yet entirely unsuccessful-predation attempts at nest entrances. Notably however, we show that B. terrestris colony weights are negatively associated with local V. velutina densities, indicating potential indirect effects upon colony growth. Taken together, these findings provide the first empirical insight into impacts on bumblebees at the colony level, and inform future mitigation efforts for wild and managed pollinators.

Convivina is a specialised core gut symbiont of the invasive hornet Vespa velutina

We provide a culturomics analysis of the cultivable bacterial communities of the crop, midgut and hindgut compartments, as well as the ovaries, of the invasive insect Vespa velutina, along with a cultivation-independent analysis of samples of the same nest through 16S rRNA amplicon sequencing. The Vespa velutina bacterial symbiont community was dominated by the genera Convivina, Fructobacillus, Lactiplantibacillus, Lactococcus, Sphingomonas and Spiroplasma. Lactococcus lactis and Lactiplantibacillus plantarum represented generalist core lactic acid bacteria (LAB) symbionts, while Convivina species and Fructobacillus fructosus represented highly specialised core LAB symbionts with strongly reduced genome sizes. Sphingomonas and Spiroplasma were the only non-LAB core symbionts but were not isolated. Convivina bacteria were particularly enriched in the hornet crop and included Convivina intestini, a species adapted towards amino acid metabolism, and Convivina praedatoris sp. nov. which was adapted towards carbohydrate metabolism.

Describing the Pollen Content in the Gastrointestinal Tract of Vespa velutina Larvae

Vespa velutina is an invasive species that exhibits flexible social behavior, which may have contributed to its introduction in several European countries. It is important to understand its behavior in order to combat the effects of its introduction in different areas. This implies knowing the resources that it uses during its biological cycle. Hornets require protein resources taken from insects and organic matter as well as carbohydrates as an energy source to fly and also to forage for food and nest-building materials. The gastrointestinal tract of adults and larvae contains a wide variety of pollen types. The identification of this pollen in larvae collected from nests could offer information about the plant species that V. velutina visits as a foraging place. The main objective of this research was to study the pollen content in the gastrointestinal tract of larvae. Patterns of pollen content and pollen diversity were established according to the nest type, altitude, season, and location in the nest comb. The abundance of pollen types such as Eucalyptus, Castanea, Foeniculum vulgare, Hedera helix, Taraxacum officinale, Echium, or Cytisus pollen type stands out in many of the samples.

Efficacy of Protein Baits with Fipronil to Control Vespa velutina nigrithorax (Lepeletier, 1836) in Apiaries

The yellow-legged hornet (Vespa velutina nigrithorax), outside its natural range, has become a major threat to domestic bees. Several control methods have been used to fight against V. velutina, but the results achieved are not satisfactory. The use of protein baits with biocides has shown to be an effective method to control invasive wasp populations, but they have not been used to control V. velutina. Thus, the efficacy of protein baits containing fipronil to reduce the presence of hornets in apiaries was evaluated in this study. After laboratory determination of the optimal efficacy of a protein bait at a 0.01% concentration of fipronil, field trials were conducted involving 222 beekeepers. The data reported by the 90 beekeepers who completed the requested questionnaire demonstrated that in the groups of apiaries with the highest pressure of hornets (groups with 10-30 and >30 hornets), there was a significant decrease in the presence of V. velutina, lasting at least two weeks. The reduction in the number of hornets was positively correlated with bait consumption, and bait consumption was positively correlated with the number of hornets present at the time of treatment. Although the method used has shown good efficacy and the concentration of fipronil used was very low; possible negative effects on the environment should also be evaluated.

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.

Pesticide contamination in an intensive insect predator of honey bees

Pesticides used for plant protection can indirectly affect target and non-target organisms and are identified as a major cause of insect decline. Depending on species interactions, pesticides can be transferred into the environment from plants to preys and predators. While the transfer of pesticides is often studied through vertebrate and aquatic exposure, arthropod predators of insects may represent valuable bioindicators of environmental exposure to pesticides. A modified QuEChERS extraction coupled with HPLC-MS/MS analysis was used to address the question of the exposure to pesticides of the invasive hornet Vespa velutina, a specialist predator of honey bees. This analytical method allows the accurate quantification of nanogram/gram levels of 42 contaminants in a sample weight that can be obtained from single individuals. Pesticide residues were analyzed in female workers from 24 different hornet nests and 13 different pesticides and 1 synergist, piperonyl butoxide, were identified and quantified. In 75 % of the explored nests, we found at least one compound and in 53 % of the positive samples we could quantify residues ranging from 0.5 to 19.5 ng.g^-1. In this study, hornets from nests located in sub-urban environments were the most contaminated. Pesticide residue analysis in small and easy to collect predatory insects opens new perspectives for the study of environmental contamination and the transfer of pesticides in terrestrial trophic chains.

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.

Effectiveness of electric harps in reducing Vespa velutina predation pressure and consequences for honey bee colony development

BACKGROUND

Vespa velutina has become a species of concern in invaded regions of Europe and Asia, due to its impacts on biodiversity, apiculture and society. This hornet, a ferocious hunter of pollinating insects, poses a serious threat to biodiversity and pollination services. Despite ongoing efforts, its extermination in continental Europe is hampered by a lack of effective control methods, thus effective mitigation measures are primary concerns. The aims of this work were: (i) to study the effects of V. velutina predating on honey bee colonies, and (ii) to assess the effectiveness of electric harps in reducing hunting pressure and predation. We assessed the predation pressure and compared honey bee colony performance, body weight of workers, and winter survivorship for protected versus unprotected colonies in 36 experimental hives across three apiaries.

RESULTS

Electric harps protected honey bees by reducing predation pressure and therefore mitigating foraging paralysis. Consequently, foraging activity, pollen income, brood production and worker body weight were higher in protected colonies which in turn showed greater winter survivorship than those that were unprotected, especially at sites with intermediate to high levels of predation.

CONCLUSION

The predation of V. velutina affects foraging activity, breeding, body weight and colony survivorship of Apis mellifera. Electric harps contribute significantly to mitigate the impact of this invasive hornet on apiaries; however, they should be deployed in tandem with additional measures to preserve honey bee colony stocks, such as facilitating access to food sources for colonies during the periods of highest predation pressure. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Monitoring Study in Honeybee Colonies Stressed by the Invasive Hornet Vespa velutina

Vespa velutina is an invasive species that is currently the main concern for beekeeping in some areas of northern Spain. The hornet hunts honeybees to feed its larvae, stressing and weakening the honeybee colonies. To avoid losses of honeybee colonies, it is essential to investigate the pressure that is exerted by the yellow-legged hornet on apiaries and its consequences. In the present study, hives were monitored in an apiary that was situated in a high-pressure area of V. velutina during the years 2020 and 2021. The monitoring of environmental conditions of the apiary, the internal conditions of the colonies, and a hunting camera were used to relate the presence of hornets in front of the hives to the weather conditions in the apiary and the consequences caused on the colonies. The relationships between weather conditions and the hornet’s activity showed two types of hornet behavior. In the months of July and August, the maximum number of hornets appeared in non-central hours of the day. Meanwhile, in the months of September and October, the highest pressure in the apiary occurred in the central hours of the day, coinciding with temperatures between 15 °C and 25 °C and a relative humidity that was higher than 60%. The honeybee colony with the highest thermoregulatory capacity was the strongest and it was the key factor for the colony survival even when the hornet pressure was high too. Therefore, strengthening the hives and improving beehive health status is essential to avoid colonies decline.

Method for Nest Detection of the Yellow-Legged Hornet in High Density Areas

The Asian hornet Vespa velutina is a social predator that has invaded several countries of Europe and Asia, impacting pollinators, apiculture and human health. One of the few effective control methods developed so far is the early destruction of nests. However, they are often built within dense vegetation, being difficult to detect. The aim of the method described here is to detect nests with a simple procedure, utilizing readily available materials, for widespread use in infested areas. The method has two phases, the first phase involves capturing and marking hornets, lured to a protein bait, and recording the flight directions of individuals to the nest and the time needed to complete a bait-nest-bait round trip, to estimate the distance. Collecting this information from two (or more) bait stations allows to delineate the approximate location of the nest. The second phase aims to determine the precise location of the nest, using sugary baits in the vicinity of the nest and conspicuous marks attached to the released hornets, to visually follow them up to their nest. This method is an alternative to other methods that are either ineffective in areas with high nest density or require expensive equipment and specialized training.

Ensemble evaluation of the potential risk areas of yellow-legged hornet distribution

Invasion of alien species facilitated by climate change and human assistant is one of global threats that cause irreversible damages on the local flora and fauna. One of these issued species, Vespa velutina nigrithorax du Buysson, 1905 (Hymenoptera:Vespidae), is a significant threat to entomofauna, including honeybees, in the introduced regions. This wasp is still expanding its habitats, prioritizing the development of a reliable species distribution model based on recently updated occurrence data. Therefore, the aim of this study was to evaluate the potential areas that are climatically exposed to V. v. nigrithorax invasion globally and in South Korea, where the wasp has caused severe damage to local ecosystems and apiculture after its recent introduction. We developed a new global scale ensemble model based on CLIMEX and Maxent models and applied it to South Korea using field survey data. As a result, risky areas were predicted to be temperate and subtropical climate regions, including the eastern USA, western Europe, Far East Asia, and small areas in South America and Australia. In particular, South Korea has a high potential risk throughout the country. We expect that this study would provide fundamental data for monitoring the environmental risks caused by V. v. nigrithorax using advanced species distribution modeling.

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.

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.