Invasive Alien Species In Europe Research Articles

Marine invasive alien species in Europe: 9 years after the IAS Regulation

Biological invasions, resulting from human activities, exert substantial impacts on ecosystems worldwide. This review focuses on marine invasive alien species (IAS) in Europe, examining the current state, proposing strategies to address the problem, and offering recommendations for enhanced management. Effective management of biological invasions relies on accessible, accurate data to inform decision-making. Information systems such as the European Alien Species Information Network (EASIN), Aquatic Non-Indigenous and Cryptogenic Species (AquaNIS), and World Register of Introduced Marine Species (WriMS) provide comprehensive databases on IAS, but their sustainability requires long-term maintenance, continuous updates, and support. Most countries lack specific monitoring programs for marine IAS, and standardization and improvement of monitoring methods are needed. Port monitoring plays a vital role in the early detection of new arrivals, and recent advancements in molecular techniques show promise for effective IAS monitoring. Risk screening tools are commonly employed to rank taxa based on their invasiveness potential in European regions, but variations in protocols can yield inconsistent results. European impact assessments highlight resource competition, novel habitat creation, and predation as primary mechanisms for negative impacts on biodiversity, while the creation of novel habitats represents a key mechanism for positive impacts. Preventing IAS introductions is critical, and measures such as ballast water treatment systems are implemented to reduce the likelihood of marine introductions. However, understanding introduction pathways remains uncertain for many IAS. Eradication and control efforts for marine IAS have limited success, emphasizing the need for enhanced biosecurity measures. Climate change, especially ocean warming, can intensify IAS impacts on native species and ecosystems. In climate change hotspots, some tropical aliens may, however, compensate for the loss of thermally sensitive natives with similar traits. Therefore, it is imperative to consider the interactions between climate change and IAS in developing effective management and conservation strategies. Enhancing IAS management in Europe entails i) securing adequate funding, ii) expanding the list of IAS of Union Concern to adequately cover marine invasions, iii) learning from countries with successful biosecurity practices, iv) sustaining information systems, v) improving monitoring and early warning systems with innovative technologies, vi) enhancing prediction models, vii) conducting integrated impact assessments and mapping cumulative IAS impacts, and vii) considering the potential benefits of IAS in ecosystem functioning and services.

The hidden threat: Exploring the parasite burden and feeding habits of invasive raccoon dogs (Nyctereutes procyonoides) in central Europe

Originally from Asia, the raccoon dog Nyctereutes procyonoides is an invasive alien species in Europe, listed since 2019 on the List of invasive alien species of Union concern. The raccoon dog is considered to have negative impact on native biodiversity, as well as a crucial role in hosting and transmitting diverse parasites and pathogens of human and veterinary importance. In the present study, stomach content analyses and parasitological examinations were performed on 73 raccoon dogs from Germany. In addition, fecal samples were analyzed. The results of the study confirm the assumption that the examined raccoon dogs were infested with a various ecto- and endoparasite fauna. A total of 9 ecto- and 11 endoparasites were detected, with 6 of the endoparasites having human pathogenic potential. Trichodectes canis (P = 53.42%), Toxocara canis (P = 50.68%) and Uncinaria stenocephala (P = 68.49%) were the most abundant parasite species. The stomach contents consisted of approximately one-third vegetable and two-thirds animal components, composed of various species of amphibians, fish, insects, mammals and birds. Among them were specially protected or endangered species such as the grass frog Rana temporaria. The study shows that the raccoon dog exerts predation pressure on native species due to its omnivorous diet and, as a carrier of various parasites, poses a potential risk of infection to wild, domestic and farm animals and humans.

Helminths in Invasive Raccoons (Procyon lotor) from Southwest Germany.

As hosts of numerous zoonotic pathogens, the role of raccoons needs to be considered in the One Health context. Raccoons progressively expand their range as invasive alien species in Europe. This study aimed to investigate the intestinal helminth fauna of raccoons in Baden-Wuerttemberg, Germany, as no such screening had ever been conducted there. In total, we obtained 102 animals from hunters in 2019 and 2020. Intestinal helminths were retrieved using the SSCT (segmented sedimentation and counting technique) and identified morphologically and by PCR-based Sanger sequencing. Fecal samples were assessed using the ELISA PetChekTM IP assay (IDEXX, Germany) and flotation technique. The artificial digestion method was employed for analyzing muscle tissue. We detected species of four nematode genera (Baylisascaris procyonis, Toxocara canis, Capillaria spp., and Trichuris spp.), three cestode genera (Atriotaenia cf. incisa/procyonis, Taenia martis, and Mesocestoides spp.), and three trematode genera (Isthmiophora hortensis/melis, Plagiorchis muris, and Brachylaima spp.). Echinococcus spp. and Trichinella spp. were not found. The invasive behavior and synanthropic habits of raccoons may increase the infection risk with these helminths in wildlife, domestic and zoo animals, and humans by serving as a connecting link. Therefore, it is crucial to initiate additional studies assessing these risks.

Feral American mink Neogale vison continues to expand its European range: time to harmonise population monitoring and coordinate control

Abstract The American mink Neogale vison is an invasive alien species in Europe that threatens endemic biodiversity and can transmit zoonotic diseases, including the SARS‐CoV‐2 virus. The last attempt to map the geographic range of this species in Europe, at continental scale, dates back to 2007. We aimed to update the distribution map of the feral American mink and assess its temporal trends. The information we collected was critically analysed with the aim of improving future monitoring protocols and data collection. We gathered and standardised data from 34 databases, covering 32 countries. Through 3 five‐year periods from 2007 to 2021, changes in range size, hunting bags and capture statistics were analysed. We also reviewed the current situation of mink farming in the different European countries and recorded population control schemes. The American mink is now widespread in the Baltic States, France, Germany, Iceland, Ireland, Poland, Scandinavia, Spain and the UK. The species is reported to be absent in some areas (e.g. parts of the UK, Iceland and Norway). Data are deficient for several countries, mainly in south‐eastern Europe. These findings indicate that, during the last 15 years, the species has continued to spread across the continent, increasing its potential extent of occurrence in most countries. Our effort to collect and harmonise data across international borders highlighted information gaps and heterogeneity in data quality. Updated distribution data on the species provided here will aid risk assessment and risk management policies. These actions require a coordinated effort for population monitoring at continental level. Monitoring effort and data collection should be intensified in south‐eastern Europe to improve data on the current distribution of this invasive species.

Transmission of Verticillium nonalfalfae via root contact from inoculated Ailanthus altissima in close‐to‐nature conditions

AbstractAilanthus altissima is an invasive alien species in Europe. Biological control of this tree species by Verticillium nonalfalfae is a potential alternative control approach. This study investigates host specificity, pathogenicity and transmission of V. nonalfalfae to neighbouring plants with root contact in mini‐ecosystems. V. nonalfalfae led to dieback of all inoculated Ailanthus trees. Furthermore, V. nonalfalfae was transmitted to neighbouring Ailanthus trees, causing wilt and dieback, and, in one case, to Quercus petraea, which did not display any disease symptoms. Lastly, V. nonalfalfae could not be detected in the soil, which suggests transmission via root contact.

Pilot Application of ‘Invasive Alien Species in Europe’ Smartphone App in the Danube Region

The present pilot study tested and validated the use of the ‘Invasive Alien Species in Europe’ smartphone app (IASapp) in the Lower Danube Region. The study was conducted in three stages: (1) Testing the effectiveness of the app in Bulgaria, Romania and Serbia by organizing information and field testing campaigns; (2) Improving and extending the functionality of the app and developing a list of the invasive alien species (IAS) of concern to the Danube River Basin (DRB); and (3) Testing the updated app during the Joint Danube Survey 4 campaign. Overall, 13 campaigns were carried out, during which seven aquatic IAS of EU concern and nine IAS relevant to the DRB were recorded. Currently, the developed new functionality of IASapp allows the recording of 64 IAS of DRB concern. The updated IASapp has an important role in increasing public awareness on IAS issues, as well as in enlarging the participation and output of citizen science in the IAS early detection, monitoring and reporting in the DRB. Therefore, the constant communication with existing stakeholder groups and establishment of new citizen science groups is crucial for increasing the effectiveness of using the IASapp in the Danube Region and tackling the IAS issues.

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.

Liquid Baits with Oenococcus oeni Increase Captures of Drosophila suzukii.

Simple SummaryAmong the challenges arising from climate change and the transformation of agroecosystems is that agricultural production is heavily affected by invasive insect species. Invasive insects can establish in new areas where their development can progress due to a suitable climate and lack of natural enemies. Farmers have few options to mitigate those insects’ attacks. Current control tactics using pesticides must be replaced with more sustainable methods to counter invasive insect species. We approached the control of the invasive spotted-wing drosophila Drosophila suzukii, using a baiting system that manipulates insect behavior without use of toxic or non-sustainable chemicals. The results of our work are utilized for the monitoring and mass trapping of this devastating invasive species. In our innovative smart-design trap system, we use odors that attract flies and decrease damage in open field scenarios. Our trapping system can efficiently detect the first spring arrival of D. suzukii in agricultural fields and as a such, represents a good early monitoring tool. We conducted four years of laboratory and open-field trials in different berry crops. As a source of odor attraction, we used a mixture of wine, apple cider vinegar, and different commercially available strains of lactic acid bacteria. The spotted-wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), native to Eastern Asia, is an invasive alien species in Europe and the Americas, where it is a severe pest of horticultural crops, including soft fruits and wine grapes. The conventional approach to controlling infestations of SWD involves the use of insecticides, but the frequency of application for population management is undesirable. Consequently, alternative strategies are urgently needed. Effective and improved trapping is important as an early risk detection tool. This study aimed to improve Droskidrink® (DD), a commercially available attractant for SWD. We focused on the chemical and behavioral effects of adding the bacterium Oenococcus oeni (Garvie) to DD and used a new trap design to enhance the effects of attractive lures. We demonstrate that microbial volatile compounds produced by O. oeni are responsible for the increase in the attractiveness of the bait and could be later utilized for the development of a better trapping system. Our results showed that the attractiveness of DD was increased up to two-fold by the addition of commercially available O. oeni when combined with an innovative trap design. The new trap-bait combination increased the number of male and especially female catches at low population densities.

Using structured eradication feasibility assessment to prioritize the management of new and emerging invasive alien species in Europe.

Prioritizing the management of invasive alien species (IAS) is of global importance and within Europe integral to the EU IAS regulation. To prioritize management effectively, the risks posed by IAS need to be assessed, but so too does the feasibility of their management. While the risk of IAS to the EU has been assessed, the feasibility of management has not. We assessed the feasibility of eradicating 60 new (not yet established) and 35 emerging (established with limited distribution) species that pose a threat to the EU, as identified by horizon scanning. The assessment was carried out by 34 experts in invasion management from across Europe, applying the Non-Native Risk Management scheme to defined invasion scenarios and eradication strategies for each species, assessing the feasibility of eradication using seven key risk management criteria. Management priorities were identified by combining scores for risk (derived from horizon scanning) and feasibility of eradication. The results show eradication feasibility score and risk score were not correlated, indicating that risk management criteria evaluate different information than risk assessment. In all, 17 new species were identified as particularly high priorities for eradication should they establish in the future, whereas 14 emerging species were identified as priorities for eradication now. A number of species considered highest priority for eradication were terrestrial vertebrates, a group that has been the focus of a number of eradication attempts in Europe. However, eradication priorities also included a diverse range of other taxa (plants, invertebrates and fish) suggesting there is scope to broaden the taxonomic range of attempted eradication in Europe. We demonstrate that broad scale structured assessments of management feasibility can help prioritize IAS for management. Such frameworks are needed to support evidence-based decision-making.

Comparison of Lateral and Dorsal Recumbency during Endoscope-Assisted Oophorectomy in Mature Pond Sliders (Trachemys scripta).

Simple SummaryOvariectomy via the prefemoral fossa, with or without endoscopic assistance, is a well-described technique for elective and therapeutic sterilization in chelonians. The choice between lateral and dorsal recumbency is generally left to the surgeon’s preference, with no data supporting an objective superiority of one over the other. In pond sliders, common pets but also an invasive alien species in Europe, we compared two different recumbencies (right lateral with a left fossa approach, and dorsal with a right fossa approach) regarding ease of access to the coelomic cavity, ease of identification of the ovary opposite to the surgical breach, first and second ovary removal times, and total surgical time. No significant difference was found between the two groups for any evaluated parameter. Endoscope-assisted prefemoral ovariectomy in mature pond sliders can be indifferently performed in lateral or dorsal recumbency, depending on the preference of the surgeon, on the animal’s pathophysiologic status, or on the necessity to perform concurrent procedures.Ovariectomy via the prefemoral fossa is a well-described technique for sterilization in chelonians. The choice between lateral and dorsal recumbency is generally left to the surgeon’s preference, with no data supporting an objective superiority of one over the other. Twenty-four sexually mature female pond sliders (Trachemys scripta) were enrolled for elective prefemoral endoscope-assisted oophorectomy, and were randomly divided in two groups: 12 animals were placed in right lateral recumbency with a left fossa approach (Group A), and 12 in dorsal recumbency with a right fossa approach (Group B). Scoring systems were applied to assess the ease of access to the coelomic cavity, and the ease of identification of the ovary opposite to the surgical incision. A negative correlation was found between the body weight of the animals and the ease of access to the coelom (p = 0.013), making the access easier in smaller animals. No significant difference was found between the two groups in terms of ease of access to the coelomic cavity, first ovary removal time, ease of identification of the second ovary, second ovary removal time, or total surgery time.

The ability of seeds to float with water currents contributes to the invasion success of Impatiens balfourii and I. glandulifera

Two alien species in Europe, Impatiens glandulifera and I. balfourii, are closely related, have similar growth rates and reproductive capacities, and are very attractive to pollinators. Nevertheless, only I. glandulifera is a highly invasive alien species in Europe, while I. balfourii is non-invasive. We assumed that the varying levels of invasiveness are driven by differences in the floating ability of their seeds, which may determine the invasion success of riparian alien plants, such as the Impatiens species. By mimicking two types of aquatic conditions, we determined seed floating ability for each species from younger and older populations. We also analyzed four seed traits: seed viability, surface, shape and coat structure. Seeds of the non-invasive I. balfourii float less well than seeds of the invasive I. glandulifera. We also found that the seeds of I. balfourii from the younger population have a higher floating ability in comparison with that of the seeds from the older population. The results for I. glandulifera were the opposite, with decreased floating ability in the younger population. These differences were associated with seed surface, shape and coat structure. These results indicate that the floating ability of I. balfourii seeds may increase over time following its introduction into a given area, while in the case of I. glandulifera, this ability may gradually decrease. Therefore, the former species, currently regarded as a poor disperser, has the potential to become invasive in the future, whereas the latter does not seem to benefit from further investments in the floating ability of its seeds.

Assessing invasive alien species in European catchments: Distribution and impacts

Invasive alien species (IAS) induce changes to community structure and functions which lead to a decline of endemic species and major irreversible changes to the local physical habitat. The distribution and the impacts of multiple freshwater IAS are not well known, and they have not been investigated simultaneously at catchment and at European scales.This study provides an assessment of the distribution and cumulative impact of freshwater IAS over European catchments. IAS occurrences were retrieved from the European Alien Species Information Network geospatial dataset and updated with the most recent records from the literature. The Cumulative Impact Index of Invasive Alien Species (CIMPAL) was derived by aggregating the impacts of species and their occupied area at catchment level by following three steps: i) IAS were scored by both the magnitude of impacts on freshwater ecosystems and the strength of evidence in the literature, ii) scores were mapped over the catchment area, and iii) scores were summed across IAS over the catchment. The distribution of CIMPAL in the river ecological classes of the Water Framework Directive was examined and increasing/decreasing patterns identified across ecological statuses.Results showed strong spatial variation in the documented distribution and impacts of IAS in Europe. Catchments with CIMPAL scores >40 (range 0–55) clustered in Western European countries (e.g. Belgium and France) were characterised by plant, invertebrate and vertebrate IAS that had both a large impact in magnitude and colonisation at local (catchment level) and large scale (across catchments). CIMPAL showed statistically significant and increasing values from high to bad ecological classes in eight countries only (Belgium, the Czech Republic, Germany, France, Hungary, Italy, Luxemburg, Poland). This study provides comprehensive evidence of the distribution and impact of IAS within freshwater environments that could be used to improve understanding of the ecological pressures at catchment scale.

Attacks by predators on artificial cryptic and aposematic insect larvae

AbstractColour and colour patterns seem to be especially important visual warning signals for predators, which might have innate or learned ability to avoid aposematic prey. To test the importance of larval colour pattern of the aposematic ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an invasive alien species in Europe, we presented the plasticine models of aposematic larvae to wild and naïve birds. We studied the attacks on aposematic larvae of various patterns and colours in nature and in an outdoor aviary. The larvae were cryptic (green), aposematic (resembling those of the H. axyridis larvae), and semi‐aposematic (i.e., black but missing the typical orange patches of H. axyridis larvae). We detected attacks on 71 larvae out of 450 (i.e., 2.6% daily predation). Twenty‐nine attacks were made by birds, 37 by arthropods, and five by gastropods. Wild birds attacked green and black larvae significantly more often than aposematic larvae. Colour did not have an effect on attacks by arthropods. The experiment with naïve birds was conducted in an outdoor aviary, where naïve great tits, Parus major L., were offered the same artificial larvae as in the first experiment. In total, 57 of 90 exposed larvae were attacked by birds (i.e., 28% daily predation), and green larvae were attacked significantly more than the aposematic larvae (but not more than black larvae). Our results imply that aposematic larvae of H. axyridis are more than 12× less likely to be predated by birds than green larvae in nature. The aposematic pattern represented a more effective signal than the semi‐aposematic signal. The ability to reject aposematic prey seemed to be innate in our birds.

First report of the influence of temperature on the bionomics and population dynamics of Aedes koreicus, a new invasive alien species in Europe

BackgroundAedes koreicus was detected in northern Italy for the first time in 2011, and it is now well established in several areas as a new invasive mosquito species. Data regarding the influence of temperature on mosquito survival and development are not available yet for this species.MethodsWe experimentally investigated the influence of different constant rearing temperatures (between 4 and 33 °C) on the survival rates and developmental times of different life stages of Ae. koreicus under laboratory conditions. The resulting data were subsequently used to inform a mathematical model reproducing the Ae. koreicus life-cycle calibrated to counts of adult females captured in the field in the autonomous province of Trento (northern Italy) between 2016 and 2018.ResultsWe found that temperatures above 28 °C are not optimal for the survival of pupae and adults, whereas temperate conditions of 23–28 °C seem to be very favorable, explaining the recent success of Ae. koreicus at establishing into new specific areas. Our results indicate that Ae. koreicus is less adapted to local climatic conditions compared to Ae. albopictus, another invasive species which has been invading the area for the last three decades. Warmer seasons, which are more likely to occur in the future because of climate change, might extend the breeding time and therefore increase the abundance of Ae. koreicus in the study region.ConclusionsOur findings provide, to our knowledge, the first evidence on how temperature influences the bionomics and dynamics of Ae. koreicus and highlight the need for further studies on the phenology of this species in temperate areas of Europe.

Current and future impacts of nest predation and nest‐site competition by invasive eastern grey squirrels Sciurus carolinensis on European birds

Abstract The eastern grey squirrel (hereafter ‘grey squirrel’) is considered one of the most damaging invasive alien species in Europe, with negative effects on native ecosystems. Despite it being widely perceived as a significant predator of bird eggs and chicks and as a competitor for nest sites, evaluation of the grey squirrel’s impact on European bird populations has been hindered by limited empirical data. The aim was to review the incidence of grey squirrels as nest predators of and nest‐site competitors with European birds, and to use this information to identify species at potential risk of negative effects from within the grey squirrel’s expanding range in continental Europe. A comprehensive literature review was conducted, and the data were used alongside additional new data, to assess nest predation and competition by grey squirrels in their current European range. Bird species were grouped by nest‐site type, which was used to predict the impact on similar species groups in regions of continental Europe predicted to be colonised by grey squirrels in the current century. Camera‐monitoring and field evidence for 12 bird species and 12420 nests in Britain showed that grey squirrels rarely depredated eggs or chicks, affecting just 0.5% of nests. Nest‐site competition was also minor, with grey squirrels occupying 0.8% of 122 small tree cavities and 14% of 57 larger cavities. At least 69 bird species in continental Europe could be exposed to potential nest predation or competition from expanding grey squirrel populations within the current century, but population‐level effects currently appear to be unlikely. Current evidence shows that grey squirrels are unlikely to be significant predators of or competitors with nesting birds in their present or projected range in Europe. However, further studies of more species in different regions would be valuable, particularly in urban and suburban habitats.

InvasiBES: Understanding and managing the impacts of Invasive alien species on Biodiversity and Ecosystem Services

Invasive Alien Species (IAS) are amongst the most significant drivers of species extinction and ecosystem degradation, causing negative impacts on ecosystem services and human well-being. InvasiBES, a project funded by BiodivERsA-Belmont Forum for 2019–2021, will use data and models across scales, habitats and species to understand and anticipate the multi-faceted impacts of IAS and to provide tools for their management. Using Alien Species Narratives as reference, we will design future intervention scenarios focused on prevention, control and eradication of IAS in Europe and the United States, through a participatory process bringing together the expertise of scientists and stakeholders. We will also adapt current impact assessment protocols to assess both the detrimental and beneficial impacts of IAS on biodiversity and ecosystem services. This information will then be combined with maps of the potential distribution of Invasive Species of Interest in Europe under current and future climate-change scenarios. Likewise, we will anticipate areas under risk of invasion by range-shifting plants of concern in the US. Finally, focusing on three local-scale studies that cover a range of habitats (freshwater, terrestrial and marine), invasive species (plants and animals) and ecosystem services (supporting, provisioning, regulating and cultural), we will use empirical field data to quantify the real-world impacts of IAS on biodiversity and ecosystem services and calculate indicators of ecosystem recovery after the invader is removed. Spatial planning tools (InVEST) will be used to evaluate the costs and benefits of species-specific intervention scenarios at the regional scale. Data, models and maps, developed throughout the project, will serve to build scenarios and models of biodiversity and ecosystem services that are relevant to underpin management of IAS at multiple scales.

Prunus serotina in Italy: a challenging candidate for the national list of priority invasive alien species

In accordance with the European regulation on Invasive Alien Species (IAS), the black cherry tree (Prunus serotina Ehrh.) has recently been indicated as one of the 96 species proposed for the development of the national list of priority invasive alien species in Italy. The species, native to North America, is recognised as one of the most harmful IAS in Europe, given its high spread potential and the associated ecological and economic impacts reported in its alien range. Although P. serotina is recognised as a pest within the EU, plants are still available on the market, confirming intentional introduction as a current potential pathway for this species arrival into new areas. Since a comprehensive overview of the main features characterizing the invasive potential of this species is still lacking, we aim to underpin the high priority status of P. serotina as a IAS of main concern in Italy by outlining the main biological features, pathways and impacts of the black cherry in its secondary range. Management measures to be potentially included in specific action plans are also summarised.

Biocide Treatment of Invasive Signal Crayfish: Successes, Failures and Lessons Learned

Signal crayfish, as an invasive alien species in Europe, have caused impacts on aquatic communities and losses of native crayfish. Eradication of recently established populations may be possible in small ponds (<2.5 ha) and short lengths of small watercourses using a nonselective biocide. Between 2004 and 2012, a total of 13 sites in the U.K. were assessed for suitability. Six were treated with natural pyrethrum and crayfish were successfully eradicated from three. In Norway, five sites were assessed and two sites were treated with a synthetic pyrethroid, cypermethrin, both successfully. In Sweden, three sites were treated with another synthetic pyrethroid, deltamethrin, all successfully. Defining the likely extent of population was critical in determining the feasibility of treatment, as well as the ability to treat the whole population effectively. Important constraints on projects included site size, habitat complexity, environmental risks, cooperation of landowners and funding availability. Successful projects were manageably small, had good project leadership, had cooperation from stakeholders, had access to resources and were carried out within one to three years. Factors influencing success included treating beyond the likely maximum geographical extent of the population and taking care to dose the treated area thoroughly (open water, plus the banks, margins, inflows and outflows). Recommendations are given on assessing the feasibility of biocide treatments and project-planning.

Tehnološke lastnosti in uporabnost lesa velikega pajesena v primerjavi z lesom velikega jesena

Chinese sumac (Ailanthus altissima (Mill.) Swingle) is one of the most invasive alien species in Europe, and also in Slovenia. Due to its great renewal power the species is spreading rapidly, especially in abandoned agricultural and forest areas and along the traffic routes. It is botanically different from the European ash (Fraxinus excelsior L.), but it has similar tree habitus as well as similar structural characteristics of the wood. For this reason, we analysed the visual, anatomical and some physical and mechanical properties of both wood species. In all anatomical planes, the typical visual and colorimetric similarity of both studied woods was confirmed. Anatomically both ring porous wood species differ mainly in size and distribution of vessels, axial parenchyma and ray tissue. Wood of both species has a similar density as well, but the Chinese sumac has greater shrinkage. Some of the mechanical properties are comparable, although Chinese sumac wood has a lower modulus of elasticity and hardness and greater shear strength than ash wood. We can recommend that the wood of Chinese sumac can be used for production of pulp and paper, various panels and partly for less loaded constructions, which are not exposed to drastic climatic variability.

Temperature‐dependent development of Aproceros leucopoda (Hymenoptera: Argidae), an invasive pest of elms in Europe

AbstractThe temperature‐dependent development of Aproceros leucopoda Takeuchi, 1939 (Hymenoptera: Argidae), an invasive pest of elms in Europe, was studied in the laboratory on Siberian elm (Ulmus pumila) at six constant temperatures (10.9, 15.0, 19.5, 23.0, 24.3 and 27.0°C) and at a photoperiod of 16L:8D. The larvae of the species developed through 4–7 instars, and it was the 6th instar individuals of which continued their development at the highest rate. The developmental threshold (Tmin) and the thermal constant (K) were determined by the linear model and Lactin‐2 model for egg, larval, prepupal and pupal stages and one whole generation. The estimated values of Tmin and K by the two models for one generation were 7.3 and 7.1°C, and 426.5 and 432.7 degree‐days, respectively. Based on the survival and fecundity rates, the optimal temperature range for the species may be expected to be between 15.0 and 19.5°C. Allowing for the period of diapause, it was estimated that A. leucopoda might potentially develop through up to four or five generations per year in Hungary. These results may contribute to the better understanding of the biology of an invasive alien species in Europe.