The European spruce bark beetle (Ips typographus) has driven unprecedented forest losses in Europe. Detecting infested trees before brood emergence is crucial for control. We present the first multi-country benchmark of pre-emergence detection using drone remote sensing. Data span Sweden, Finland, Italy, and Czechia (12 areas; 6 time series), with 26 multispectral and 16 hyperspectral image sets, covering 1798 infested and 13,020 healthy trees. We compare detection performance across remote sensing factors and tree-decline dynamics. Hyperspectral sensors performed best due to access to green-shoulder bands (similar to 530 nm): the Green Shoulder Curvature Ratio (GSCRms) index detected up to twice as many infestations as the next-best spectral index (VI). Without these bands, hyperspectral and multispectral sensors were comparable using narrow- or broadband VIs. Within the red-edge, the 705-712 nm bands were 2-4 times more sensitive to stress than the 730-740 nm bands, guiding the choice of multispectral sensors. Normalizing red-edge VIs to pre-attack values markedly improved early detection and reduced false positives; green-shoulder VI was inherently stable and required no normalization. Outbreak timing was broadly similar among countries, but the decline progressed faster for trees attacked at outbreak peak. Decline was highly localized: adjacent plots often differed largely in decline rate (e.g., 50% vs. 17%). Localized decline rate dominated detectability, followed by outbreak phase, green-shoulder-band availability, red-edge wavelength, and VI normalization.

1. European coniferous forests are increasingly vulnerable to forest disturbances due to climate change and more frequent extreme events, which can trigger forest pest outbreaks. In the Italian South-Eastern Alps, the 2018 Vaia storm led to massive outbreaks of the European spruce bark beetle (Ips typographus L.) (Coleoptera: Curculionidae, Scolytinae), severely affecting Norway spruce forests. Sanitation felling (i.e., removal of infested trees) is a common management practice, but its efficacy in reducing bark beetle populations is variable and context-dependent. 2. This study assesses the effect of sanitation felling performed in 2022 in Friuli Venezia Giulia (NE Italy) on bark beetle damage that occurred in 2023 across eight spruce forest types, as evaluated using multispectral satellite imagery. Information about forest composition was retrieved from local databases to assess how forest characteristics influence sanitation felling effectiveness. 3. Results show that bark beetle damage was effectively reduced only at very high or very low sanitation felling rates. Sanitation felling increasing up to similar to 50% produced an increasing damage, while damage decreased progressively only over 50% sanitation felling. Pure spruce forests, especially mountain spruce forest and spruce plantations, were the most affected forest categories, while damage was reduced in alpine (i.e., >1500 m elevation) and mixed formations. Sanitation felling above 50% proved effective in significantly reducing damage within the pure spruce neo-reforestations and the pure subalpine spruce forests. 4. Findings call for an integrated approach to compensate for the limitations of sanitation felling, to plan targeted interventions and help promote more resilient forest ecosystems to mitigate future outbreaks.

Addressing the challenges posed by Non-Indigenous Species (NIS) demands coordinated efforts across terrestrial, freshwater and marine ecosystems. In this study, we engaged a diverse group of 90 Italian researchers operating within these three domains to identify and assess strategies for advancing NIS research, using a structured, interactive and expert-driven methodology. The process began with a comprehensive evaluation of ongoing activities, research methodologies and specific needs. This assessment provided information for the development of an initial set of suggestions to ameliorate NIS research, which were collectively discussed and refined, leading to the identification of six good practices identified by the acronym TRACKS and described as: i) Tracking NIS in biodiversity data collection; ii) Reference protocols for NIS data collection; iii) Active participation; iv) Collaboration and FAIR principles; v) Knowledge hub for NIS data; vi) Strategic communication. A SWOT framework was then applied to analyse the internal and external factors influencing the Strengths, Weaknesses, Opportunities and Threats associated with each good practice. Consensus-building techniques were used throughout the evaluation process to ensure the robustness of outcomes. Finally, a quantitative assessment of the SWOT analysis revealed a strong consensus amongst experts regarding the various strengths, weaknesses, opportunities and threats of the different good practices, along with a general optimism about the opportunities and strengths associated with their implementation. Developed within the Italian research community, this approach offered valuable insights to researchers worldwide working on NIS and enabled the expert assessment of six best practices that may serve as a benchmark for advancing the science of biological invasions.

Abstract The European Commission submitted to the EFSA Panel on Plant Health a Dossier from the United States proposing the use of a vacuum–steam–heat treatment as a stand‐alone phytosanitary measure to mitigate the risk of entry of Bretziella fagacearum, Geosmithia morbida and its vector Pityophthorus juglandis (thousand cankers disease complex) into the EU when trading oak (Quercus alba, Q. rubra) and walnut (Juglans nigra) logs with bark from the US. The proposed treatment consists of heating the sapwood to 56°C for 30 min at a depth of 5 cm from the cambium under vacuum and steam conditions. EFSA assessed the likelihood that logs of oak and walnut target species would be free from EU quarantine pests, basing its evaluation solely on the efficacy of the proposed treatment. In addition to B. fagacearum, G. morbida and P. juglandis, 14 other EU quarantine pests were identified as relevant because they are present in the US and are potentially associated with the commodities. The assessment was based on the information provided by the applicant country and on systematic literature reviews conducted by EFSA to determine the survival temperature and wood colonisation depth of the target pests. The evidence gathered was evaluated through an Expert Knowledge Elicitation (EKE) to estimate the likelihood of pest freedom of logs after the treatment assuming that all logs were infested. The vacuum–steam–heat treatment substantially reduces the presence of target pests infesting the sapwood. The EKE indicated with 95% certainty that between 9021 and 10,000 treated Q. alba logs per 10,000 and that between 9347 and 10,000 treated Q. rubra logs per 10,000 will be free from B. fagacearum. The EKE indicated with 95% certainty that between 9862 and 10,000 treated J. nigra logs per 10,000 will be free from G. morbida and that between 9948 and 10,000 treated J. nigra logs per 10,000 will be free from P. juglandis. However, the treatment is expected to be much less effective against pests which infest wood deeper than 5 cm from the cambium such as the species Arrhenodes minutus. The EKE indicated with 95% certainty that between 1109 and 10,000 logs per 10,000 will be free from A. minutus.

Outbreaks of the European spruce bark beetle (Ips typographus) increasingly threaten Picea abies forests under climate stress. Semiochemical "push-and-pull" systems, combining anti-attractants with pheromone-baited traps, are widely promoted, yet their performance under outbreak pressure and operational constraints remains understudied. In 2023, we evaluated push, push-and-pull, and control treatments in a multi-site field experiment across five Alpine localities during high-pressure outbreak. Push treatments used anti-attractant blend based on non-host volatiles and inhibitory host compounds (1-hexanol, 1-octen-3-ol, 3-octanol, 1,8-cineole, trans-conophthorin, trans-4-thujanol). Push-and-pull plots additionally included three MultiWit slot traps, baited with the aggregation pheromone Pheroprax (c) and placed along the forest edge similar to 25 m from treated trees at low trap density. Contrary to prevailing expectations, pheromone trap addition increased tree infestation relative to both push and control treatments. Push and control did not differ significantly, although no infested trees occurred under push. Monitoring traps used to assess background beetle pressure showed similar catches among treatments. Spatial mapping revealed that beetle-killed trees were concentrated near push-and-pull plots, consistent with beetle attraction to trap lures combined with insufficient interception capacity of traps. Our results provide field evidence that semiochemical protection outcomes depend on deployment configuration, not chemical composition alone. Under operational conditions with limited trapping infrastructure, push treatments did not increase attack rates, whereas push-and-pull was associated with higher infestation. These findings demonstrate strong context dependence in semiochemical strategies, highlighting the importance of trap density and spatial arrangement when designing bark beetle protection programmes.

Abstract The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as ‘High risk plants, plant products and other objects’. This Scientific Opinion covers plant health risks posed by unrooted cuttings of Salix species (S. aegyptiaca, S. eriocephala, S. gmelinii, S. miyabeana, S. purpurea, S. rehderiana, S. schwerinii, S. udensis, S. viminalis) imported from the United Kingdom (UK). The assessment was performed considering the available scientific information, including the technical information provided by the UK. All pests potentially associated with the commodities were evaluated against specific criteria. Only two EU Regulated pests (the fungus Entoleuca mammata and the oomycete Phytophthora ramorum (non‐EU isolates)), present in the UK and potentially associated with the commodity, were considered as relevant for this Opinion. No pests non‐regulated in the EU were identified to be selected for further evaluation.

In the last few decades, bark beetle outbreaks have increased in European forests, triggered by extreme weather events, such as drought and windstorms. A core element of integrated pest management to control outbreaks are salvage logging and sanitation felling, i.e., the timely removal or treatment of potential brood material and already infested trees after disturbance events. Associated with these management operations as well as with regular, planned thinning and cutting, felling residues, such as treetops, branches and stumps that remain in the forest provide potentially suitable breeding material for bark beetles and may trigger further outbreak events. Although felling residue management is part of regular forest management in most of Europe, no overview exists on its use throughout the continent. To fill this gap, we gathered forest health experts from 20 European countries and used a questionnaire to provide information on felling residue management in the context of forest protection in managed forests. Relevant legislation in these countries was reviewed for regulations concerning this topic. We found that most countries have felling residue management in their legislation and/or perform it in practice. In 12 of the 20 countries, felling residue management is being applied to manage bark beetles, particularly in areas that have experienced large-scale outbreaks in the last few decades. Felling residues are mainly managed in forests dominated by Norway spruce (Picea abies L. Karst) and pines (Pinus spp.) (in 19 and 17 of the countries, respectively). The most frequently used management methods on a European level were piling or mulching of felling residues. These methods were used in 14 and 16 of the countries, respectively. Besides bark beetle management, use of residues for bioenergy (4 countries) and biodiversity conservation (6 countries) was reported. The diversity of felling residue management practices across Europe may reflect differences in forest policies and climatic gradients that are affecting bark beetle outbreak risks. This overview presents the variety of felling residue management applied across 20 European countries, highlighting the reasons for and implications of its use, as well as further research needs.

Tomicus destruens (Wollaston), the Mediterranean pine shoot beetle, has long been confused with Tomicus piniperda (Linnaeus) in Greece, as well as in many other Mediterranean countries. To clarify its presence and population structure, we analyzed COI sequences of specimens from 21 Greek sites (including islands) and compared them with samples from central (Italy) and western (Spain) Mediterranean populations. Greek populations were dominated by a single haplotype (Td06), whereas Samothraki Island harbored several private haplotypes, indicating long localized lineage persistence. In contrast, Italian and Spanish populations showed high haplotype diversity with many region-specific lineages, consistent with long-term refugial stability in the central-western Mediterranean. Physiological measurements further differentiate the two species: the mean supercooling point (SCP) of Greek T. destruens (–12.3 °C) was substantially higher than reported for T. piniperda (≈–18 °C), demonstrating lower cold tolerance. This supports its restriction to mild Mediterranean climates. Overall, our results confirm the dominant occurrence of T. destruens with no recovery of T. piniperda individuals in Greece and highlight the combined value of genetic and physiological markers for resolving species boundaries and understanding Mediterranean bark beetle biogeography.

International trade poses a growing threat to global biosecurity, with bark- and wood-boring beetles representing a major concern for forest health. Non-native species are frequently introduced at points of entry, where populations can establish in the surrounding landscape. To improve early detection, generic surveillance programs use traps in these high-risk areas, collecting a broad spectrum of species. These traps also capture native beetles, providing insights into the potential species pool that could become exotic elsewhere. However, implementing effective landscape-wide surveillance within reasonable resource limits remains challenging. In this study, we used trapping data of Cerambycidae and Scolytinae from 11 high-risk areas across Europe and North America to develop practical recommendations for generic surveillance at multiple spatial scales. Specifically, we attempted to address two key questions: (1) how to maximize the single-trap efficacy depending on the trap surroundings; and (2) how many traps should be used in a landscape-wide sampling depending on landscape composition. Under budget constraints, we recommend prioritizing trap placement within forest patches and avoiding locations surrounded by roads or buildings. Urban-dominated landscapes required greater sampling effort (i.e., more traps) than forest-dominated landscapes. Deploying fewer than four traps per square kilometer might lead to an incomplete representation of the local bark- and wood-boring beetle community, losing about 30%-50% of species. Overall, our findings highlight the importance of incorporating landscape ecology into generic surveillance planning to optimize trap effectiveness within resource limitations.

Bark beetle outbreaks are intensifying under climate change, yet the links among drought stress, beetle attack and colonization, rapid tree mortality, and tree physiology, remain poorly integrated across disciplines. This review provides a comprehensive, mechanistic synthesis of recent advances in tree physiology, bark beetle ecology, and microbial interactions to examine how drought alters xylem–phloem function, carbon allocation, and defense capacity, how these changes affect beetle host selection and reproductive success, and how associated microbes accelerate host decline. Drought-driven declines in xylem water potential constrain phloem transport through reduced turgor and increased sap viscosity, reshaping carbon distribution and defense deployment. Moderate drought may transiently enhance some defenses, whereas severe or prolonged drought depletes non-structural carbohydrates, impairs resin flow, and increases phloem nutritional suitability for beetles. Beetle attacks cause spatially complex phloem disruption and local carbon depletion together with their associated fungi, which also contribute to pit membrane degradation, increasing vulnerability to embolism. The altered bark and phloem microenvironments, including gas exchange and moisture conditions within bark beetle galleries, may further influence microbial activity and host responses. We propose a cross-disciplinary, integrated mechanistic framework in which drought-induced physiological destabilization predisposes trees to beetle attack, after which phloem disruption and microbial activity amplify carbon limitation and hydraulic dysfunction. Hydraulic failure may represent a convergence point among interacting stressors, underscoring the complex multi-trophic feedbacks driving infestation expansion. Key gaps remain in quantifying phloem dynamics, bark permeability, and subcortical microclimates during attack, limiting predictions of forest vulnerability under increasing drought and bark beetle pressure.

Recent increases in forest damage across Europe have challenged national forestry sectors and threatened progress toward Europe's climate and bioeconomy goals. Although developments in remote sensing now allow large-scale wall-to-wall monitoring of forest conditions, reliable damage assessments still require robust terrestrial data. Yet, existing data often remain inconsistent and fragmentarily distributed across institutions and countries. Based on consultations with national experts, we here provide an evaluation of national forest damage survey programmes in 19 European countries, identify obstacles that hinder more effective use of data, and formulate recommendations to overcome these barriers. We examined five aspects of national forest damage surveys: (i) legal and institutional frameworks, (ii) data acquisition methods, (iii) damage attribution, (iv) data quality and consistency, and (v) data accessibility. We found that half of the examined programs have changed protocols since 2000 and only 53 % of countries currently have survey programs covering their entire forest area. In 26 % of countries, legal constraints hamper data accessibility to the broader international community, while in 89 % data are available only in the respective national languages. In 84 % of countries, the absence of adequate metadata hinders the usability of the data without inside knowledge. Some of Central European countries operate the most consistent and open systems, while western and northern countries generally exhibited lower levels of openness and consistency. The implementation of coordinated structural changes in national programs that would enable consistent monitoring of forest damage at European level is unrealistic in the foreseeable future. However, certain critical gaps in data coverage, completeness, and consistency can be addressed through extensive data post-processing and integration with remote sensing. Overcoming barriers, such as limited awareness of the importance of transnational assessments, requires improved communication efforts and targeted funding programs. Establishing a coordination unit by leveraging existing policy processes in Europe appears essential to advancing these efforts.

Ambrosia beetles of the subfamily Scolytinae (Coleoptera: Curculionidae) have successfully invaded many parts of the world and are increasingly being introduced to new areas, primarily through international trade. The number of non-native species recorded in Slovenia is also increasing. During the national survey of quarantine species in 2024, a new non-native scolytine beetle, Cnestus mutilatus, was recorded for the first time in Slovenia. Two specimens were trapped at Radmožanci, a location in northeastern Slovenia. New data on two other species recently recorded in Slovenia, Anisandrus maiche and Xylosandrus compactus, are also presented.

Abstract The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as ’High‐risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by Acer plants (A. griseum, A. platanoides, A. rubrum, A. saccharum, A. saccharinum, A. tataricum and A. tataricum subsp. ginnala, Acer × freemani) imported from Ukraine as dormant plants: (a) 1–4 years old bare root plants and (b) 1–2 years old plants in pots, taking into account the available scientific information, including the technical information provided by Ukraine. All pests associated with the commodity were evaluated against specific criteria for their relevance for this opinion. Two EU protected zone quarantine pests, i.e. Cryphonectria parasitica, and Entoleuca mammata and one EU‐quarantine pest, i.e. Lopholeucaspis japonica fulfilled all relevant criteria and were selected for further evaluation. For the selected pests, the risk mitigation measures proposed in the technical dossier from Ukraine were evaluated taking into account the possible limiting factors. For the selected pests an expert judgement is given on the likelihood of pest freedom taking into consideration the distribution of the pest in Ukraine, risk mitigation measures acting on the pest and uncertainties associated with the assessment. The degree of pest freedom varies among the pests evaluated, with L. japonica being the pest most frequently expected on imported plants. The Expert Knowledge Elicitation (EKE) indicated with 95% certainty that between 9748 and 10,000 per 10,000 bare root 1–4 years old plants will be free from L. japonica.

The European Commission requested the EFSA Panel on Plant Health to deliver a risk assessment on the likelihood of pest freedom from regulated EU quarantine pests, with emphasis on Bursaphelenchus xylophilus and its vectors Monochamus spp. of debarked conifer wood chips fumigated with sulfuryl fluoride as proposed by the United States (US) and as outlined in ISPM 28 - PT23 of sulfuryl fluoride (SF) fumigation treatment for nematodes and insects in debarked wood. The assessment considered the different phases in the wood chips' production, with special emphasis on the SF treatment. In addition to B. xylophilus and its vectors Monochamus spp., 22 EU quarantine pests and protected zone quarantine pests, some of which are regulated as groups of pests by the Commission Implementing Regulation (EU) 2019/2072, are present in the US and are potentially associated with the commodity. For these pests an expert judgement is given on the likelihood of pest freedom taking into consideration the available scientific information and technical information provided by the US, including uncertainties associated with the assessment. The likelihood of pest freedom varies among the pests evaluated, with B. xylophilus being the pest most frequently expected on the commodity. The Expert Knowledge Elicitation (EKE) indicated with 95% certainty that between 9491 and 10,000 m3 of debarked conifer wood chips treated with SF per 10,000 m3 will be free from B. xylophilus, and that between 9987 and 10,000 m3 of wood chips per 10,000 m3 will be free from Monochamus spp. Technical elements which are critical for a successful treatment and for minimising the presence of Union quarantine pests on the commodity are identified and described in the opinion. In particular, it is important to note that SF treatments are generally less effective in eliminating fungi than insects, the required parameters of the fumigation should be met at all points of the pile of wood chips and the time of storage of wood chips before treatment should be kept as short as possible because B. xylophilus can easily reproduce and spread throughout the pile under conducive conditions.

Little is known about the influence of mating strategies that could potentially facilitate the colonization of new hosts in outbreeding species of the weevil subfamily Scolytinae. Individuals typically emerge from their host tree, disperse, and then mate with unrelated conspecifics in a new host where the females establish maternal galleries. Yet, in several spe-cies commonly classified as outbreeding, females have been found already mated before host colonization. Precolonization mating provides female with a sperm supply before they find a new host and allows them to establish a maternal gallery on their own. We compared the proportion of females mated before host colonization across 18 European and four American outbreeding Scolytinae species using a phylogenetically controlled analysis. To this end, we determined whether females caught in the spring had sperm in their spermathecae. We found that a proportion of females (range: 16-100%) mated before host colonization in all 22 species. Moreover, this trait was biased, although not significantly, toward invasiveness. Species known to have established outside their native range (Scolytinae with an Invasion History-SIH) displayed a higher proportion of females mated before host colonization than did species restricted to their native range (non-SIH). In Hylurgus ligniperda (Fabricius), a Palearctic species currently present across the globe, the proportions of females mated before host colonization reach 90% in the species' native range and up to 99% in its nonnative range (Argentina and New Zealand). Overall, these results show that precolonization mating is widespread among the Scolytinae. This trait could enhance the invasive capacities of outbreeding species by allowing females to establish a maternal gallery independently of any male during colonization, thus facilitating the establishment and spread of species introduced in new geographical areas.

IntroductionEuropean forests face increasing threats from climate change-induced stressors, which create favorable conditions for bark beetle outbreaks. The most critical spruce forest pest in Europe is the European Spruce Bark Beetle (Ips typographus L.). Effective forest management of this beetles’ outbreaks necessitates timely detection of recently attacked spruce trees, which is challenging given the difficulty in identifying symptoms on infested tree crowns, especially over large areas. This study assessed the detectability of infested trees over large spruce dominated areas (20–60 ha) using high-resolution drone multispectral imagery.MethodsA multispectral sensor mounted on an Unmanned Aerial Vehicle (UAV) was used to capture images of the investigated spruce stands weekly during June 2023. These were used to compute the reflectance of all single trees, derive vegetation indices, and then compare these between bark beetle infested trees and healthy ones.ResultsThe results showed that it was possible to separate the spectral features of recently infested trees from the healthy trees during the final developmental stage of the first beetles’ generation, despite the limitations due to difficulties in image processing over large areas. The best performing vegetation indices included NDRE (Normalized Difference Red Edge index) and GNDVI (Green Normalized Difference Vegetation Index), which allowed the earlier separation between infested and healthy trees.DiscussionThe study shows that the use of UAV high-resolution imagery can present some limitations when performing early detection over larger areas. The integration of sensors focused on narrower spectral windows around the Red-Edge and Green bands and other remote sensing methods (e.g., satellite imagery) could help overcome these limitations and improve early-detection over large forest areas. The proposed early-detection approach will increase the understanding of which factors to consider when performing early detection with remote sensing techniques. In particular, it will add insights when upscaling to larger spatial scales, providing useful guidance for the management of areas suffering pest outbreaks.

Ongoing shifts in climate and land use have altered interactions between trees and insect herbivores, changing biotic disturbance regimes. However, as these changes are complex and vary across host species, insect taxa, and feeding guilds, they remain poorly understood. We compiled annual records of forest insect disturbance from 15 countries in temperate and boreal Europe, spanning the period from 2000 to 2022. The dataset comprises 1361 time series characterizing the dynamics of 50 herbivorous insects. We used this dataset to test whether insect disturbance has systematically changed during the 23-year period across host trees and feeding guilds, whether it varies along latitudinal and climatic gradients, and whether synchrony exists among species in the same guild or among species sharing the same host. Since 2000, borer disturbance was predominantly concentrated on gymnosperms, while defoliators impacted gymnosperms and angiosperms more evenly. While 85.8% of gymnosperm disturbance was inflicted by a single species, Ips typographus, the majority of disturbances to angiosperms were caused by six different species. Borer impact on gymnosperms has increased in the 21st century, while defoliator impact has decreased across both clades. In contrast to diverging temporal trends, disturbance was consistently greater in warmer and drier conditions across feeding guilds and host types. We identified significant synchrony in insect disturbance within host types and feeding guilds but not between these groups, suggesting shared drivers within guilds and host types. Increasing insect disturbance to gymnosperms may catalyze adaptive transformations in Europe's forests, promoting a shift from historical conifer-dominated management to broadleaved trees, which are less affected by insect herbivores. Our findings reveal a diversity of trends in insect herbivory, underscoring the need to strengthen monitoring and research in order to better understand underlying mechanisms and identify emerging threats that may not be apparent in currently available data.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by plants of Populus alba, Populus nigra and Populus tremula imported from the United Kingdom (UK) as: (a) 1- to 7-year-old bare root plants, (b) 3- to 15-year-old plants in pots, (c) 1- to 2-year-old cell grown plants and (d) bundles of 1- to 2-year-old cuttings/graftwood (only for P. nigra and P. tremula), taking into account the available scientific information, including the technical information provided by the UK. All pests associated with the commodity were evaluated against specific criteria for their relevance for this Opinion. Two EU protected zone quarantine pests, i.e. Bemisia tabaci (European populations) and Entoleuca mammata, fulfilled all relevant criteria and were selected for further evaluation. For the selected pests, the risk mitigation measures implemented in the technical dossier from the UK were evaluated taking into account the possible limiting factors. Expert judgements were given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The age of the plants was considered, reasoning that older trees are more likely to be infested mainly due to longer exposure time and larger size. The degree of pest freedom varies between the pests evaluated, with E. mammata being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation (EKE) indicated with 95% certainty that between 9730 and 10,000 per 10,000 P. tremula rooted plants in pots (3 to 15 year old) will be free from E. mammata.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by plants of Taxus baccata imported from the United Kingdom (UK) as: (a) bundles of 2-year-old bare root plants (whips), (b) 2- to 7-year-old bare root plants, either exported as single plants or in bundles, (c) 2-year-old cell grown plants exported in bundles, and (d) 3- to 15-year-old plants in pots. The assessment was performed considering the available scientific information, including the technical information provided by the UK. All pests associated with the commodity were evaluated against specific criteria for their relevance for this opinion. One EU quarantine pest, Phytophthora ramorum (non-EU isolates) fulfilled all relevant criteria and was selected for further evaluation. For the selected pest, the risk mitigation measures implemented in the technical dossier from the UK were evaluated taking into account the possible limiting factors. An expert judgement was given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The fact that T. baccata is an evergreen plant on which P. ramorum can cause foliar infection was considered a critical element in the risk assessment. In addition, the age of the plants was considered, reasoning that older trees are more likely to be infected mainly due to longer exposure time and larger size. The degree of pest freedom slightly differs between bare root plants (including whips) and plants in pots (including cell grown plants), with plants in pots being less likely pest free. The Expert Knowledge Elicitation (EKE) indicated with 95% certainty that between 9699 and 10,000 3- to 15-year-old plants in pots and bundles of 2-year-old cell grown plants per 10,000 will be free from P. ramorum (non-EU isolates).