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Aim Early warning against potentially harmful organisms of woody plant species can be achieved by sampling sentinel plants in exporting countries. However, it is unclear where sentinel plants can best be located, and how many samples are required and when and how often sampling optimally should take place for the adequate assessment of the biodiversity associated with the target plant species. We aimed to review spatial and temporal factors affecting associate biodiversity of single woody plant species and to develop guidance for the design of global biodiversity sampling studies. Location Worldwide. Taxon Insects and Fungi. Methods Literature about factors affecting the diversity of insects and fungi in association with single plant species on global, regional, local and different temporal scales was reviewed. Case studies of insect and fungal diversity, primarily collected on single plant species, and the cost of collecting and analysing samples from locations around the world were analysed. Results The review of the literature illustrated various factors affecting diversity, and the case studies allowed quantification of the relative impact of some spatial, temporal and financial aspects on captured biodiversity and, thus, illustrate the need to consider all possible factors that may affect the result of the sampling when deciding on a sampling design. Main conclusions Our study illustrates the factors that should be considered when deciding on the location and timing of sampling for sentinel plants, which is important because of the trade‐off between the number of samples and sampling locations needed to detect many of the species which may be potential pests, and the cost of (repeated) sampling in many locations. Decisions about the sampling design must be based on the objective of the sampling, but our recommendations apply irrespective of the targeted plant species or country.

Native to China, the Asian chestnut gall wasp, Dryocosmus kuriphilus (ACGW), was first found outside its native range in Japan and the Korean peninsula in the mid-twentieth century. After appearing in North America in 1974, it was found in Europe a few decades later. Since then, the gall wasp has spread throughout the distribution of chestnut in Europe. The ACGW’s discovery in North America and Europe elicited numerous studies to understand its invasive potential in these areas and how to control its spread and impact on chestnut production. Although endemic parasitoids responded positively to D. kuriphilus with low parasitism rates, the most effective management tactic has been classical biological control via the introduction of the parasitoid Torymus sinensis from its native range in China. This review summarizes the history of introduction, spread, and current distribution of D. kuriphilus , and highlights one of the most successful cases of classical biological control against a forest pest.

We show that the population ecology of the 9‐ to 10‐year cyclic, broadleaf‐defoliating winter moth (Operophtera brumata) and other early‐season geometrids cannot be fully understood on a local scale unless population behaviour is known on a European scale. Qualitative and quantitative data on O. brumata outbreaks were obtained from published sources and previously unpublished material provided by authors of this article. Data cover six decades from the 1950s to the first decade of twenty‐first century and most European countries, giving new information fundamental for the understanding of the population ecology of O. brumata. Analyses on epicentral, regional and continental scales show that in each decade, a wave of O. brumata outbreaks travelled across Europe. On average, the waves moved unidirectionally ESE–WNW, that is, toward the Scandes and the Atlantic. When one wave reached the Atlantic coast after 9–10 years, the next one started in East Europe to travel the same c. 3000 km distance. The average wave speed and wavelength was 330 km year⁻¹ and 3135 km, respectively, the high speed being incongruous with sedentary geometrid populations. A mapping of the wave of the 1990s revealed that this wave travelled in a straight E–W direction. It therefore passed the Scandes diagonally first in the north on its way westward. Within the frame of the Scandes, this caused the illusion that the wave moved N–S. In analogy, outbreaks described previously as moving S–N or occurring contemporaneously along the Scandes were probably the result of continental‐scale waves meeting the Scandes obliquely from the south or in parallel. In the steppe zone of eastern‐most and south‐east Europe, outbreaks of the winter moth did not participate in the waves. Here, broadleaved stands are small and widely separated. This makes the zone hostile to short‐distance dispersal between O. brumata subpopulations and prevents synchronization within meta‐populations. We hypothesize that hostile boundary models, involving reciprocal host–herbivore–enemy reactions at the transition between the steppe and the broadleaved forest zones, offer the best explanation to the origin of outbreak waves. These results have theoretical and practical implications and indicate that multidisciplinary, continentally coordinated studies are essential for an understanding of the spatio‐temporal behaviour of cyclic animal populations.

The species composition and abundance of phoretic mites of the bark beetles Pityokteines curvidens, P. spinidens, and P. vorontzowi on Silver fir (Abies alba) were investigated in 2003 at two locations (Trakoscan and Litoric) in Croatia. Stem sections and branches from A. alba trees infested by Pityokteines ssp. were collected and incubated in rearing cages. Bark beetles emerging from the stem sections and branches were examined for phoretic mites. A total of ten mite species were documented for the first time as associates of Pityokteines spp. on A. alba. These included Dendrolaelaps quadrisetus, Ereynetes scutulis, Histiostoma piceae, Paraleius leontonychus, Pleuronectocelaeno japonica, Proctolaelaps hystricoides, Schizostethus simulatrix, Tarsonemus minimax, Trichouropoda lamellose, and Uroobovella ipidis. T. minimax was the most frequent phoretic mite of all the three scolytines and U. ipidis was also common, whereas, the other mite species occurred less frequently. The species spectrum and relative abundance of mite associates were similar for all three Pityokteines species. Another species, Pleuronectocelaeno barbara was commonly found phoretic on P. curvidens, captured in pheromone traps in 2005 at the location Litoric. Furthermore, two previously collected mite specimens from Switzerland, phoretic on P. curvidens, were identified as Nanacarus sp. and Bonomia sp. The records from Croatia and Switzerland in the present study increase the number of known mite associates of Pityokteines spp. from one previously documented species to 14 species. None of the phoretic mites found in the survey in Croatia appear to have the potential to be used for biological control of Pityokteines spp., although the feeding habits are unknown for many species recorded.

The North American gall mite Aceria fraxiniflora was first recorded in Europe in southeast Hungary in 2017. Since then, it has shown a remarkably rapid spread on its host, the also North American green ash (Fraxinus pennsylvanica). By the beginning of 2023 it has been recorded in eight Central-Eastern European countries. In 2022 it was recorded on the other North American ash (Fraxinus Americana) in Zagreb (Croatia) and in Szarvas Arboretum (SE Hungary). Possible reasons and outcomes of this spread are discussed.

The aim of this research was to identify pathogens in field populations of the genus Pityokteines from Croatia with special reference to their spatial distribution throughout the country. Pathogens occurrence was studied in 5,968 adult specimens of three silver fir bark beetle species: Pityokteines curvidens, P. spinidens and P. vorontzovi. Four pathogen species were observed in different tissues of their hosts. The pathogens Canningia spinidentis and Menzbieria sp. were found only in P. spinidens, while Chytridiopsis typographi and Gregarina sp. were also present in P. curvidens and P. vorontzovi. Multiple infections were observed in all three beetle species where gregarines occurred together with C. typographi and in combination with C. spinidentis in the specimens of P. spinidens. All pathogen species found in this research are first descriptions on host Pityokteines spp., except Canningia spinidens. Data presented in this study show possible candidates for further tests to utilize pathogens as microbial control agents against fir bark beetles in the future.

Abstract Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

There is no sign of saturation in accumulation of alien species (AS) introductions worldwide, additionally the rate of spread for some species has also been shown to be increasing. However, the challenges of gathering information on AS are recognized. Recent developments in citizen science (CS) provide an opportunity to improve data flow and knowledge on AS while ensuring effective and high quality societal engagement with the issue of IAS (Invasive Alien Species). Advances in technology, particularly on-line recording and smartphone apps, along with the development of social media, have revolutionized CS and increased connectivity while new and innovative analysis techniques are emerging to ensure appropriate management, visualization, interpretation and use and sharing of the data. In early July 2018 we launched a European CO-operation in Science and Technology (COST) Action to address multidisciplinary research questions in relation to developing and implementing CS, advancing scientific understanding of AS dynamics while informing decision-making specifically implementation of technical requirements of relevant legislation such as the EU Regulation 1143/2014 on IAS. It will also support the EU biodiversity goals and embedding science within society. The Action will explore and document approaches to establishing a European-wide CS AS network. It will embrace relevant innovations for data gathering and reporting to support the implementation of monitoring and surveillance measures, while ensuring benefits for society and citizens, through an AS CS European network. The Action will, therefore, increase levels of participation and quality of engagement with current CS initiatives, ensuring and evaluating educational value, and improve the value outcomes for potential users including citizens, scientists, alien species managers, policy-makers, local authorities, industry and other stakeholders.

International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by high-throughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees.Measurement(s)metagenomics analysis • Cytochrome C Oxidase Subunit 1Technology Type(s)amplicon sequencing • Dideoxy Chain Termination DNA SequencingFactor Type(s)tree species • geographic location • mean annual temperature • mean annual precipitationSample Characteristic - OrganismFungi • InsectaSample Characteristic - Environmentdormant tree twigsMachine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.16764229