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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.

International audience; The international seed trade is considered relatively safe from a phytosanitary point of view and is therefore less regulated than trade in other plants for planting. However, the pests carried by traded seeds are not well known. We assessed insects and fungi in 58 traded seed lots of 11 gymnosperm and angiosperm tree species from North America, Europe, and Asia. Insects were detected by X-raying and molecular methods. The fungal community was characterized using high-throughput sequencing (HTS) and by growing fungi on non-selective agar. About 30% of the seed lots contained insect larvae. Gymnosperms contained mostly hymenopteran (Megastigmus spp.) and dipteran (Cecidomyiidae) larvae, while angiosperms contained lepidopteran (Cydia latiferreana) and coleopteran (Curculio spp.) larvae. HTS indicated the presence of fungi in all seed lots and fungi grew on non-selective agar from 96% of the seed lots. Fungal abundance and diversity were much higher than insect diversity and abundance, especially in angiosperm seeds. Almost 50% of all fungal exact sequence variants (ESVs) found in angiosperms were potential pathogens, in comparison with around 30% of potentially pathogenic ESVs found in gymnosperms. The results of this study indicate that seeds may pose a greater risk of pest introduction than previously believed or accounted for. A rapid risk assessment suggests that only a small number of species identified in this study is of phytosanitary concern. However, more research is needed to enable better risk assessment, especially to increase knowledge about the potential for transmission of fungi to seedlings and the host range and impact of identified species.

International audience; The number of invasive alien pest and pathogen species affecting ecosystem functioning, human health and economies has increased dramatically over the last decades. Discoveries of invasive pests and pathogens previously unknown to science or with unknown host associations yet damaging on novel hosts highlights the necessity of developing novel tools to predict their appearance in hitherto naive environments. The use of sentinel plant systems is a promising tool to improve the detection of pests and pathogens before introduction and to provide valuable information for the development of preventative measures to minimize economic or environmental impacts. Though sentinel plantings have been established and studied during the last decade, there still remains a great need for guidance on which tools and protocols to put into practice in order to make assessments accurate and reliable. The sampling and diagnostic protocols chosen should enable as much information as possible about potential damaging agents and species identification. Consistency and comparison of results are based on the adoption of common procedures for sampling design and sample processing. In this paper, we suggest harmonized procedures that should be used in sentinel planting surveys for effective sampling and identification of potential pests and pathogens. We also review the benefits and limitations of various diagnostic methods for early detection in sentinel systems, and the feasibility of the results obtained supporting National Plant Protection Organizations in pest and commodity risk analysis.

Arboreal fungal endophytes are a highly diverse group of organisms associated with asymptomatic tissues and some of them are latent pathogens. The knowledge of fungal endophytes is limited, because previous studies mainly focused on foliar fungal endophytes of a limited number of host species and locations. We assessed the fungal endophyte diversity in twigs of congeneric native and exotic tree species belonging to eleven angiosperm and gymnosperm genera in mostly temperate regions of 32 countries on six continents. We describe how host taxonomy and geographic location affect endophyte diversity and how diversity differs between native and exotic trees. More than 400 samples were collected on both hemispheres and fungal communities were assessed by high-throughput sequencing. Sampling was done in winter, because trees are mostly traded in winter, when deciduous trees lack foliage. We found around 15, 000 fungal Exact Sequence Variants (ESVs) associated with the tree genera. ESV richness varied among sampled taxa, but did not differ between native and exotic hosts. ESV richness in most of the northern hemisphere tree genera peaked at 45-50 degrees of latitude, but the pattern for southern hemisphere genera was not clear. The endophyte communities of angiosperms and gymnosperms differed ; around 30% of all ESVs were found in a single genus and less than 1% was found in all genera. Distinct geographic patterns among and within continents were found and the similarity of the endophyte communities decreased with distance between sampling locations in most genera. This study reveals fungal endophyte diversity on an unprecedented scale as a result of the wide geographic and taxonomic diversity of the samples. The geographic differences in ESVs in particular suggest that international live plant trade can facilitate the exchange of geographically isolated fungal communities, which could threaten tree-based resources in importing countries.

Live plants are often traded in their dormant stage, among other reasons to reduce the introduction of new pests. However, the pests associated with this pathway are largely unknown. Risk mitigation relies on pest risk assessments which can only be performed for known pests. It is therefore important to identify potential pests before the introduction occurs. In addition, post arrival host shifts are very difficult to predict. Several studies attempted to estimate the likelihood of host shifts based on existing literature data on known pest-host associations, but the number of pests in these studies was often limited and the data were unlikely collected in the same place and at the same time. To overcome these problems, we performed a global study which aimed at detecting potential insect pests and fungal pathogens on selected congeneric native and exotic tree species in 33 countries. Samples were taken in botanical gardens and arboreta on the Northern and Southern hemisphere. At each location, twenty 50 cm long twigs were collected from tree species of up to six genera and kept in containers with water at room temperature for insect emergence. Emerged insects were collected and identified based on morphology and DNA barcoding of the mitochondrial DNA COI region. DNA was also extracted from pooled buds, twig parts and needles for the identification of fungi based on the ribosomal DNA ITS region using a high-throughput sequencing approach. Here, we present the first results of this study and discuss them in the context of pest risk assessment.

Background and purpose: Dryocosmus kuriphilus is considered as one of the major pests of sweet chestnut and the effective method of controlling its populations and damage is the biological control with its introduced parasitoid Torymus sinensis. T. sinensis is a univoltine, host specific parasitoid, phenologically synchronized and morphologically adapted to D. kuriphilus . It has a good dispersal ability, it builds up populations quickly and it effectively controls the pest already few years after the release. In this paper we describe the first results of the introduction and release of T. sinensis for controlling the populations of invasive D. kuriphilus in sweet chestnut forests and orchards in Croatia, Hungary and Slovenia. Materials and methods: Withered D. kuriphilus galls with T. sinensis larvae were collected in Torino vicinities, Italy, in March 2014 and March 2015. After emergence, males and females were put together, kept at 14°C and fed with liquid honey until the release. To confirm the establishment of the population of T. sinensis on release site from 2014 in Croatia morphological and DNA identification were used. Fresh galls from the release site of Pazin, Croatia were collected in spring 2015 and parasitism rates of T. sinensis were calculated. Results and conclusions: In total 10,590 females and 5,295 males of T. sinensis were released in sweet chestnut forests in Croatia, Hungary and Slovenia in 2014 and 2015. The minimum release number of T. sinensis was 100 females/50 males and the maximum was 1,200 females per site. Subsequent releases with a larger number of females (1,200 and 800 in two years) resulted in a rapid establishment of the population of T. sinensis and parasitism rates of 76% only one year after the first release was done . The establishment of the population of T. sinensis was confirmed with molecular analyses and morphological identification. Obtained haplotype sequences of T. sinensis have shown similarities with Torymus beneficus. Prior to the release of T. sinensis , all advantages and disadvantages of the introduction of this alien biocontrol species into natural stands in Croatia, Hungary and Slovenia have been considered.