A Synoptic Review of Plant Disease Epidemics and Outbreaks Published in 2022.

This scientometric study reviews the scientific literature and CABI distribution records published in 2022 to find evidence of major disease outbreaks and first reports of pathogens in new locations or on new hosts. This is the second time we have done this, and this study builds on our work documenting and analyzing reports from 2021. Pathogens with three or more articles identified in 2022 literature were Xylella fastidiosa, Bursaphelenchus xylophilus, Meloidogyne species complexes, 'Candidatus Liberibacter asiaticus', Raffaelea lauricola, Fusarium oxysporum formae specialis, and Puccinia graminis f. sp. tritici. Our review of CABI distribution records found 29 pathogens with confirmed first reports in 2022. Pathogens with four or more first reports were Meloidogyne species complexes, Pantoea ananatis, grapevine red globe virus, and Thekopsora minima. Analysis of the proportion of new distribution records from 2022 indicated that grapevine red globe virus, sweet potato chlorotic stunt virus, and 'Ca. Phytoplasma vitis' may have been actively spreading. As we saw last year, there was little overlap between the pathogens identified by reviewing scientific literature versus distribution records. We hypothesize that this lack of concordance is because of the unavoidable lag between first reports of the type reported in the CABI database of a pathogen in a new location and any subsequent major disease outbreaks being reported in the scientific literature, particularly because the latter depends on the journal policy on types of papers to be considered, whether the affected crop is major or minor, and whether the pathogen is of current scientific interest. Strikingly, too, there was also no overlap between species assessed to be actively spreading in this year's study and those identified last year. We hypothesize that this is because of inconsistencies in sampling coverage and effort over time and delays between the first arrival of a pathogen in a new location and its first report, particularly for certain classes of pathogens causing only minor or non-economically damaging symptoms, which may have been endemic for some time before being reported. In general, introduction of new pathogens and outbreaks of extant pathogens threaten food security and ecosystem services. Continued monitoring of these threats is essential to support phytosanitary measures intended to prevent pathogen introductions and management of threats within a country.

What Can Be Learned by a Synoptic Review of Plant Disease Epidemics and Outbreaks Published in 2021?

A synoptic review of plant disease epidemics and outbreaks was made using two complementary approaches. The first approach involved reviewing scientific literature published in 2021, in which quantitative data related to new plant disease epidemics or outbreaks were obtained via surveys or similar methodologies. The second approach involved retrieving new records added in 2021 to the CABI Distribution Database, which contains over a million global geographic records of organisms from over 50,000 species. The literature review retrieved 186 articles, describing studies in 62 categories (pathogen species/species complexes) across more than 40 host species on six continents. Pathogen species with more than five articles were Bursaphelenchus xylophilus, 'Candidatus Liberibacter asiaticus', cassava mosaic viruses, citrus tristeza virus, Erwinia amylovora, Fusarium spp. complexes, F. oxysporum f. sp. cubense, Magnaporthe oryzae, maize lethal necrosis co-infecting viruses, Meloidogyne spp. complexes, Pseudomonas syringae pvs., Puccinia striiformis f. sp. tritici, Xylella fastidiosa, and Zymoseptoria tritici. Automated searches of the CABI Distribution Database identified 617 distribution records new in 2021 of 283 plant pathogens. A further manual review of these records confirmed 15 pathogens reported in new locations: apple hammerhead viroid, apple rubbery wood viruses, Aphelenchoides besseyi, Biscogniauxia mediterranea, 'Ca. Liberibacter asiaticus', citrus tristeza virus, Colletotrichum siamense, cucurbit chlorotic yellows virus, Erwinia rhapontici, Erysiphe corylacearum, F. oxysporum f. sp. cubense Tropical race 4, Globodera rostochiensis, Nothophoma quercina, potato spindle tuber viroid, and tomato brown rugose fruit virus. Of these, four pathogens had at least 25% of all records reported in 2021. We assessed two of these pathogens-tomato brown rugose fruit virus and cucurbit chlorotic yellows virus-to be actively emerging in/spreading to new locations. Although three important pathogens-'Ca. Liberibacter asiaticus', citrus tristeza virus, and F. oxysporum f. sp. cubense-were represented in the results of both our literature review and our interrogation of the CABI Distribution Database, in general, our dual approaches revealed distinct sets of plant disease outbreaks and new records, with little overlap. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Epidemiology and Management of Plant Viruses Under a Changing Climate.

Plant viruses are an ever-present threat to agricultural production and provide a wide array of symptoms resulting in economic losses throughout the world. Diseases can be transmitted by insect vectors, as well as through pollen, seed, and other means. With the increased globalization of agriculture, the introduction of new viruses from exotic locations and their establishment in new production regions and even new crops is a growing concern. Advancing knowledge of the epidemiology of plant viruses including development of new diagnostic methods, virus surveillance, and modeling, virus ecology and evolution, virus interactions with insect vectors, and other factors are important toward reducing the spread of plant viruses and managing virus diseases.

Coinfections by noninteracting pathogens are not independent and require new tests of interaction.

If pathogen species, strains, or clones do not interact, intuition suggests the proportion of coinfected hosts should be the product of the individual prevalences. Independence consequently underpins the wide range of methods for detecting pathogen interactions from cross-sectional survey data. However, the very simplest of epidemiological models challenge the underlying assumption of statistical independence. Even if pathogens do not interact, death of coinfected hosts causes net prevalences of individual pathogens to decrease simultaneously. The induced positive correlation between prevalences means the proportion of coinfected hosts is expected to be higher than multiplication would suggest. By modelling the dynamics of multiple noninteracting pathogens causing chronic infections, we develop a pair of novel tests of interaction that properly account for nonindependence between pathogens causing lifelong infection. Our tests allow us to reinterpret data from previous studies including pathogens of humans, plants, and animals. Our work demonstrates how methods to identify interactions between pathogens can be updated using simple epidemic models.

Epidemiological and ecological consequences of virus manipulation of host and vector in plant virus transmission.

Many plant viruses are transmitted by insect vectors. Transmission can be described as persistent or non-persistent depending on rates of acquisition, retention, and inoculation of virus. Much experimental evidence has accumulated indicating vectors can prefer to settle and/or feed on infected versus noninfected host plants. For persistent transmission, vector preference can also be conditional, depending on the vector's own infection status. Since viruses can alter host plant quality as a resource for feeding, infection potentially also affects vector population dynamics. Here we use mathematical modelling to develop a theoretical framework addressing the effects of vector preferences for landing, settling and feeding-as well as potential effects of infection on vector population density-on plant virus epidemics. We explore the consequences of preferences that depend on the host (infected or healthy) and vector (viruliferous or nonviruliferous) phenotypes, and how this is affected by the form of transmission, persistent or non-persistent. We show how different components of vector preference have characteristic effects on both the basic reproduction number and the final incidence of disease. We also show how vector preference can induce bistability, in which the virus is able to persist even when it cannot invade from very low densities. Feedbacks between plant infection status, vector population dynamics and virus transmission potentially lead to very complex dynamics, including sustained oscillations. Our work is supported by an interactive interface https://plantdiseasevectorpreference.herokuapp.com/. Our model reiterates the importance of coupling virus infection to vector behaviour, life history and population dynamics to fully understand plant virus epidemics.

The Epidemiology of Xylella fastidiosa; A Perspective on Current Knowledge and Framework to Investigate Plant Host-Vector-Pathogen Interactions.

Insect-transmitted plant diseases caused by viruses, phytoplasmas, and bacteria share many features in common regardless of the causal agent. This perspective aims to show how a model framework, developed originally for plant virus diseases, can be modified for the case of diseases incited by Xylella fastidiosa. In particular, the model framework enables the specification of a simple but quite general invasion criterion defined in terms of key plant, pathogen, and vector parameters and, importantly, their interactions, which determine whether or not an incursion or isolated outbreak of a pathogen will lead to establishment, persistence, and subsequent epidemic development. Hence, this approach is applicable to the wide range of X. fastidiosa-incited diseases that have recently emerged in southern Europe, each with differing host plant, pathogen subspecies, and vector identities. Of particular importance are parameters relating to vector abundance and activity, transmission characteristics, and behavior in relation to preferences for host infection status. Some gaps in knowledge with regard to the developing situation in Europe are noted.

Modeling Virus Coinfection to Inform Management of Maize Lethal Necrosis in Kenya.

Maize lethal necrosis (MLN) has emerged as a serious threat to food security in sub-Saharan Africa. MLN is caused by coinfection with two viruses, Maize chlorotic mottle virus and a potyvirus, often Sugarcane mosaic virus. To better understand the dynamics of MLN and to provide insight into disease management, we modeled the spread of the viruses causing MLN within and between growing seasons. The model allows for transmission via vectors, soil, and seed, as well as exogenous sources of infection. Following model parameterization, we predict how management affects disease prevalence and crop performance over multiple seasons. Resource-rich farmers with large holdings can achieve good control by combining clean seed and insect control. However, crop rotation is often required to effect full control. Resource-poor farmers with smaller holdings must rely on rotation and roguing, and achieve more limited control. For both types of farmer, unless management is synchronized over large areas, exogenous sources of infection can thwart control. As well as providing practical guidance, our modeling framework is potentially informative for other cropping systems in which coinfection has devastating effects. Our work also emphasizes how mathematical modeling can inform management of an emerging disease even when epidemiological information remains scanty. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The evolution of plant virus transmission pathways.

The evolution of plant virus transmission pathways is studied through transmission via seed, pollen, or a vector. We address the questions: under what circumstances does vector transmission make pollen transmission redundant? Can evolution lead to the coexistence of multiple virus transmission pathways? We restrict the analysis to an annual plant population in which reproduction through seed is obligatory. A semi-discrete model with pollen, seed, and vector transmission is formulated to investigate these questions. We assume vector and pollen transmission rates are frequency-dependent and density-dependent, respectively. An ecological stability analysis is performed for the semi-discrete model and used to inform an evolutionary study of trade-offs between pollen and seed versus vector transmission. Evolutionary dynamics critically depend on the shape of the trade-off functions. Assuming a trade-off between pollen and vector transmission, evolution either leads to an evolutionarily stable mix of pollen and vector transmission (concave trade-off) or there is evolutionary bi-stability (convex trade-off); the presence of pollen transmission may prevent evolution of vector transmission. Considering a trade-off between seed and vector transmission, evolutionary branching and the subsequent coexistence of pollen-borne and vector-borne strains is possible. This study contributes to the theory behind the diversity of plant-virus transmission patterns observed in nature.

Proposal of a ranking methodology for plant threats in the EU.

Following a request of the European Commission, EFSA and ANSES, beneficiary of the EFSA tasking grant on horizon scanning for plant pests (GP/EFSA/ALPHA/2017/02), developed a methodology to order by risk non-regulated pests recently identified through the monitoring of media and scientific literature. The ranking methodology proposed at the end of the pilot phase was based on the scoring of pests under evaluation following 16 criteria related to the steps of the pest risk assessment scheme. The multicriteria matrix of scores obtained was then submitted to the multicriteria analysis method PROMETHEE. The pilot methodology was tested on a limited number of pests (14 pests identified during the monitoring activity, and 4 'control' pests whose well-known risk should be reflected either in a positive or negative score), then applied on all non-regulated pests identified through the media and scientific literature monitoring in the first 2 years of the project. After having collected feedback from the targeted final users (EU risk managers), the methodology underwent a few refinements: (i) implementation of the methodology to a set of already assessed reference pests from EFSA opinions, (ii) exclusions of three criteria from the scoring phase, (iii) identification of pests proposed for further action ('positive' pests), using a threshold defined after scoring the reference pests.

Networks in plant epidemiology: from genes to landscapes, countries, and continents.

There is increasing use of networks in ecology and epidemiology, but still relatively little application in phytopathology. Networks are sets of elements (nodes) connected in various ways by links (edges). Network analysis aims to understand system dynamics and outcomes in relation to network characteristics. Many existing natural, social, and technological networks have been shown to have small-world (local connectivity with short-cuts) and scale-free (presence of super-connected nodes) properties. In this review, we discuss how network concepts can be applied in plant pathology from the molecular to the landscape and global level. Wherever disease spread occurs not just because of passive/natural dispersion but also due to artificial movements, it makes sense to superimpose realistic models of the trade in plants on spatially explicit models of epidemic development. We provide an example of an emerging pathosystem (Phytophthora ramorum) where a theoretical network approach has proven particularly fruitful in analyzing the spread of disease in the UK plant trade. These studies can help in assessing the future threat posed by similar emerging pathogens. Networks have much potential in plant epidemiology and should become part of the standard curriculum.

The Epidemiology of Plant Virus Disease: Towards a New Synthesis.

Epidemiology is the science of how disease develops in populations, with applications in human, animal and plant diseases. For plant diseases, epidemiology has developed as a quantitative science with the aims of describing, understanding and predicting epidemics, and intervening to mitigate their consequences in plant populations. Although the central focus of epidemiology is at the population level, it is often necessary to recognise the system hierarchies present by scaling down to the individual plant/cellular level and scaling up to the community/landscape level. This is particularly important for diseases caused by plant viruses, which in most cases are transmitted by arthropod vectors. This leads to range of virus-plant, virus-vector and vector-plant interactions giving a distinctive character to plant virus epidemiology (whilst recognising that some fungal, oomycete and bacterial pathogens are also vector-borne). These interactions have epidemiological, ecological and evolutionary consequences with implications for agronomic practices, pest and disease management, host resistance deployment, and the health of wild plant communities. Over the last two decades, there have been attempts to bring together these differing standpoints into a new synthesis, although this is more apparent for evolutionary and ecological approaches, perhaps reflecting the greater emphasis on shorter often annual time scales in epidemiological studies. It is argued here that incorporating an epidemiological perspective, specifically quantitative, into this developing synthesis will lead to new directions in plant virus research and disease management. This synthesis can serve to further consolidate and transform epidemiology as a key element in plant virus research.

The effect of transmission route on plant virus epidemic development and disease control.

A model for indirect vector transmission and epidemic development of plant viruses is extended to consider direct transmission through vector mating. A basic reproduction number is derived which is the sum of the R(0) values specific for three transmission routes. We analyse the model to determine the effect of direct transmission on plant disease control directed against indirect transmission. Increasing the rate of horizontal sexual transmission means that vector control rate or indirect transmission rate must be increased/decreased substantially to maintain R(0) at a value less than 1. By contrast, proportionately increasing the probability of transovarial transmission has little effect. Expressions are derived for the steady-state values of the viruliferous vector population. There is clear advantage for an insect virus in indirect transmission to plants, especially where the sexual and transovarial transmission rates are low; however information on virulence-transmissibility relationships is required to explain the evolution of a plant virus from an insect virus.

Modelling Vector Transmission and Epidemiology of Co-Infecting Plant Viruses.

Co-infection of plant hosts by two or more viruses is common in agricultural crops and natural plant communities. A variety of models have been used to investigate the dynamics of co-infection which track only the disease status of infected and co-infected plants, and which do not explicitly track the density of inoculative vectors. Much less attention has been paid to the role of vector transmission in co-infection, that is, acquisition and inoculation and their synergistic and antagonistic interactions. In this investigation, a general epidemiological model is formulated for one vector species and one plant species with potential co-infection in the host plant by two viruses. The basic reproduction number provides conditions for successful invasion of a single virus. We derive a new invasion threshold which provides conditions for successful invasion of a second virus. These two thresholds highlight some key epidemiological parameters important in vector transmission. To illustrate the flexibility of our model, we examine numerically two special cases of viral invasion. In the first case, one virus species depends on an autonomous virus for its successful transmission and in the second case, both viruses are unable to invade alone but can co-infect the host plant when prevalence is high.

Pest categorisation of Phymatotrichopsis omnivora.

The Panel on Plant Health performed a pest categorisation of Phymatotrichopsis omnivora, the causal agent of Phymatotrichum root rot of more than 2,000 dicotyledonous plant species, for the EU. The pest is listed as Trechispora brinkmannii in Annex IAI of Directive 2000/29/EC. P. omnivora is a well-defined fungal species and reliable methods exist for its detection and identification. It is present in south-western USA, northern Mexico, Libya and Venezuela. The pest is not known to occur in the EU. P. omnivora has an extremely wide host range; quantitative impacts have been documented for Gossypium spp. (cotton), Medicago sativa (alfalfa), Malus domestica (apple), Prunus persica (peach) and Vitis vinifera (grapevine) as the major cultivated hosts. All major hosts and pathways of entry of the pest into the EU are currently regulated, except for soil and growing media attached or associated with plants originating in Libya. Host availability and climate and edaphic matching suggest that P. omnivora could establish in parts of the EU and further spread mainly by human-assisted means. The pest infects the roots causing wilting and death of its host plants. The introduction of the pest in the EU territory would potentially cause direct and indirect impacts at least to cotton, alfalfa, apple, peach and grapevine production. The main uncertainties concern the host range, the extrapolation to the EU of the climatic and edaphic conditions favouring the disease in some of the infested areas, the role of conidia in the epidemiology of the disease and the magnitude of potential impacts to the EU. P. omnivora meets all the criteria assessed by EFSA for consideration as potential Union quarantine pest. The criteria for considering P. omnivora as a potential Union regulated non-quarantine pest are not met, since the pest is not known to occur in the EU.

Guidance on commodity risk assessment for the evaluation of high risk plants dossiers.

Article 42 of the European Regulation (EU) 2016/2031, on the protective measures against pests of plants, introduces the concept of 'high risk plants, plant products and other objects' that are identified on the basis of a preliminary assessment to be followed by a commodity risk assessment. Following a request of the European Commission, this Guidance was developed to establish the methodology to be followed when performing a commodity risk assessment for high risk commodities (high risk plants, plant products and other objects). The commodity risk assessment performed by EFSA will be based on the information provided by the National Plant Protection Organisations of non-EU countries requesting a lifting of import prohibition of a high risk commodity. Following international standards on pest risk analysis, this Guidance describes a two-step approach for the assessment of pest risk associated with a specified commodity. In the first step, pests, associated with the commodity, that require risk mitigation measures are identified. In the second step, the overall efficacy of proposed risk reduction options for each pest is evaluated. A conclusion on the pest-freedom status of the commodity is achieved. The method requires key uncertainties to be identified.

Adaptation to the cost of resistance in a haploid clonally reproducing organism: the role of mutation, migration and selection.

A model of compensatory evolution with respect to fungicide resistance in a haploid clonally reproducing fungus is developed in which compensatory mutations mitigate fitness costs associated with resistance. The role of mutation, migration and selection in invasion of rare genotypes when the environment changes from unsprayed to sprayed and from sprayed to unsprayed is analysed in detail. In some circumstances (ignoring back mutations) stable internal steady-state values for multiple genotypes can be obtained. In these cases a threshold value (f*) for the fraction of the population exposed to the fungicide can be derived for the transition between different steady-state conditions. Conditions are derived for invasion-when-rare of resistant genotypes at boundary equilibria established sometime after the onset of spraying and conversely of sensitive genotypes sometime after the cessation of spraying are derived. In these cases conditions are presented for (a) the invasion of a resistant genotype with a compensatory mutation (resistant-compensated) into a sensitive-uncompensated population that has re-equilibrated following the onset of spraying and (b) the invasion of a susceptible-uncompensated genotype into a resistant-compensated population that has re-equilibrated following the cessation of spraying, provided certain conditions are met. A resistant-compensated genotype may be fixed (or at near-fixation) in the population following a period of spraying, provided the mean intrinsic growth rate of the resistant-compensated genotype in a sprayed environment (over exposed and non-exposed parts of the population) is greater than that of the susceptible-uncompensated genotype. The fraction of the population exposed (the efficiency of spraying) is critical in this respect. However, it is possible for a sensitive-uncompensated genotype to invade provided there is no fitness gain associated with the resistant-compensated genotype, introduction by migration occurs following equilibration of the population to the new environment, and competitive effects are re-imposed when spraying ceases. We further derive a threshold level for the resident resistant-compensated population to reduce to following the cessation of spraying, such that the introduced susceptible-uncompensated genotype will invade. These results will be of use in determining the long-term persistence of resistance in a pathogen population once a fungicide is no longer effective and removed from use.

Pest categorisation of Aschistonyx eppoi.

The Panel on Plant Health performed a pest categorisation of the gall midge Aschistonyx eppoi Inouye (1964) (Diptera, Cecidomyiidae), for the EU. A. eppoi is a well-defined and distinguishable species, native to Japan and Korea, and recognised as a pest of Juniperus chinensis, although our knowledge is solely based on one unique publication. A. eppoi is absent from the EU, and is listed in Annex IIAI of Directive 2000/29/EC. Its host plants, Juniperus spp. are also listed in Annex III of Directive 2000/29/EC. Plants for planting and branches are considered as pathways for this pest. A. eppoi has been intercepted twice (1974; 1975) in the EU and has been eradicated. The pest is likely to affect bonsai plants of J. chinensis if it were to establish in the EU territory. However, as it is unknown whether A. eppoi would attack the Juniperus spp. that occur in the EU, its potential impact on the wild vegetation is also unknown. As the pest originates from areas with warm climates, impact outdoors would affect the southern parts of the EU. Cultural control (destruction of infested material) and chemical control are the major control methods. All criteria assessed by EFSA for consideration as a potential quarantine pest are met, although there are high uncertainties regarding impact. The species is presently absent from the EU, and thus the criteria for consideration as a potential regulated non-quarantine pest are not met.

Pest categorisation of Unaspis citri.

The Panel on Plant Health performed a pest categorisation of the citrus snow scale, Unaspis citri (Comstock) (Hemiptera: Diaspididae), for the European Union (EU). This is a well-defined and distinguishable species, native to south-eastern Asia, which has spread to many tropical and subtropical regions. U. citri can be a pest of citrus and has been cited on over 28 different species in 16 plant families. In the EU, U. citri occurs in the Azores. There is uncertainty as to whether it occurs in continental Portugal. Reports of it occurring in Greece and Spain are likely to be invalid and based on interception records from these countries. An old Italian record is a misidentification. U. citri is listed in Annex IIAI of 2000/29/EC as a harmful organism. The international trade of hosts, as either plants for planting, fruit or cut flowers, provide potential pathways into the EU. However, current EU legislation prohibits the import of citrus plants for planting from third countries. U. citri is mostly confined to coastal humid tropical areas and does not occur in semi-arid areas that are irrigated. Nevertheless, given that it occurs in the Azores and that there are regional climatic similarities between places where U. citri occurs and climates within the EU, and taking EU host distribution into account, U. citri has the potential to establish in the EU, especially in citrus-growing regions around the Mediterranean where losses in quality and yield of citrus could occur. Phytosanitary measures are available to inhibit the likelihood of introduction of U. citri. Considering the criteria within the remit of EFSA to assess the status as a potential Union quarantine pest (QP), or as a potential regulated non-quarantine pest (RNQP), U. citri meets the criteria assessed by EFSA for consideration as a potential Union QP.

Pest categorisation of Scirtothrips aurantii.

The Panel on Plant Health performed a pest categorisation of the South African citrus thrips, Scirtothrips aurantii Faure (Thysanoptera: Thripidae), for the European Union (EU). This is a well-defined and distinguishable species, recognised as a pest of citrus and mangoes in South Africa, which has been cited on more than 70 different plants, including woody and herbaceous species. It feeds exclusively on young actively growing foliage and fruit. S. aurantii is not known to occur in the EU and is listed in Annex IIAI of 2000/29/EC as a harmful organism presenting a risk to EU plant health. The international trade of hosts as either plants for planting or cut flowers provide potential pathways into the EU. However, current EU legislation prohibits the import of citrus plants. Furthermore, measures aimed at the import of plants for planting in a dormant stage (no young foliage or fruits present) with no soil/growing medium attached, decreases the likelihood of the pest entry with such plants. Interceptions have occurred on Eustoma grandiflorum cut flowers. Considering climatic similarities between some of the countries where S. aurantii occurs (South Africa, Australia) and the EU, its thermal biology and host distribution in the EU, S. aurantii has the potential to establish, especially in citrus-growing regions of the EU. S. aurantii would most probably breed all year long around the Mediterranean and could cause crop losses in citrus, especially oranges. Phytosanitary measures are available to inhibit the introduction of S. aurantii. Considering the criteria within the remit of EFSA to assess its status as a potential Union quarantine pest (QP) or as a potential regulated non-quarantine pest (RNQP), S. aurantii meets with no uncertainties the criteria assessed by EFSA for consideration as a potential Union QP.

Pest categorisation of Scirtothrips citri.

The Panel on Plant Health performed a pest categorisation of the citrus thrips, Scirtothrips citri (Moulton) (Thysanoptera: Thripidae), for the European Union (EU). This is a well-defined and distinguishable species, occurring in North America and Asia. Its precise distribution in Asia is uncertain. S. citri is a pest of citrus and blueberries and has been cited on over 50 different host species in 33 plant families. Whether all plants reported as hosts are true hosts, allowing population development of S. citri, is uncertain. S. citri feeds exclusively on young actively growing foliage and fruit. It is not known to occur in the EU and is listed in Annex IIAI of 2000/29/EC as a harmful organism. The international trade of hosts, as either plants for planting or cut flowers, provide potential pathways into the EU. However, current EU legislation prohibits the import of citrus plants for planting. Furthermore, measures aimed at the import of plants for planting in a dormant stage (no young foliage or fruits present) with no soil/growing medium attached, decreases the likelihood of the pest's entry via other hosts. Considering that there are regional climatic similarities where S. citri occurs in the USA with climates in the EU, and taking EU host distribution into account, S. citri has the potential to establish in the EU, especially in citrus and blueberry growing regions around the Mediterranean where quality losses in citrus and yield losses in blueberry could occur. Phytosanitary measures are available to inhibit the likelihood of introduction of S. citri from infested countries. Considering the criteria within the remit of EFSA to assess its status as a potential Union quarantine pest (QP) or as a potential regulated non-quarantine pest (RNQP), S. citri meets with no uncertainties the criteria assessed by EFSA for consideration as a potential Union QP.