Scientific Opinion on the Risks to Plant Health Posed by Xylella Fastidiosa in the EU Territory, with the Identification and Evaluation of Risk Reduction Options. Baker, R., Bragard, C., Caffier, D., Candresse, T., Gilioli, G., Grégoire, J., Holb, I., Jeger, M. J., Karadjova, O. E., Magnusson, C., Makowski, D., Manceau, C., Navajas, M., Rafoss, T., Rossi, V., Schans, J., Schrader, G., Urek, G., Vloutoglou, I., Winter, S., & van der Werf, W. 13(1):3989+.
Scientific Opinion on the Risks to Plant Health Posed by Xylella Fastidiosa in the EU Territory, with the Identification and Evaluation of Risk Reduction Options [link]Paper  doi  abstract   bibtex   
[Abstract] The EFSA Panel on Plant Health conducted a pest risk assessment and an evaluation of risk reduction options for Xylella fastidiosa. X. fastidiosa has been detected in olive in the EU with a distribution restricted to the region of Apulia in Italy and is under official control. X. fastidiosa has a very broad host range, including many common cultivated and wild plants. All xylem fluid-feeding insects in Europe are considered to be potential vectors. Philaenus spumarius (Hemiptera: Aphrophoridae), a polyphagous spittlebug widespread in the whole risk assessment area, has been identified as a vector in Apulia. The probability of entry of X. fastidiosa from countries where X. fastidiosa is reported is very high with plants for planting and moderate with infectious insect vectors carried with plant commodities or travelling as stowaways. Establishment and spread in the EU is very likely. The consequences are considered to be major because yield losses and other damage would be high and require costly control measures. The systematic use of insecticides for vector control may create environmental impacts. With regard to risk reduction options, strategies for the prevention of introduction and for the containment of outbreaks should focus on the two main pathways (plants for planting and infectious insect vectors) and combine the most effective options in an integrated approach. For plants for planting, these could be pest-free production areas, surveillance, certification, screened greenhouse production, vector control and testing for infection and, for some plant species, treatments (e.g. thermotherapy). To prevent entry of the infectious vectors, insecticide treatments and inspection of consignments and production sites are required. The Panel has also reviewed the effectiveness of risk reduction options for X. fastidiosa and its vectors listed in Directive 2000/29/EC and in the EU emergency measures. The Panel recommends the continuation and intensification of research on the host range, epidemiology and control of the Apulian outbreak. [:Excerpt adapted from the Summary (heading added for better readability)] Following a request from the European Commission, the EFSA Panel on Plant Health was asked to deliver a scientific opinion on the pest risk posed by Xylella fastidiosa for the European Union territory and to identify risk management options and evaluate their effectiveness in reducing the risk to plant health posed by the organism. In particular, the Panel was asked to provide an opinion on the effectiveness of the current EU requirements against X. fastidiosa, which are laid down in Council Directive 2000/29/EC and the EU emergency measures against X. fastidiosa (Decision 2014/497/EU), in reducing the risk of introduction of this pest into, and its spread within, the EU territory. The current distribution of X. fastidiosa in the EU is restricted to one strain within one province of the Apulia region in south Italy, where several thousand hectares of olive plantations are affected, and it is under official control. X. fastidiosa is also reported in Apulia on Prunus cerasifera, Prunus dulcis, Nerium oleander, Acacia saligna, Polygala myrtifolia, Westringia fruticosa, Spartium junceum and Vinca spp. The genotype of X. fastidiosa of the Apulian outbreak has been attributed to the subspecies pauca. Nevertheless, this pest risk assessment considers all subspecies of X. fastidiosa. [::Risk to the EU territory] X. fastidiosa presents a major risk to the EU territory because it has the potential to cause disease in the risk assessment area once it establishes, as hosts are present and the environmental conditions are favourable. X. fastidiosa may affect several crops in Europe, such as citrus, grapevine and stone fruits (almond, peach, plum), but also several tree and ornamental plants, for example oak, sycamore and oleander. X. fastidiosa has a very broad host range, including many cultivated and wild plants common in Europe. There is some host differentiation between the generally accepted four subspecies of X. fastidiosa with regard to symptomatic hosts; there is, however, high uncertainty with regard to the potential host range of X. fastidiosa in the European flora as a wide range of European wild plant species have never been exposed to the bacterium and it is not known whether they would be hosts, and, if so, whether they would be symptomatic or asymptomatic. All xylem fluid-feeding insects in Europe are considered to be potential vectors. Members of the families Cicadellidae, Aphrophoridae and Cercopidae are vectors in the Americas and, hence, should be considered to be potential vectors in Europe. The Cicadidae and Tibicinidae should also be considered potential vectors. The hemipteran Philaenus spumarius has been identified as a vector in Apulia, Italy. With regard to the assessment of the risk to plant health for the EU territory, the conclusions are as follows: [::Probability of entry] The probability of entry for plants for planting from countries where X. fastidiosa is reported is rated very likely because: [::] The association with the pathway at origin is rated as very likely for plants for planting because (1) plants for planting have been found to be a source of the bacterium for outbreaks, (2) host plants can be asymptomatic and often remain undetected, (3) a very large number of plant species are recorded as hosts and (4) very high quantities of plants for planting are imported from countries where X. fastidiosa is reported. [::] The ability of the bacteria surviving during transport is very likely. [::] The probability of the pest surviving any existing management procedure is very likely. [::] Additionally, the probability of transfer to a suitable host is rated as very likely, based on the intended use of the plant material for planting (rootstocks) or grafting (scions, budwood) and because host plants are extensively present in the risk assessment area. Insect vectors are also distributed throughout the risk assessment area. [\n] The likelihood of entry for the infectious insect vectors is moderately likely because the pest: [::] is often associated with the pathway at the origin; [::] is moderately able to survive during transport or storage; [::] is affected by the current pest management procedures existing in the risk assessment area; [::] has some limitations for transfer to a suitable host in the risk assessment area. [\n] Entry is considered to have medium uncertainty because the distribution of X. fastidiosa in the countries of origin is not fully known, knowledge of host plant susceptibility is only partial and only a few interceptions of infected plants have been made, taking into account also the difficulty of detecting contaminated but asymptomatic plants. The difficulties in assessing precisely the quantities of plants for planting imported within the EU are also a matter of uncertainty. Additionally, only limited data are available on vectors' capacity to survive long-distance transportation on their own in vehicles and they are restricted to only one species, Homalodisca vitripennis. Similarly, only limited data are available on vectors' autonomous dispersal capacity, and they concern only H. vitripennis. There are no data in the EUROPHYT database on the interception of vectors. [::Probability of establishment] The probability of establishment, following an entry of X. fastidiosa, is rated as very likely, based on the very high probability that the pathogen will find a suitable host owing to the very large range of host plants and potential host plants, and to the wide distribution and polyphagy of known and potential vectors. Other elements taken into account are the high probability of finding a climatically suitable environment with few adverse abiotic factors and no known effective natural enemies of X. fastidiosa. The information available regarding winter recovery in infected plants mostly relates to grapevine and the subspecies fastidiosa. The lack of effective cultural practices or control measures also increases the probability of establishment. [\n] The uncertainty level for establishment is rated as low, based on the fact that X. fastidiosa is already reported in Apulia. There is no uncertainty regarding the availability of a wide range of host plants, but questions remain regarding the susceptibility of the indigenous European flora. There is one confirmed vector species (P. spumarius) that is widespread, abundant and polyphagous; a large range of additional potential vectors has yet to be studied. Suitable climates are available in the risk assessment area. There is a lack of data regarding the overwintering capacity at low temperature and, more generally, regarding the range of temperatures over which the bacteria can thrive, and this makes it very difficult to assess the northernmost limit to its distribution in the EU. [::Probability of spread] The probability of spread from established infestations of X. fastidiosa is rated as very likely because of the large number of confirmed or potential host plants and the abundance and widespread distribution of known (P. spumarius) or potential vectors. Spread over short to long distances by human assistance is very likely: this may occur via infected plants for planting or by passive transport of infectious insects in vehicles. Infectious vectors may spread locally by flying or be passively transported longer distances by wind. [\n] Concerning the spread, uncertainty is rated as medium. The contributions of human- and windmediated spread mechanisms are still uncertain. There is a lack of data on how far the insect vectors can fly. There is also a lack of precise indications on how current farming practices could have an impact on potential insect vectors and limit the spread of the disease. [::Potential consequences] The overall potential consequences of X. fastidiosa in the European territory are rated as major considering the severe losses on olive in the Apulian outbreak, on citrus in South America and on grapes in North America. In commercial crops, when conditions are suitable for symptom expression and efficient insect vectors are present, yield losses and damage would be high and imply costly control measures. The disease also has a negative social impact since it is not readily controllable in smallholdings and family gardens. Depending on the host range of the X. fastidiosa subspecies introduced, major crops, ornamental plants or forest trees could be affected, as in other areas of the world. In addition to these elements, the use of insecticide may have environmental impacts. Breeding and nursery activities might also be affected. [\n] The uncertainty for the consequences is rated as low, based on a worst-case scenario approach. The exact host range of a given strain, the lack of knowledge on the potential vectors in the risk assessment area and the agro-ecological complexity of the diseases shall nevertheless be taken into account. [::Risk reduction options] With regard to risk reduction options, the Panel reached the following conclusions. A thorough review of the literature yielded no indication that eradication is a successful option once the disease is established in an area. Past attempts, in Taiwan and in Brazil, proved unsuccessful, probably because of the broad host range of the pathogen and its vectors. Therefore, the priority should be to prevent introduction. Strategies for preventing the introduction from areas where the pathogen is present and for the containment of outbreaks should focus on the two main pathways (plants for planting and infectious insects) and be based on an integrated system approach, combining, when applicable, the most effective options (e.g. pest-free areas, surveillance, certification, screen house production, control of vectors and testing for plant propagation material, preparation, treatment and inspection of consignments for the pathway of the infectious vectors). [\n] For the plants for planting pathway, some risk reduction options have been considered to be more effective at reducing the likelihood of introduction of X. fastidiosa and/or infective insect vectors: [::] Prohibiting the import of X. fastidiosa host species plants for planting would be highly effective but its application would be constrained by the very wide potential host range of this pathogen and the large trade volumes. This is, however, a feasible option for high-risk commodities. [::] Limiting the import of plants for planting to pest-free areas of origin is considered to be highly effective, but pest-free production sites are assessed as having lower effectiveness unless combined with other measures (e.g. screen house production, certification and testing, vector control) in an integrated approach. [::] Certification schemes, growing plants under exclusion conditions and vector control in nurseries have high effectiveness, particularly when combined in an integrated approach. [::] Among consignment treatments, the thermotherapy of dormant plants has been applied effectively to control X. fastidiosa in grapevine plants for planting. This practice is already applied to control other pathogens in Vitis plant propagation material. The import of dormant plants for planting is also effective in preventing the introduction of exotic sharpshooter vectors species that lay eggs only on leaves or green tissues, but it is not effective against the sharpshooters that lay eggs on wood, unless combined with thermotherapy. [::] Specific insecticide treatments of consignments of plants for planting can effectively reduce the likelihood of infective insect vectors being carried together with traded plants. [\n] For the infective insect vectors, the likelihood of entry with other plant material such as cut flowers or green foliage can be reduced by appropriate treatment of the consignments and by an integrated approach in production sites free of X. fastidiosa. [\n] The Panel has also reviewed the effectiveness of risk reduction options for X. fastidiosa and its vectors listed in the Directive 2000/29/EC4 and in EU Implementing Decision 2014/497/EU5 for this pathogen. [\n] With regard to Directive 2000/29/EC, the Panel concluded that: [::] The prohibition of introduction of Citrus, Fortunella, Poncirus and their hybrids, other than fruit and seeds, and Vitis, other than fruit, originating in third countries is an effective measure to prevent the introduction of X. fastidiosa with these species from countries where X. fastidiosa is present. However, restrictions on the introduction of Prunus do not reduce the risks of introduction of X. fastidiosa since Prunus plants free from leaves, flower and fruit can still be imported and harbour the bacterium. Furthermore, many other host plants can still be imported and may carry the bacterium, as shown by the recently documented introductions of coffee plants that harbour X. fastidiosa. [::] The exemption from official registration for small producers whose entire production and sale of relevant plants are intended for final use by persons on the local market and who are not professionally involved in plant production could facilitate the local dissemination of the pathogenic agent considering the very wide host range of X. fastidiosa. [\n] With regard to Implementing Decision 2014/497/EU, the Panel concluded that: [::] The exemption of seeds is scientifically justified. [::] There is very high uncertainty on the host range of the strain of X. fastidiosa occurring in Apulia because research is still ongoing. More generally, the host range of X. fastidiosa is still uncertain. It is very likely that the bacterium has a wider host range than the species listed in the emergency measures. Nevertheless, some of the already known host plants of the Apulian strain are not mentioned in the implementing decision (i.e. plants of the genera Acacia, Polygala, Spartium and Westringia). [::] The reinforcement of conditions for imports from third countries is assessed as effective, but only some genera of host plants are included (Catharanthus, Nerium, Olea, Prunus, Vinca, Malva, Portulaca, Quercus and Sorghum), which mitigates the effectiveness of that measure. [::] There is a need for detailed and harmonised protocols for survey, sampling and testing, with at least guidelines regarding minimum requirements to be achieved in demarcated areas, buffer zones and areas not known to be infected. [::] Asymptomatic hosts, asymptomatic infections or low infections can escape surveys based solely on visual inspection and even based on laboratory tests as early infections or heterogeneous distribution of the bacterium in the plant may lead to false-negative results. [::] There is a need to reduce the infectious insect vector populations (e.g. by vector control, vegetation management, inoculum reduction by removal of infected plants) in the outbreak area and to prevent their movement from infected plants. Special care is necessary when removing infected plants or weeds, for instance, as this may result in movement of infectious insect vectors. [::] The ban on planting of ” specified plants” in demarcated areas is appropriate, but all known host plants should be considered. [::] Public awareness of diseases that can infect plants in gardens or natural or unmanaged environments is important, and awareness-raising activities should be organised for all people in demarcated areas or buffer zones and their vicinity. [::Future research] The Panel recommends the continuation and intensification of research activities on the host range, epidemiology and control of the Apulian outbreak of X. fastidiosa. Based on the knowledge acquired by this research, uncertainties could be substantially reduced and a more thorough assessment of the risk and of the mitigation measures could be conducted for the Apulian strain of X. fastidiosa.
@article{bakerScientificOpinionRisks2015,
  title = {Scientific {{Opinion}} on the Risks to Plant Health Posed by {{Xylella}} Fastidiosa in the {{EU}} Territory, with the Identification and Evaluation of Risk Reduction Options},
  author = {Baker, Richard and Bragard, Claude and Caffier, David and Candresse, Thierry and Gilioli, Gianni and Grégoire, Jean-Claude and Holb, Imre and Jeger, Michael J. and Karadjova, Olia E. and Magnusson, Christer and Makowski, David and Manceau, Charles and Navajas, Maria and Rafoss, Trond and Rossi, Vittorio and Schans, Jan and Schrader, Gritta and Urek, Gregor and Vloutoglou, Irene and Winter, Stephan and van der Werf, Wopke},
  date = {2015-01},
  journaltitle = {EFSA Journal},
  volume = {13},
  pages = {3989+},
  doi = {10.2903/j.efsa.2015.3989},
  url = {https://doi.org/10.2903/j.efsa.2015.3989},
  abstract = {[Abstract] The EFSA Panel on Plant Health conducted a pest risk assessment and an evaluation of risk reduction options for Xylella fastidiosa. X. fastidiosa has been detected in olive in the EU with a distribution restricted to the region of Apulia in Italy and is under official control. X. fastidiosa has a very broad host range, including many common cultivated and wild plants. All xylem fluid-feeding insects in Europe are considered to be potential vectors. Philaenus spumarius (Hemiptera: Aphrophoridae), a polyphagous spittlebug widespread in the whole risk assessment area, has been identified as a vector in Apulia. The probability of entry of X. fastidiosa from countries where X. fastidiosa is reported is very high with plants for planting and moderate with infectious insect vectors carried with plant commodities or travelling as stowaways. Establishment and spread in the EU is very likely. The consequences are considered to be major because yield losses and other damage would be high and require costly control measures. The systematic use of insecticides for vector control may create environmental impacts. With regard to risk reduction options, strategies for the prevention of introduction and for the containment of outbreaks should focus on the two main pathways (plants for planting and infectious insect vectors) and combine the most effective options in an integrated approach. For plants for planting, these could be pest-free production areas, surveillance, certification, screened greenhouse production, vector control and testing for infection and, for some plant species, treatments (e.g. thermotherapy). To prevent entry of the infectious vectors, insecticide treatments and inspection of consignments and production sites are required. The Panel has also reviewed the effectiveness of risk reduction options for X. fastidiosa and its vectors listed in Directive 2000/29/EC and in the EU emergency measures. The Panel recommends the continuation and intensification of research on the host range, epidemiology and control of the Apulian outbreak.

[:Excerpt adapted from the Summary (heading added for better readability)] Following a request from the European Commission, the EFSA Panel on Plant Health was asked to deliver a scientific opinion on the pest risk posed by Xylella fastidiosa for the European Union territory and to identify risk management options and evaluate their effectiveness in reducing the risk to plant health posed by the organism. In particular, the Panel was asked to provide an opinion on the effectiveness of the current EU requirements against X. fastidiosa, which are laid down in Council Directive 2000/29/EC and the EU emergency measures against X. fastidiosa (Decision 2014/497/EU), in reducing the risk of introduction of this pest into, and its spread within, the EU territory. The current distribution of X. fastidiosa in the EU is restricted to one strain within one province of the Apulia region in south Italy, where several thousand hectares of olive plantations are affected, and it is under official control. X. fastidiosa is also reported in Apulia on Prunus cerasifera, Prunus dulcis, Nerium oleander, Acacia saligna, Polygala myrtifolia, Westringia fruticosa, Spartium junceum and Vinca spp. The genotype of X. fastidiosa of the Apulian outbreak has been attributed to the subspecies pauca. Nevertheless, this pest risk assessment considers all subspecies of X. fastidiosa. 

[::Risk to the EU territory] X. fastidiosa presents a major risk to the EU territory because it has the potential to cause disease in the risk assessment area once it establishes, as hosts are present and the environmental conditions are favourable. X. fastidiosa may affect several crops in Europe, such as citrus, grapevine and stone fruits (almond, peach, plum), but also several tree and ornamental plants, for example oak, sycamore and oleander. X. fastidiosa has a very broad host range, including many cultivated and wild plants common in Europe. There is some host differentiation between the generally accepted four subspecies of X. fastidiosa with regard to symptomatic hosts; there is, however, high uncertainty with regard to the potential host range of X. fastidiosa in the European flora as a wide range of European wild plant species have never been exposed to the bacterium and it is not known whether they would be hosts, and, if so, whether they would be symptomatic or asymptomatic. All xylem fluid-feeding insects in Europe are considered to be potential vectors. Members of the families Cicadellidae, Aphrophoridae and Cercopidae are vectors in the Americas and, hence, should be considered to be potential vectors in Europe. The Cicadidae and Tibicinidae should also be considered potential vectors. The hemipteran Philaenus spumarius has been identified as a vector in Apulia, Italy. With regard to the assessment of the risk to plant health for the EU territory, the conclusions are as follows: 

[::Probability of entry] The probability of entry for plants for planting from countries where X. fastidiosa is reported is rated very likely because: [::] The association with the pathway at origin is rated as very likely for plants for planting because (1) plants for planting have been found to be a source of the bacterium for outbreaks, (2) host plants can be asymptomatic and often remain undetected, (3) a very large number of plant species are recorded as hosts and (4) very high quantities of plants for planting are imported from countries where X. fastidiosa is reported. [::] The ability of the bacteria surviving during transport is very likely. [::] The probability of the pest surviving any existing management procedure is very likely. [::] Additionally, the probability of transfer to a suitable host is rated as very likely, based on the intended use of the plant material for planting (rootstocks) or grafting (scions, budwood) and because host plants are extensively present in the risk assessment area. Insect vectors are also distributed throughout the risk assessment area. 

[\textbackslash n] The likelihood of entry for the infectious insect vectors is moderately likely because the pest: [::] is often associated with the pathway at the origin; [::] is moderately able to survive during transport or storage; [::] is affected by the current pest management procedures existing in the risk assessment area; [::] has some limitations for transfer to a suitable host in the risk assessment area. 

[\textbackslash n] Entry is considered to have medium uncertainty because the distribution of X. fastidiosa in the countries of origin is not fully known, knowledge of host plant susceptibility is only partial and only a few interceptions of infected plants have been made, taking into account also the difficulty of detecting contaminated but asymptomatic plants. The difficulties in assessing precisely the quantities of plants for planting imported within the EU are also a matter of uncertainty. Additionally, only limited data are available on vectors' capacity to survive long-distance transportation on their own in vehicles and they are restricted to only one species, Homalodisca vitripennis. Similarly, only limited data are available on vectors' autonomous dispersal capacity, and they concern only H. vitripennis. There are no data in the EUROPHYT database on the interception of vectors. [::Probability of establishment] The probability of establishment, following an entry of X. fastidiosa, is rated as very likely, based on the very high probability that the pathogen will find a suitable host owing to the very large range of host plants and potential host plants, and to the wide distribution and polyphagy of known and potential vectors. Other elements taken into account are the high probability of finding a climatically suitable environment with few adverse abiotic factors and no known effective natural enemies of X. fastidiosa. The information available regarding winter recovery in infected plants mostly relates to grapevine and the subspecies fastidiosa. The lack of effective cultural practices or control measures also increases the probability of establishment.

[\textbackslash n] The uncertainty level for establishment is rated as low, based on the fact that X. fastidiosa is already reported in Apulia. There is no uncertainty regarding the availability of a wide range of host plants, but questions remain regarding the susceptibility of the indigenous European flora. There is one confirmed vector species (P. spumarius) that is widespread, abundant and polyphagous; a large range of additional potential vectors has yet to be studied. Suitable climates are available in the risk assessment area. There is a lack of data regarding the overwintering capacity at low temperature and, more generally, regarding the range of temperatures over which the bacteria can thrive, and this makes it very difficult to assess the northernmost limit to its distribution in the EU.

[::Probability of spread] The probability of spread from established infestations of X. fastidiosa is rated as very likely because of the large number of confirmed or potential host plants and the abundance and widespread distribution of known (P. spumarius) or potential vectors. Spread over short to long distances by human assistance is very likely: this may occur via infected plants for planting or by passive transport of infectious insects in vehicles. Infectious vectors may spread locally by flying or be passively transported longer distances by wind.

[\textbackslash n] Concerning the spread, uncertainty is rated as medium. The contributions of human- and windmediated spread mechanisms are still uncertain. There is a lack of data on how far the insect vectors can fly. There is also a lack of precise indications on how current farming practices could have an impact on potential insect vectors and limit the spread of the disease.

[::Potential consequences] The overall potential consequences of X. fastidiosa in the European territory are rated as major considering the severe losses on olive in the Apulian outbreak, on citrus in South America and on grapes in North America. In commercial crops, when conditions are suitable for symptom expression and efficient insect vectors are present, yield losses and damage would be high and imply costly control measures. The disease also has a negative social impact since it is not readily controllable in smallholdings and family gardens. Depending on the host range of the X. fastidiosa subspecies introduced, major crops, ornamental plants or forest trees could be affected, as in other areas of the world. In addition to these elements, the use of insecticide may have environmental impacts. Breeding and nursery activities might also be affected.

[\textbackslash n] The uncertainty for the consequences is rated as low, based on a worst-case scenario approach. The exact host range of a given strain, the lack of knowledge on the potential vectors in the risk assessment area and the agro-ecological complexity of the diseases shall nevertheless be taken into account.

[::Risk reduction options] With regard to risk reduction options, the Panel reached the following conclusions. A thorough review of the literature yielded no indication that eradication is a successful option once the disease is established in an area. Past attempts, in Taiwan and in Brazil, proved unsuccessful, probably because of the broad host range of the pathogen and its vectors. Therefore, the priority should be to prevent introduction. Strategies for preventing the introduction from areas where the pathogen is present and for the containment of outbreaks should focus on the two main pathways (plants for planting and infectious insects) and be based on an integrated system approach, combining, when applicable, the most effective options (e.g. pest-free areas, surveillance, certification, screen house production, control of vectors and testing for plant propagation material, preparation, treatment and inspection of consignments for the pathway of the infectious vectors).

[\textbackslash n] For the plants for planting pathway, some risk reduction options have been considered to be more effective at reducing the likelihood of introduction of X. fastidiosa and/or infective insect vectors: [::] Prohibiting the import of X. fastidiosa host species plants for planting would be highly effective but its application would be constrained by the very wide potential host range of this pathogen and the large trade volumes. This is, however, a feasible option for high-risk commodities. [::] Limiting the import of plants for planting to pest-free areas of origin is considered to be highly effective, but pest-free production sites are assessed as having lower effectiveness unless combined with other measures (e.g. screen house production, certification and testing, vector control) in an integrated approach. [::] Certification schemes, growing plants under exclusion conditions and vector control in nurseries have high effectiveness, particularly when combined in an integrated approach. [::] Among consignment treatments, the thermotherapy of dormant plants has been applied effectively to control X. fastidiosa in grapevine plants for planting. This practice is already applied to control other pathogens in Vitis plant propagation material. The import of dormant plants for planting is also effective in preventing the introduction of exotic sharpshooter vectors species that lay eggs only on leaves or green tissues, but it is not effective against the sharpshooters that lay eggs on wood, unless combined with thermotherapy. [::] Specific insecticide treatments of consignments of plants for planting can effectively reduce the likelihood of infective insect vectors being carried together with traded plants.

[\textbackslash n] For the infective insect vectors, the likelihood of entry with other plant material such as cut flowers or green foliage can be reduced by appropriate treatment of the consignments and by an integrated approach in production sites free of X. fastidiosa.

[\textbackslash n] The Panel has also reviewed the effectiveness of risk reduction options for X. fastidiosa and its vectors listed in the Directive 2000/29/EC4 and in EU Implementing Decision 2014/497/EU5 for this pathogen.

[\textbackslash n] With regard to Directive 2000/29/EC, the Panel concluded that: [::] The prohibition of introduction of Citrus, Fortunella, Poncirus and their hybrids, other than fruit and seeds, and Vitis, other than fruit, originating in third countries is an effective measure to prevent the introduction of X. fastidiosa with these species from countries where X. fastidiosa is present. However, restrictions on the introduction of Prunus do not reduce the risks of introduction of X. fastidiosa since Prunus plants free from leaves, flower and fruit can still be imported and harbour the bacterium. Furthermore, many other host plants can still be imported and may carry the bacterium, as shown by the recently documented introductions of coffee plants that harbour X. fastidiosa. [::] The exemption from official registration for small producers whose entire production and sale of relevant plants are intended for final use by persons on the local market and who are not professionally involved in plant production could facilitate the local dissemination of the pathogenic agent considering the very wide host range of X. fastidiosa.

[\textbackslash n] With regard to Implementing Decision 2014/497/EU, the Panel concluded that: [::] The exemption of seeds is scientifically justified. [::] There is very high uncertainty on the host range of the strain of X. fastidiosa occurring in Apulia because research is still ongoing. More generally, the host range of X. fastidiosa is still uncertain. It is very likely that the bacterium has a wider host range than the species listed in the emergency measures. Nevertheless, some of the already known host plants of the Apulian strain are not mentioned in the implementing decision (i.e. plants of the genera Acacia, Polygala, Spartium and Westringia). [::] The reinforcement of conditions for imports from third countries is assessed as effective, but only some genera of host plants are included (Catharanthus, Nerium, Olea, Prunus, Vinca, Malva, Portulaca, Quercus and Sorghum), which mitigates the effectiveness of that measure. [::] There is a need for detailed and harmonised protocols for survey, sampling and testing, with at least guidelines regarding minimum requirements to be achieved in demarcated areas, buffer zones and areas not known to be infected. [::] Asymptomatic hosts, asymptomatic infections or low infections can escape surveys based solely on visual inspection and even based on laboratory tests as early infections or heterogeneous distribution of the bacterium in the plant may lead to false-negative results. [::] There is a need to reduce the infectious insect vector populations (e.g. by vector control, vegetation management, inoculum reduction by removal of infected plants) in the outbreak area and to prevent their movement from infected plants. Special care is necessary when removing infected plants or weeds, for instance, as this may result in movement of infectious insect vectors. [::] The ban on planting of ” specified plants” in demarcated areas is appropriate, but all known host plants should be considered. [::] Public awareness of diseases that can infect plants in gardens or natural or unmanaged environments is important, and awareness-raising activities should be organised for all people in demarcated areas or buffer zones and their vicinity.

[::Future research] The Panel recommends the continuation and intensification of research activities on the host range, epidemiology and control of the Apulian outbreak of X. fastidiosa. Based on the knowledge acquired by this research, uncertainties could be substantially reduced and a more thorough assessment of the risk and of the mitigation measures could be conducted for the Apulian strain of X. fastidiosa.},
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  number = {1},
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}
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