Alan MacLeod

Evolution of the international regulation of plant pests and challenges for future plant health

Plant pathogens and invertebrates harmful to plants, collectively referred to as plant pests, continue to threaten food security. International cooperation and regulatory systems to inhibit the spread of plant pests began formally in 1878. Initially seven countries worked together and agreed phytosanitary measures against grape phylloxera, Phylloxera vastatrix (=Daktulosphaira vitifoliae). There are now 172 countries that are contracting parties to the International Plant Protection Convention, a treaty that aims to prevent the introduction and spread of pests of plants and plant products, and to promote appropriate measures for their control. Apparently contradictory interests between international trade, which has facilitated the spread of plant pests, and the protection of plants are mutually recognised in global trade and phytosanitary agreements. The principle that risk management measures should provide an appropriate level of protection without undue interference in trade was established within the plant protection agreements at the beginning of the 20th Century and is still fundamental to risk management policy today. Globally ten Regional Plant Protection Organizations facilitate more local cooperation and recommend the regulation of over 1,000 named quarantine plant pests. Member States of the European Union work together and regulate imported plant material on the grounds of plant health with each Member State taking into account the plant health concerns of every other Member State. However, decision making can be slow and border inspections poorly targeted. Close relationships between regulatory scientists and policy makers, focussed on agricultural and horticultural production, are changing to take a broader stakeholder community into consideration as decisions regarding the environment seek to draw upon a wider knowledge base. Challenges that impede the success of limiting international pest movement include increased international trade and climate change. International guidelines designed to prevent pest spread present challenges of their own if they remain difficult to implement.

Eliciting and Combining Decision Criteria Using a Limited Palette of Utility Functions and Uncertainty Distributions: Illustrated by Application to Pest Risk Analysis.

Utility functions in the form of tables or matrices have often been used to combine discretely rated decision-making criteria. Matrix elements are usually specified individually, so no one rule or principle can be easily stated for the utility function as a whole. A series of five matrices are presented that aggregate criteria two at a time using simple rules that express a varying degree of constraint of the lower rating over the higher. A further nine possible matrices were obtained by using a different rule either side of the main axis of the matrix to describe situations where the criteria have a differential influence on the outcome. Uncertainties in the criteria are represented by three alternative frequency distributions from which the assessors select the most appropriate. The output of the utility function is a distribution of rating frequencies that is dependent on the distributions of the input criteria. In pest risk analysis (PRA), seven of these utility functions were required to mimic the logic by which assessors for the European and Mediterranean Plant Protection Organization arrive at an overall rating of pest risk. The framework enables the development of PRAs that are consistent and easy to understand, criticize, compare, and change. When tested in workshops, PRA practitioners thought that the approach accorded with both the logic and the level of resolution that they used in the risk assessments.

The role of regulatory mechanisms for control of plant diseases and food security—case studies from potato production in Britain

Being aware of the potentially devastating impacts of plant diseases on food security, governments have designed and employ plant health legislation to prevent or inhibit the worst impacts. The development of such policies in Britain, and latterly in Europe, can be closely linked to disease events that have occurred in the potato sector. We analyse early and current examples of policies governing potato diseases in Britain to identify the decision processes leading to the implementation of such phytosanitary policies and how they have evolved over time and in response to different disease threats. Reasons for developing and implementing phytosanitary policies include the desire to prevent pathogens being introduced (entering and establishing in a new area), the protection of export markets, and the lack of effective control measures. Circumstances in which regulatory policies would not be appropriate could include situations where a disease is already widely distributed, unacceptable costs, lack of exclusion measures, or difficulties of disease diagnosis. We conclude that in general, government policies have worked well in protecting British potato growing over the last one hundred years, despite of the failures of some of the policies discussed here. They have also contributed much to the development of plant health policies for other crops. Voluntary grower initiatives are a new mechanism complementing existing formal policies with an additional level of security that allows individual growers to take on additional responsibility rather than relying entirely on government legislation.

Valuing marine parks in a small island developing state: a travel cost analysis in Seychelles

A major problem facing the Seychelles islands is the decline in the quality and the value of marine protected areas (MPAs). Economic valuation can help guide policy makers to understand the value of marine resources and the cost of neglecting MPAs by expressing the value of their goods and services in monetary terms. This paper presents an analysis of the economic value of a group of marine parks in Seychelles. The travel cost method is used to establish willingness-to-pay of international tourists for trips to marine parks in Seychelles from their observed behaviour. The average per-trip consumer surplus is approximately €128 for single-site visitors and €65 for multiple-site visitors. The total social welfare value attributable to the recreational opportunity in marine parks is approximately €3.7 million annually. These results provide policy makers with a strong justification for government investment needed to maintain marine sites in Seychelles.

Pest risk assessment of Atropellis spp. for the EU territory

Abstract Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a risk assessment for Atropellis spp. in the EU focusing on the risk of entry, the host range and the potential impacts. Atropellis is a fungal pathogen of several Pinus spp. in North America. The pathogen has not been reported from Europe and is a quarantine pest regulated in Annex IIAI of Council Directive 2000/29/EC on plants (other than fruit and seeds), isolated bark and wood of Pinus. The main pathways of entry considered were Pinus plants, wood and isolated bark. Given the ban of importing Pinus plants from outside Europe into the EU and the lack of information on EU imports of isolated Pinus bark, only the wood pathway was assessed quantitatively. The conclusion of the assessment of entry for scenario A0 (current regulatory situation) is that the risk of entry of Atropellis spp. is close to zero. This conclusion is expected to apply also in the case of removing the specific Atropellis regulations, because of the remaining generic Pinus requirements, as well as in a scenario with additional risk reduction options. The uncertainty associated with this assessment is relatively limited, given that all the quartiles of the estimated distribution of the number of potential founder populations are close to zero. For the North American Pinus spp. known to be susceptible and widely planted in the EU (mainly P. contorta and P. strobus), the damage observed in North America (loss of wood quality, stem deformations, mortality in young stands, environmental consequences) is expected in the EU to a similar (or higher) degree, should the pathogen be introduced. Similar impacts are expected on the European Pinus spp. known to be host of Atropellis spp. These include widespread and locally abundant species such as P. nigra, P. sylvestris and P. pinaster. There are, however, large uncertainties associated with this impact assessment due to the unknown susceptibility of several other Pinus spp. present in Europe. There is a need for research on the susceptibility to Atropellis spp. of those European Pinus spp.

Pest categorisation of Scirtothrips citri

Abstract 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 pests 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.

Pest categorisation of Ips typographus

Abstract The Panel on Plant Health performed a pest categorisation of the eight‐toothed spruce bark beetle, Ips typographus L. (Coleoptera: Curculionidae, Scolytinae), for the EU. I. typographus is a well‐defined and distinguishable species, recognised mainly as a pest of spruce (Picea spp.) in Eurasia. It also attacks other conifers such as Abies spp., Larix spp., Pinus spp. and Pseudotsuga menziesii. Native to Eurasia, I. typographus has spread from the native range of spruce to new areas in Eurasia where spruce has been planted, and is now widely distributed throughout the EU (22 Member states). It is a quarantine pest listed in Annex IIB of Council Directive 2000/29/EC for Ireland and United Kingdom as protected zones. Coniferous wood, bark and wood packaging material are considered as pathways for the pest, which is also able to disperse by flight over tens of kilometres. The insects normally establish on fallen trees but can also mass‐attack healthy trees, killing millions of spruces. The males produce pheromones that attract conspecifics of both sexes. Each male attracts one to four females; each female produces 2–80 offspring. The insects also inoculate pathogenic fungi to their hosts. There are one to three generations per year. The wide current geographic range of I. typographus suggests that it is able to establish anywhere in the EU where its hosts are present. Sanitary thinning or clear‐felling are the major control methods. Pheromone mass trapping is presently judged unreliable because of the large dispersal capacity of the pest. Quarantine measures are implemented to prevent entry in yet uncolonised areas. All criteria assessed by EFSA for consideration as potential protected zone quarantine pest are met. The criteria for considering I. typographus as a potential regulated non‐quarantine pest are not met since plants for planting are not a pathway.

Pest categorisation of Synchytrium endobioticum

Abstract The Panel on Plant Health performed a pest categorisation of the fungus Synchytrium endobioticum, the causal agent of potato wart disease, for the European Union (EU). The identity of the pest is well established and reliable methods exist for its detection and identification. S. endobioticum is present in most continents. The pest is listed in Annex IAII of Directive 2000/29/EC and is present with a restricted and fragmentary distribution in the EU. The major host is Solanum tuberosum (potato), but in Mexico, the pest also affects wild Solanum spp. S. endobioticum could potentially enter the EU through multiple pathways associated with soil as substrate for non‐host plants, contaminant or commodity. The presence of the pest in 16 EU Member States characterised by different climatic conditions suggests that it could establish in the rest of the EU. The disease induces the formation of warts on potato tubers, stolons and stem bases reducing plant growth and yield and making tubers unmarketable. Additional losses may occur during storage. The only available strategy to control the disease and prevent it from spreading is the application of strict phytosanitary measures and the cultivation of potato varieties resistant to the pathotype(s) present in the infested field(s). Specific phytosanitary measures exist (Council Directive 69/464/EEC) for the control of potato wart disease in the EU. The main uncertainties refer to the distribution and host range of the pest, and the importance of some pathways of entry. S. endobioticum meets all the criteria assessed by EFSA for consideration as potential Union quarantine pest. The criteria for considering S. endobioticum as a potential Union regulated non‐quarantine pest are not met since, in addition to potato seed tubers, soil (as commodity, substrate or contaminant) and ware potato tubers are major means of spread.

Guidance on quantitative pest risk assessment

Abstract This Guidance describes a two‐phase approach for a fit‐for‐purpose method for the assessment of plant pest risk in the territory of the EU. Phase one consists of pest categorisation to determine whether the pest has the characteristics of a quarantine pest or those of a regulated non‐quarantine pest for the area of the EU. Phase two consists of pest risk assessment, which may be requested by the risk managers following the pest categorisation results. This Guidance provides a template for pest categorisation and describes in detail the use of modelling and expert knowledge elicitation to conduct a pest risk assessment. The Guidance provides support and a framework for assessors to provide quantitative estimates, together with associated uncertainties, regarding the entry, establishment, spread and impact of plant pests in the EU. The Guidance allows the effectiveness of risk reducing options (RROs) to be quantitatively assessed as an integral part of the assessment framework. A list of RROs is provided. A two‐tiered approach is proposed for the use of expert knowledge elicitation and modelling. Depending on data and resources available and the needs of risk managers, pest entry, establishment, spread and impact steps may be assessed directly, using weight of evidence and quantitative expert judgement (first tier), or they may be elaborated in substeps using quantitative models (second tier). An example of an application of the first tier approach is provided. Guidance is provided on how to derive models of appropriate complexity to conduct a second tier assessment. Each assessment is operationalised using Monte Carlo simulations that can compare scenarios for relevant factors, e.g. with or without RROs. This document provides guidance on how to compare scenarios to draw conclusions on the magnitude of pest risks and the effectiveness of RROs and on how to communicate assessment results.

Evaluation of a paper by Guarnaccia et al. (2017) on the first report of Phyllosticta citricarpa in Europe

Abstract The Plant Health Panel reviewed the paper by Guarnaccia et al. (2017) and compared their findings with previous predictions on the establishment of Phyllosticta citricarpa. Four species of Phyllosticta were found by Guarnaccia et al. (2017) in Europe. P. citricarpa and P. capitalensis are well‐defined species, with P. citricarpa recorded for the first time in Europe, confirming predictions by Magarey et al. (2015) and EFSA (2008, 2014, 2016) that P. citricarpa can establish in some European citrus‐growing regions. Two new species P. paracitricarpa and P. paracapitalensis were also described, with P. paracitricarpa (found only in Greece) shown to be pathogenic on sweet orange fruits. Genotyping of the P. citricarpa isolates suggests at least two independent introductions, with the population in Portugal being different from that present in Malta and Italy. P. citricarpa and P. paracitricarpa were isolated only from leaf litter in backyards. However, since P. citricarpa does not infect or colonise dead leaves, the pathogen must have infected the above living leaves in citrus trees nearby. Guarnaccia et al. (2017) considered introduction to be a consequence of P. citricarpa having long been present or of illegal movement of planting material. In the Panels view, the fruit pathway would be an equally or more likely origin. The authors did not report how surveys for citrus black spot (CBS) disease were carried out, therefore their claim that there was no CBS disease even where the pathogen was present is not supported by the results presented. From previous simulations, the locations where Guarnaccia et al. (2017) found P. citricarpa or P. paracitricarpa were conducive for P. citricarpa establishment, with number of simulated infection events by pycnidiospores comparable to sites of CBS occurrence outside Europe. Preliminary surveys by National Plant Protection Organisations (NPPOs) have not confirmed so far the findings by Guarnaccia et al. (2017) but monitoring is still ongoing.