Sarah Green

Image of Sarah Green
Forest Pathologist and Programme Manager
Forest Research

Sarah obtained her PhD in plant pathology in 1995 from Lincoln University, New Zealand and subsequently worked as a plant pathologist in Canada. Since 2001 Sarah has been the senior forest pathologist leading the pathology group at Forest Research’s Northern Research Station, conducting research into a range of tree diseases and disorders including birch dieback, horse chestnut bleeding canker and drought stress. Currently she manages Forest Research’s Programme on Understanding Biotic Threats to Resilience and is the Principal Investigator on the interdisciplinary PHYTO-THREATS LWEC Phase 3 project which addresses global threats from Phytophthora species. Her main research interests are distribution, detection methods, biology and evolutionary genetics of forest pathogens, with a particular recent focus on emerging Phytophthora diseases.

Projects

Project Lead: Mariella Marzano
Three projects (PHC2019/04/05/06) were conducted in 2020/21 that investigated large-scale biosecurity risks to Scotland from several supply-chains and planting approaches. This project was commissioned, within the original scope of the aforementioned projects, to conduct further research with a strong likelihood of strengthening and expanding their findings. This project seeks to engage with hard-to-reach actors and the wider sector through their membership organisations.

PHC2021/08 will implement an Action Research approach, delivered through workshops co-designed with network organisations, to better understand current plant biosecurity risks in several sectors, to identify their plant health knowledge needs, and to begin to embed biosecurity training within existing organisations, programmes and processes.

The outcomes of the project will be:
• An enhanced understanding of the knowledge and training needs of different sectors and the identification of biosecurity actions that will fill some of the gaps identified by PHC2019/04/05/06
• The identification of further training needs and potential approaches to address the problems identified
• A legacy of close working relationships between the PHC and several network organisations, key to future plant biosecurity research or training delivery activities
Project Lead: Chris Pollard
Whilst it is generally agreed that ‘prevention is better than cure’ in plant health, translating such logic into precautionary actions does not always happen. Precautions can be encouraged in a variety of ways – through development of implementable actions, risk assessments, encouragement of best practice, and general appeals to adopt approaches which prevent future losses. However, this does not adequately address risky behaviour. Whilst better information may not be sufficient to change practices, there is a weakness in our ability to justify precaution. This project seeks to address this gap by considering whether there are different approaches, or additional information which might be considered.

Drawing upon and summarise existing literature, in addition to engagement with experts and practitioners with knowledge of existing sectoral practices in Scotland, UK and internationally, as well as gap analysis, the project will generate a better understanding of the rationale for taking precautions and an improved evidence base with which to justify taking action, answering four main questions:
• What are the current barriers to adopting precautionary measures?
• How can barriers be reduced?
• What are the limitations of the current risk assessment process?, and
• What are the priority areas for action and further research?
Project Lead: Matt Elliot
Plant health risks associated with poor composting practice or imported carrier products as peat alternatives are not well understood. Best practice guidance to minimise the plant health risks to Scotland from these activities is needed.

This work will examine and define the extent to which current UK and Scottish regulations and voluntary schemes control the way growing medium constituents must be treated prior to their inclusion in growing media, to generate an understanding around mitigating risks of spread of plant pathogens. Workshops with stakeholders will improve understanding of current practices and perceptions of alternative ‘best practice’ options for nurseries managing waste materials and for biosecurity risks of using reduced peat and peat-free growing media. A concurrent diagnostic study will identify Phytophthora species present in waste heaps from nurseries located in Scotland and the potential for these pathogens to spread into healthy plant stock either aerially or via water run-off and soil transfer.

Findings will be combined with a comprehensive desk-based study and feed into follow-up workshops on the development and introduction of ‘best practice’ guidance on the most appropriate and safest ways to manage waste growing media and plant material, to be built into the Plant Health Management Standard.
Project Lead: Mariella Marzano
The UK and Scotland have ambitious tree planting targets, with a major driver being carbon sequestration. Scotland’s Forest Strategy outlines a target of 15,000 ha per year. In addition to carbon management, other major drivers for tree planting are commercial forestry, habitat restoration and the establishment of new woodlands for biodiversity and amenity value. Scotland’s Forest Strategy outlines a target of 3,000-5,000 ha of new native woodland per year, and restoration of an additional 10,000 ha of native woodland. This involves planting a large volume of trees. There is considerable uncertainty as to where and how this volume of trees will be sourced, and associated uncertainty as to the biosecurity threats posed. The aim of this project is to improve our understanding of current biosecurity awareness and practices within the arenas of woodland creation/ expansion and habitat restoration in Scotland.

Impact: Determine the main barriers to ensuring that future planting for environmental restoration and conservation will minimise plant health risks.
Project Lead: Mariella Marzano
Large scale infra-structure projects such as transport networks and major housing projects typically include extensive landscaping and planting programmes. These operate at a large scale, often require instant visual impacts (semi-mature shrubs and trees) and face significant cost pressures. The modest scale of domestic production creates challenges in obtaining material from local sources, which can favour low-cost large-scale plant imports with associated risks of pest and disease entry. This project will fill in key knowledge gaps with those responsible for selecting, procuring and planting plants and trees on a large-scale to provide an understanding of how/whether biosecurity features in their decision-making and make recommendations for any changes required to improve bio-secure practices.

Impact: Provide Scottish Government policy with an assessment of the major biosecurity pitfalls and opportunities arising from large-scale landscaping plantings.
Project Lead: Mariella Marzano
Retail horticulture is a large-scale industry in the UK, with ornamental horticulture and landscaping worth an estimated £24.2 billion national GDP in 2017. The industry is characterised by a large volume of individual transactions and the transport of a diverse range of plant materials (with accompanying soil and packaging) to a highly distributed set of final destinations (households). These horticultural sales represent a complex and pervasive vector network, which carries the risk of transportation of pests and pathogens to surrounding parks and gardens, agricultural systems, woodlands, forests and the wider environment. The diversity of the plant material in trade and the multitude of suppliers and recipients creates a major challenge for managing biosecurity. This project will identify decision-makers, their knowledge, attitudes, and behaviours relating to plant health, and assess opportunities and barriers to better plant biosecurity and the potential role of a Plant Health Assurance Scheme.

Impact: This project will enable policy to identify and prioritise plant biosecurity vulnerabilities from non-specialist and online horticultural sales.
Project Lead: Carolyn Riddell
The oomycete Phytophthora ramorum has caused substantial losses of Scottish forests in recent years due to widespread mortality of European larch trees (Larix decidua). Since 2009, legislation and policies have been implemented to control P. ramorum outbreaks on larch including the use of a 250 m larch ‘fire-break’, although it is unclear whether this distance is optimal for disease control. A project funded by Scottish Forestry is using a P. ramorum-specific qPCR assay to compare several spore trapping techniques for quantifying wind- and rain-borne inoculum and to better estimate inoculum dispersal distance. This project adds value to that of the Scottish Forestry-commissioned work, through evaluation of metabarcoding as an alternative method to both monitor P. ramorum inoculum dispersal and detect a broader range of aerially dispersed Phytophthora species. A second objective is to determine the lineage composition of P. ramorum inoculum throughout the observed peak sporulation period.

Impact: Timely management and prioritisation of policy to manage P. ramorum and facilitate early forecasting of other Phytophthora outbreaks.
Project Lead: April Armstrong
The oomycete Phytophthora ramorum has caused substantial losses of Scottish forests in recent years due to widespread mortality of European larch trees (Larix decidua). Infected trees are subject to statutory felling notices in an effort to reduce sporulation potential. Nevertheless, there are concerns about the multiple pathways by which spores might be transferred to new sites. There have been assessments of soil moved by mountain biking and walking/running resulting in evidence to support the Forestry Commission’s Keep-it-Clean campaign. This study will assess soil/plant material collected from commercial harvesting equipment (tyres, treads, mud guards etc.). PHC support will enable a wider range of diagnostic tests to be carried out, testing the robustness of the methods and examining the potential for multiple Phytophthora species to be transferred.

Impact: Add to the evidence base underpinning public and sector-facing biosecurity campaigns and improve disease management and restrict spread of the disease.

Publications

The potential of ecological and epidemiological models to inform assessment and mitigation of biosecurity risks arising from large scale planting

October 2021

Large scale planting projects linked to infra-structure such as transport networks and major housing projects or to planting for environmental benefits (e.g., urban greening, woodland restoration) pose high biosecurity risks due to the high number and types of plants involved. This report focusses on whether and how ecological and epidemiological model frameworks can inform assessment and mitigation of biosecurity risks from large scale planting using a combination of literature review and stakeholder engagement.  The project aimed to identify priority steps to develop more useful models and tools for assessing biosecurity risks from planting in the future.

Forestry, Horticulture, Environment | Final Report and Policy Document

Metabarcoding analysis of Phytophthora diversity in spore traps and implications for disease forecasting in the P. ramorum management zone

May 2021

Surveillance and monitoring of airborne pathogens is a key tool in the management of healthy forests and controlling disease outbreaks. A Scottish Forestry-funded project was carried out in autumn 2019 to validate different spore-trapping techniques for monitoring airborne P. ramorum inoculum using a species-specific qPCR assay. This project aimed to add further value to the Scottish Forestry project by investigating the suitability of DNA metabarcoding for screening spore trap samples for P. ramorum and other Phytophthora species, seeking early data for aerially dispersed Phytophthora species that may become problematic in UK forests. The study highlighted the value of both monitoring P. ramorum dispersal and detecting other Phytophthora species, to predict and understand changes in disease severity in UK tree host species. Recommendations included that the use of both rain and wind-borne inoculum capture methods might be advantageous due to the variety of weather conditions under which inoculum can disperse.  Lineage testing in Southwest Scotland should be carried out to look at the prevalence of lineage EU1 in the EU2 area and to monitor for presence of North American lineages. Development of a new DNA barcode more specific to Phytophthora would be beneficial.