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Responsible for management of the Forest Research Northern Research Station’s (NRS) pathology laboratory, and for developing and carrying out research projects to address important tree health problems in UK forests, focusing on oomycete, fungal and bacterial diseases.

Leads the Coordination Team for the UK Strategic Priorities Fund Bacterial Plant Diseases Programme

Coordinates an international Euphresco project on early detection of Phytophthoras in nurseries and traded plants in EU and third countries.

Sarah Green joined Forest Research in 2001. She obtained a BSc (Hons) from the University of North Wales, Bangor, in 1990, and was awarded a Commonwealth Scholarship to undertake her PhD studies in plant pathology at Lincoln University, New Zealand, from 1991 to1995. Sarah then worked on the use of fungal pathogens as biocontrol agents based in Nova Scotia and Saskatchewan, Canada from 1995-2001, latterly as part of the Canadian Government Visiting Fellowship Scheme.

Current Projects
  • Coordination of science, stakeholder engagement and impact activities across nine funded UK projects aimed at understanding and countering bacterial plant diseases.
  • Early detection of Phytophthoras in nurseries and traded plants in EU and third countries.  This project is an international collaboration involving ten partner countries. The project aims to develop a co-ordinated strategy for the early detection of Phytophthora pathogens in plant nurseries and traded plants for planting across EU and third countries in order to inform best practice, complement phytosanitary regulation and to enhance engagement on Plant Health with traders operating in different countries.
  • Molecular detection of Phytophthoras in forest, woodland and urban garden environments: This research uses Illumina metabarcoding to examine the diversity of Phytophthora species in soil, water and aerial spore traps.
  • Evidence for natural resistance in Japanese larch to Phytophthora ramorum and in juniper to Phytophthora austrocedri.
Previous Research Projects
  • Principal Investigator on PHYTO-THREATS project: ‘Global threats from Phytophthora spp.; understanding drivers of emergence and opportunities for mitigation through nursery best practice’. This is a three-year collaborative research project funded by the Living With Environmental Change (LWEC) programme and part of the Tree Health and Plant Biosecurity Initiative.
  • Established and led the FR Research Programme ‘Understanding Biotic Threats’ 2015-2020 This programme aimed to increase our understanding of forest resilience to pests and pathogens and to mitigate risk of future outbreaks by i) investigating how environmental factors influence pest and pathogen behaviour, ii) examining the evidence for natural resistance in UK tree populations, iii) identifying key future threats and promoting preparedness for them and iv) investigating methods for improved surveillance and detection.
  • Investigating the biology of the causal agent of horse chestnut bleeding canker, Pseudomonas syringae pathovar aesculi.
  • Pathology of birch in Scotland (Dieback of birch)


  • Member of British Society for Plant Pathology
  • Editor for Plant Pathology
  • Senior Editor for the Journal of Plant Pathology
  • Received various travel awards from the British Society for Plant Pathology, including a Senior Fellowship for a study visit to the Norwegian Forest and Landscape Institute in 2008.
Forest Pathologist
Tree health

Forest Research

Northern Research Station


Midlothian EH25 9SY


Related Research


Molecular detection of Phytophthoras in forest, woodland and urban garden environments

A project entitled 'molecular detection of Phytophthoras in forest, woodland and urban garden environments' aims to; i) examine Phytophthora diversity in soil at forest, woodland and public garden sites in Scotland, ii) assess the feasibility of using Illumina metabarcoding technology combined with spore trapping for longer-term monitoring of aerial Phytophthora diseases, such as P. ramorum, and iii) to provide evidence to inform biosecurity and remediation policy aimed at limiting the introduction, spread and impact of Phytophthora diseases.

Status current
Understanding the threat posed by Phytophthora austrocedri to juniper in Britain

Phytophthora austrocedri is causing widespread mortality of native juniper in northern Britain. This project aims to provide the evidence base to guide juniper conservation strategies that mitigate the effects of the pathogen.

Global threats from Phytophthora spp. (PHYTO-THREATS)

The PHYTO-THREATS project aims to address the risks to UK forest and woodland ecosystems from Phytophthora by examining the distribution and diversity of Phytophthoras in UK plant nursery systems.

Using molecular technology to characterise the biology of Pseudomonas syringae pv. aesculi, causing bleeding canker of horse chestnut

Investigating the processes of infection of Pae on the woody parts of horse chestnut, the potential for its survival and dissemination in soil, water and other environmental substrates, its geographical origin of Pae and its pathways of spread in Europe and the biological function of Pae-specific genes which are implicated in virulence on a tree host

Drought stress in Sitka spruce in eastern Scotland and its association with a species of Phomopsis

Assessment and study of the extensive damage was reported on pole stage and older Sitka spruce along the Dee valley in north-east Scotland

Dieback of birch

Investigating the role of shoot fungi as agents of crown dieback of birch

Related Publications


Metabarcoding reveals a high diversity of woody host-associated Phytophthora spp. in soils at public gardens and amenity woodlands in Britain

A study of Phytophthora diversity in public gardens and amenity woodlands through the use of metabarcoding of soil samples.

Horse chestnut bleeding canker

Horse chestnut is an important amenity tree species which has been significantly affected over the past decade by a widespread outbreak of bleeding canker disease. Symptoms include rust-coloured or blackened bleeding cankers on the stem and branches, which can lead to tree mortality. The causal agent of this disease is the pathogenic bacterium Pseudomonas syringae […]

Potential impacts of drought and disease on forestry in Scotland

This study identified 288 medium or high drought risk forest sites in eastern Scotland, 125 of which include Sitka spruce as a major component. Sitka spruce is intolerant of drought and is known to have previously experienced drought damage such as tree mortality and stem cracking in eastern Scotland. Cases of direct drought damage, together […]

[Archive] Birch dieback in Scotland

A study was initiated in 2002 to examine the fungal pathology of birch dieback in Scotland. The main objectives of this project are to investigate the fungi infecting birch shoots in Scotland, identify the primary pathogens with the ability to infect healthy trees, determine the impact of these fungi on the national woodland resource, and […]

Peer reviewed journal articles

Donald, F., Hedges, C., Purse, B.V., Cunniffe, N.J., Green, S., Asaaga, F.A. 2024. Utility of decision tools for assessing plant health risks from management strategies in natural environments. Ecology and Evolution, 2024;14:e11308.

Schiffer-Forsyth, K., Frederickson Matika, D, Hedley, P.E., Cock, P.J.A., Green, S. 2023. Phytophthora in horticultural nursery green waste – a risk to plant health. Horticulturae 9, 616.

Dun, H.F., Hang Hung, T., Green, S., MacKay, J.J. 2022. Comparative transcriptomic responses of European and Japanese larches to infection by Phytophthora ramorum. BMC Plant Biology 22, 480 (2022)

Dun, H.F., Clarke, T-K., MacKay, J.J., Green, S. 2022. Exploring variation in susceptibility to Phytophthora ramorum in Japanese larch (Larix kaempferi). Forest Pathology

Valatin, G, Price, C., Green, S. 2022. Reducing disease risks to British forests: an exploration of costs and benefits of nursery best practice. Forestry 2022, 1-15.

Marzano, M., Dunn, M., Green, S. 2021. Perceptions of biosecurity-based accreditation in the plant trade: a UK example. Forests 12, 1741;

Green, S., Cooke, D.E.L., Dunn, M., Barwell, L., Purse, B. et al. 2021. PHYTO-THREATS: Addressing Threats to UK Forests and Woodlands from Phytophthora; Identifying Risks of Spread in Trade and Methods for Mitigation. Forests 12, 1617;

Donald, F., Purse, B.V., Green, S. 2021. Investigating the role of restoration plantings in introducing disease – a case study using Phytophthora. Forests 12 (6), 764;

Barwell, L., Perez-Sierra, A., Henricot, B., Harris, A., Burgess, T., Hardy, G., Scott, P., Williams, N., Cooke, D., Green, S., Chapman, D., Purse, B. 2020. Evolutionary trait-based approaches for predicting future global impacts of plant pathogens in the genus Phytophthora. Journal of Applied Ecology 00, 113.

Green, S., James, E.R., Clark, D., Clarke, T-K., Riddell, C.E. 2020. Evidence for natural resistance in Juniperus communis to Phytophthora austrocedri. Journal of Plant Pathology 103, 55-59.

Donald, F., Green, S., Searle, K., Cunniffe, N.K., Purse, B. 2020. Small scale variability in soil moisture drives infection of vulnerable juniper populations by invasive forest pathogen. Forest Ecology and Management 473, 118324.

Riddell, C.D., Dun, H.F., Elliot, M., Armstrong, A.C., Clark, M., Forster, J., Hedley, P.E., Green, S. 2020. Detection and spread of Phytophthora austrocedri within infected Juniperus communis woodland and diversity of co-associated Phytophthoras as revealed by metabarcoding. Forest Pathology.

Green, S., Riddell, C.E., Frederickson-Matika, D., Armstrong, A.C., Elliott, M., Forster, J., Hedley, P.E., Morris, J., Thorpe, P., Cooke, D.E.L., Sharp, P.M., Pritchard, L. 2020. Diversity of woody host-infecting Phytophthora species in public parks and botanic gardens as revealed by metabarcoding, and opportunities for mitigation through best practice. Sibbaldia 18, 67-82.

Riddell, C.E., Frederickson-Matika, D., Armstrong, A.C., Elliot, M., Forster, J., Hedley, P.E.,   Morris, J., Thorpe, P., Cooke, D.E.L., Pritchard, P., Sharp, P.M., & Green, S. (2019). Metabarcoding reveals a high diversity of woody host-associated Phytophthora spp. in soils at public gardens and amenity woodlands in Britain.

Henricot, B., Pérez-Sierra, A., Armstrong, A., Sharp, P. M., Green, S. 2017. Morphological and genetic analyses of the invasive forest pathogen Phytophthora austrocedri reveal two clonal lineages colonised Britain and Argentina from a common ancestral population. Phytopathology 107, 1532-1540.

Vettraino AM, Brasier CM, Webber JF, Hansen EM, Green S, Robin C, Tomassini A, Bruni N, Vannini A. 2017. Contrasting microsatellite diversity in the evolutionary lineages of Phytophthora lateralis. Fungal Biology 121 (2), 112-126.

Green, S., MacAskill, G.A., Dun, H., Armstrong, A.C., Henricot, B. 2016. First report of Phytophthora austrocedri infecting Nootka cypress in Britain New Disease Reports (2016) 33, 21.

Nowell, R.W., Sharp, P.M., Laue, B.E., Green, S. 2016. Comparative genomics reveals genes significantly associated with woody hosts in the plant pathogen Pseudomonas syringae. Molecular Plant Pathology 17, 1409-1424.

Elliot, M., Schlenzig, A.,Harris, C.M., Meagher, T.R., Green, S. (2015). An improved method for the qPCR detection of three Phytophthora spp. in forest and woodland soils in northern Britain. Forest Pathology 45, 537-539.

Green, S., Elliot, M., Armstrong, A., Hendry, S.J. (2015). Phytophthora austrocedrae emerges as a serious threat to juniper (Juniperus communis) in Britain. Plant Pathology 64, 456-466.

Mulholland, V., Elliot, M., Green¸ S. (2015). Diagnostics of tree diseases caused by Phytophthora species. Pp 59-74 In: Plant Pathology Techniques and Protocols, Second Edition. C. Lacomme (ed). Methods in Molecular Biology. Humana Press.

Laue, B.E., Steele, H., Green, S. (2014). Survival, cold tolerance and seasonality of infection of European horse chestnut (Aesculus hippocastanum) by Pseudomonas syringae pv. aesculi. Plant Pathology 63, 1417-1425.

Nowell, R.W., Green, S., Laue, B.E., Sharp, P.M. (2014). The extent of genome flux and its role in the differentiation of bacterial lineages. Genome Biology and Evolution 6, 1514-1529.

Reignoux, S., Green, S., Ennos, R. (2014). Molecular identification and relative abundance of cryptic Lophodermium species in natural populations of Scots pine, Pinus sylvestris L. Fungal Biology 118, 835-845.

Green, S., Laue, B.E., Steele, H., Nowell, R.W. (2014). Horse Chestnut Bleeding Canker. Forestry Commission Research Note 17(PDF-773K)

Mulholland, V., Schlenzig, A., MacAskill, G.A., Green, S. (2013). Development of a quantitative real-time PCR assay for the detection of Phytophthora austrocedrae, an emerging pathogen in Britain. Forest Pathology 43, 513-517.

Green, S., Laue, B.E., Nowell, R., Steele, H. (2013). Horse chestnut bleeding canker – a 21st Century tree pathogen. Pp 783-794 In: T. Fenning (ed.), Challenges and Opportunities for the World’s Forests in the 21st Century, Forestry Sciences 81.

Brasier, C.M., Franceschini, S, Vettraino, A.M., Hansen, E.M., Green, S., Robin, C., Webber, J.F., Vannini, A. (2012). Four phenotypically distinct lineages in Phytophthora lateralis. Fungal Biology 116, 1232-1249.

Green, S., Hendry, S.J., MacAskill, G.A., Laue, B.E. and Steele, H. (2012). Dieback and mortality of Juniperus communis in Britain associated with Phytophthora austrocedrae. New Disease Reports 26, 2.

Green, S., Brasier, C.M., Schlenzig, A., McCracken, A., MacAskill, G.A., Wilson, M. and Webber, J.F. (2012). The destructive invasive pathogen Phytophthora lateralis found on Chamaecyparis lawsoniana across the UK(PDF-981K) Forest Pathology 43, 19-28.

Green, S. and Webber, J.F. (2012). The emerging threat from Phytophthora to trees in Scotland. Scottish Forestry 66, 9-16.

Mulholland, V., MacAskill, G.A., Laue, B.E., Steele, H., Kenyon, D. and Green, S. (2012). Development and verification of a diagnostic assay based on EF1-alpha for the identification of Armillaria species in Northern Europe. Forest Pathology 42, 229-238.

Steele, H., Laue, B.E., MacAskill, G.A., Hendry, S.J. & Green, S. (2010). Analysis of the natural infection of European horse chestnut (Aesculus hippocastanum) by Pseudomonas syringae pv. aesculi. Plant Pathology 59 (6), 1005-1013.

Green, S., Studholme, D.J., Laue, B.E., Dorati, F., Lovell, H., Arnold, D., Cottrell, J.E., Bridgett, S., Blaxter, M., Huitema, E., Thwaites, R., Sharp, P.M., Jackson, R.W. and Kamoun, S. (2010). Comparative genome analysis provides insights into the evolution and adaptation of Pseudomonas syringae pv. aesculi on European horse chestnut. PLoS ONE 5(4): e10224.

De Silva, H., Castlebury, L.A., Green, S. and Stone, J.K. (2009). Characterisation and phylogenetic relationships of Anisogramma virgultorum and A. anomala in the Diaporthales (Ascomycota). Mycological Research 113: 73-81.

Green, S., Laue, B., Fossdal, C.G., A’Hara, S. and Cottrell, J. (2009). Infection of horse chestnut (Aesculus hippocastanum) by Pseudomonas syringae pv. aesculi and its detection by quantitative real-time PCR. Plant Pathology 58, 731-744

Green, S. and Ray, D. (2009). Climate change: risks to forestry in Scotland due to drought and fungal disease. Forestry Commission Research Note 8. Edinburgh, Scotland.

De Silva, H, Green, S., Woodward, S. (2008). Incidence and biology of Anisogramma virgultorum on birch in Scotland. Scottish Forestry 62 (4), 22-28.

DeSilva, H., Green, S. and Woodward, S. (2008). Incidence and severity of dieback in birch plantings associated with Anisogramma virgultorum and Marssonina betulae in Scotland. Plant Pathology 57 (2): 272-279.

Green, S., Hendry, S.J. and Redfern, D.B. (2008). Drought damage to pole-stage Sitka spruce and other species in north east Scotland. Scottish Forestry 62 (3): 10-18.

Green, S. and Castlebury, L. A. (2007). Connection of Gnomonia intermedia to Discula betulina and its relationship to other taxa in the Gnomoniaceae. Mycological Research 111:62-69.

Green, S. and MacAskill, G. A. (2007). Pathogenicity of Marssonina betulae and other fungi on birch. Plant Pathology 56, 242-250.

Green, S. (2005). First report of Septoria betulae causing leaf spot of birch in the United Kingdom. Plant pathology 54 (4): 580.

Brown, A., Green, S. and Hendry, S. (2005). Needle diseases of pine. Forestry Commission Information Note 67. Edinburgh, Scotland.

Green, S. (2005). Birch die-back in Scotland(PDF-721K). Forestry Commission Information Note 72. Edinburgh, Scotland.

Green, S. (2004). Fungi associated with shoots of silver birch (Betula pendula) in Scotland. Mycological Research 108 (11): 1327-1336.

Green, S., Peng, G., Connolly, T. and Boyetchko, S. M. (2004). Effect of moisture and temperature on disease of green foxtail caused by Drechslera gigantea and Pyricularia setariae. Plant Disease 88 (6): 605-612.

Green, S. (2003). A review of the potential for the use of bioherbicides to control forest weeds in the UK. Forestry 76 (3): 285-298.