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Head of Tree Health Diagnostic and Advisory Service

To provide an effective, efficient and impartial disease diagnostic and advisory service on tree health.

Ana Pérez-Sierra joined the Forest Research in 2013. Since 1993 she has been working on the diagnosis of fungal plant diseases. From 1995 to 2003 she worked as a Plant Pathologist at the Royal Horticultural Society, Wisley Gardens, Surrey (UK).

From 2004 to 2013 she was the Coordinator of the Spanish Reference Laboratory for the Identification of Plant Pathogenic Fungi under the authority of Spanish Ministry of Agriculture, Food and Rural Environment. She obtained her PhD at Birkbeck, University of London, studying systematics, diagnostics and epidemiology of the fungal genus Armillaria.


  • Member of the Spanish Society for Plant Pathology
  • Member of the Spanish Arboricultural Association
  • Member of the American Phytopathological Society
Head of Tree Health Diagnostic and Advisory Service
Tree health

Forest Research

Alice Holt Lodge


Surrey GU10 4LH


Related Research


EUPHRESCO 2020-A-339- Seed-borne pathogens of conifers (Cosepath)

There is a need to raise awareness about the potential risks of introducing pests and diseases through seed movement and trade.

Status current


Focus on emerging Phytophthoras

Emerging diseases of forests caused by new and exotic Phytophthora species (POnTE project)

Status current
Focus on Hymenoscyphus fraxineus

Emerging diseases of forests caused by Hymenoscyphus fraxineus

Pest Organisms Threatening Europe (POnTE)

Collaborative European research action against emerging plant pathogens that threaten plant and trees in Europe.

Related Publications


First report of Phytophthora pluvialis in Europe causing resinous cankers on western hemlock

This is the first report of P. pluvialis in Europe. This is also the first published report of P. pluvialis causing resinous cankers on western hemlock worldwide.


Other Research

Peer reviewed journal articles

Pérez-Sierra A, Jung MH, Jung T. (2022). Survey and monitoring of Phytophthora species in natural ecosystems: Methods for sampling, isolation, purification, storage, and pathogenicity tests. In: Luchi, N. (eds) Plant Pathology. Methods in Molecular Biology, vol 2536. Humana, New York, NY.

Brunetti A, Heungens K, Hubert J, Ioos R, Bianchi GL, De Amicis F, Chandelier A, Van Der Linde S, Pérez-Sierra A, Gualandri V. et al. (2022). Interlaboratory performance of a real-time PCR method for detection of Ceratocystis platani, the agent of canker stain of Platanus spp. J. Fungi, 8, 778.

Mora-Sala B, León M, Pérez-Sierra A, Abad-Campos P. (2022). New reports of Phytophthora species in plant nurseries in Spain. Pathogens 2022, 11, 826.

Pérez-Sierra A, Jones B, Biddle M, Webber J. (2022). Phytophthora pluvialis- a new threat to forestry? Quarterly Journal of Forestry 116: 128-130.

Pérez-Sierra A. (2022). Together we can help to protect our trees. Trees (Spring issue Institute of Chartered Foresters): 14-15.

Pérez-Sierra A, Chitty R, Eacock A, Jones B, Biddle M, Crampton M, Lewis A, Olivieri L & Webber JF. (2022). First report of Phytophthora pluvialis in Europe causing resinous cankers on western hemlock. New Dis Rep, 45, 1–2.

Romon-Ochoa P, Kranjec Orlović J, Gorton C, Lewis A, van der Linde S, Pérez-Sierra A. (2022).  New detections of chestnut blight in Great Britain during 2019–2020 reveal high Cryphonectria parasitica diversity and limited spread of the disease. Plant Pathology

Green S, Cooke DEL, Dunn M, Barwell L, Purse B, Chapman DS, Valatin G, Schlenzig A, Barbrook J, Pettitt T, Price C, Pérez-Sierra A, Frederickson-Matika D, Pritchard L, Thorpe P, Cock PJA, Randall E, Keillor B, Marzano M. (2021). PHYTO-THREATS: Addressing threats to UK forests and woodlands from Phytophthora; Identifying risks of spread in trade and methods for mitigation. Forests. 2021; 12:1617.

Pérez-Sierra A, Hardy C, Chitty R, Lewis A, McCartan S. (2021). First report of Sirococcus piceicola associated with Sitka spruce seed in Britain. New Disease Reports, 44,1–2.

González M, Reynolds C, Forster J, van der Linde S, Parratt M, Dvorak M, Robertshaw B, Pérez-Sierra A. (2021). Incidence of the emerging pathogen Neonectria neomacrospora on Abies taxa in the National Arboreta in England (UK). Forest Ecology and Management 2021, 492.

Jung T, Horta Jung M, Webber JF, Kageyama K, Hieno A, Masuya H, Uematsu S, Pérez-Sierra A, Harris AR, Forster J, Rees H, Scanu B, Patra S, Kudláček T, Janoušek J, Corcobado T, Milenković I, Nagy Z, Csorba I, Bakonyi J, Brasier CM. (2021). The destructive tree pathogen Phytophthora ramorum originates from the Laurisilva forests of East Asia. Journal of Fungi. 2021; 7:226.

Van der Linde S, Pérez-Sierra A, Needham RS, Combes M, McCartan S (2021). Identification, detection and eradication of Hymenoscyphus fraxineus from ash (Fraxinus excelsior) seeds. Forestry 2021; 00, 1–12, https://doi:10.1093/forestry/cpab017

Landa BB, Arias-Giraldo LF, Henricot B, Montes-Borrego M, Shuttleworth LA, Pérez-Sierra, A. (2021). Diversity of Phytophthora species detected in disturbed and undisturbed British soils using high-throughput sequencing targeting ITS rRNA and COI mtDNA regions. Forests 2021, 12, 229.

Crow P, Perez-Sierra A, Kavčič A, Lewthwaite K, Kolšek M, Ogris N, Piškur B, Kus Veenvliet J, Zidar S, Sancisi-Frey S, de Groot M. (2020). Using Citizen Science to monitor the spread of tree pests and diseases: outcomes of two projects in Slovenia and the UK. Management of Biological Invasions 11(4): 703–719,

Barwell LJ, Pérez-Sierra A, Henricot B, Harris A, Burgess TI, Hardy G, Scott P, Williams N, Cooke D, Green S, Chapman DS, Purse BV. (2020). Evolutionary trait-based approaches for predicting global impacts of pathogens in the genus Phytophthora.  Journal of Applied Ecology

Jung T, Scanu B, Brasier CM, Webber J, Milenković I, Corcobado T, Tomšovský M, Pánek M, Bakonyi J, Maia C, Bačová A, Raco M, Rees H, Pérez-Sierra A, Horta Jung M. (2020). A Survey in natural forest ecosystems of Vietnam reveals high diversity of both new and described Phytophthora taxa including P. ramorum. Forests. 2020; 11:93.

Brown N, Pérez‑Sierra A, Crow P, Parnell S. (2020). The role of passive surveillance and citizen science in plant health. CABI Agriculture and Bioscience 1: 17

Blake M, Pérez-Sierra A. (2020). Pests and diseases of conifers what do we know about green spruce aphid (Elatobium abietinum) and Swiss needle cast (Nothophaeocryptopus gaeumannii)? Quarterly Journal of Forestry 114 (2): 93-97.

Pérez-Sierra A, van der Linde S, Romón-Ochoa P, Jones B, Gorton C. (2020). First report of Cryphonectria parasitica on abandoned galls of Dryocosmus kuriphilus on sweet chestnut in the United Kingdom. New Disease Reports 41, 34. []

Shuttleworth L, Lewis A, Gorton C, Pérez-Sierra A. (2020). Dendrostoma luteum Persoonia – Fungal Planet Description Sheets. Persoonia 44: 382-383.

Pérez-Sierra A, Blake M, Gorton C, Lewis A, Chitty R, van der Linde S, Kendal T, Turner L, Armstrong A, Hendry S. (2019). The Tree Health Diagnostic and Advisory Service at Forest Research: reviewing the past six years. Arb Magazine 186, 41-45.

Pérez -Sierra A, Stewart A, Sancisi-Frey S, Plummer S, Pollard C, Clover G (2019). BRIGIT – A consortium for enhancing UK surveillance and response to Xylella fastidiosa. Quarterly Journal of Forestry 113, 166-168.

Romon-Ochoa P, Gorton C, Lewis A, van der Linde S, Webber J, Pérez-Sierra A. (2019). Hypovirulent effect of the Cryphonectria hypovirus 1 in British isolates of Cryphonectria parasitica Pest Management Science

González M, Pérez-Sierra A, Sánchez ME. (2019). Phytophthora oleae, a new root pathogen of wild olives.  Plant Pathology 68: 901-907.

Pérez-Sierra A, Romón-Ochoa P, Gorton C, Lewis A, Rees H, Van Der Linde S, Webber J. (2019). Population diversity of Cryphonectria parasitica infecting sweet chestnut (Castanea sativa) in Britain indicates multiple pathogen introductions. Plant Pathology 68, 727-737.

McMinn J, Perez-Sierra A. (2018). Neonectria neomacrospora on Abies spp. in Wales. Quarterly Journal of Forestry 112 (2): 111-116.

Jung T, Pérez–Sierra A, Durán A, Horta Jung M, Balci Y, Scanu B. (2018). Canker and decline diseases caused by soil- and airborne Phytophthora species in natural and semi–natural ecosystems. Persoonia 40: 182-220.

Rodriguez-Padron C, Siverio F, Perez-Sierra A, Rodriguez A. (2018). Isolation and pathogenicity of Phytophthora species and Phytopythium vexans recovered from avocado orchards in the Canary Islands, including Phytophthora niederhauserii as a new pathogen of avocado. Phytopathologia Mediterranea: 57, 183-200.

Perez-Sierra A, (2017). Update on Tree Health. CJS Focus on Forestry and Arboriculture. Published:  20 November 2017, in association with: Ancient Tree Forum.

Perez-Sierra A, Webber J, Birchal E, Carson-Taylor L, 2017. Things you need to know about Xylella fastidiosa. Forestry & Timber News, December 2017: 42-43.

Drakulic J, Gorton C, Pérez-Sierra A, Clover G, Beal L. Associations between Armillaria species and host plants in U.K. gardens. Plant Disease. Posted online on 11 Sep 2017.

Jung T, Scanu B, Bakonyi J, Seress D, Kovács GM, Durán A, Sanfuentes von Stowasser E, Schena L, Mosca S, Thu PQ, Nguyen CM, Fajardo S, González M, Pérez-Sierra A, Rees H, Cravador A, Maia C, Horta-Jung M. 2017. Nothophytophthora gen. nov., a new sister genus of Phytophthora from natural and semi-natural ecosystems. Persoonia 39: 143 –174.

Lewis A, Gorton C, Rees H, Webber J, Pérez-Sierra A, 2017. First report of Gnomoniopsis smithogilvyi causing lesions and cankers of sweet chestnut in the United Kingdom. New Disease Reports 35, 20.

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 (In Press)

González M., Pérez-Sierra A., Serrano M.S., Sánchez M.E. 2017. Two Phytophthora species causing decline of wild olive (Olea europaea subsp. europaea var. sylvestris). Plant Pathology. DOI: 10.1111/ppa.12649

Catalá S., Berbegal M., Pérez-Sierra A., Abad-Campos P. 2017. Metabarcoding and development of new real-time specific assays reveal Phytophthora species diversity in holm oak forests in eastern Spain. Plant Pathology 66: 115-123. DOI: 10.1111/ppa.12541

Jung T., Chang T.T., Bakonyi J., Seress D., Pérez-Sierra A., Yang X., Hong C., Scanu B., Fu C.H., Hsueh K.L., Maia C., Abad-Campos P., Léon M., Horta Jung M. 2017. Diversity of Phytophthora species in natural ecosystems of Taiwan and association with disease symptoms. Plant Pathology 66: 194-211. DOI: 10.1111/ppa.12564

Schlenzig A., Purser E., Perez-Sierra A. 2016. First finding of Phytophthora foliorum in the United Kingdom. New Disease Reports 34, 2.

Jung T., Orlikowski L., Henricot B., Abad-Campos P., Aday A. G., Aguín- Casal O., Bakonyi J., Cacciola S.O., Cech T., Chavarriaga D., Corcobado T., Cravador A., Decourcelle T., Denton G., Diamandis S., Doğmuş-Lehtijärvi H. T., Franceschini A., Ginetti B., Glavendekić M., Hantula J., Hartmann G., Herrero M., Ivic D., Horta Jung M., Lilja A., Keca N., Kramarets V., Lyubenova A., Machado H., Magnano di San Lio G., Mansilla Vázquez P. J., Marçais B., Matsiakh I., Milenkovic I., Moricca S., Nagy Z. Á., Nechwatal J., Olsson C., Oszako T., Pane A., Paplomatas E. J., Pintos Varela C., Prospero S., Rial Martínez C., Rigling D., Robin C., Rytkönen A., Sánchez M. E., Scanu B., Schlenzig A., Schumacher J., Slavov S., Solla A., Sousa E., Stenlid J., Talgø V., Tomic Z., Tsopelas P., Vannini A., Vettraino A. M., Wenneker M., Woodward S. and Peréz-Sierra A. 2016. Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseases. Forest Pathology 46: 134-163. DOI: 10.1111/efp.12239

Tubby K.V., Pérez-Sierra A. 2015. Pests and pathogen threats to plane (Platanus) in Britain, Arboricultural Journal, 37 (2): 85-98. DOI: 10.1080/03071375.2015.1066558

Pérez-Sierra A., Gorton C., Lewis A., Kalantarzadeh M., Sancisi-Frey S., Brown A.V., Hendry S. 2015. First report of shoot blight caused by Sirococcus tsugae on Atlantic cedar (Cedrus atlantica) in Britain.

Perez-Sierra A, Kalantarzadeh M, Sancisi-Frey S, Brasier CM, 2015. Phytophthora siskiyouensis causing stem lesions and cankers on Alnus incana. New Disease Reports 31, 17.

Català, S., Pérez-Sierra, A., Abad-Campos, P. (2015). The use of genus-specific amplicon pyrosequencing to assess Phytophthora species diversity using eDNA from soil and water in northern Spain. PLoS ONE 10(3): e0119311. DOI:10.1371/journal.pone.0119311.

Berbegal M., Landeras E., Sanchez D., Abad-Campos P., Perez-Sierra A., Armengol J. 2015. Evaluation of Pinus radiata seed treatments to control Fusarium circinatum: effects on seed emergence and disease incidence. Forest Pathology DOI: 10.1111/efp.12204

Redondo M.A., Perez-Sierra A., Abad-Campos P., Torres L., Solla A., Reig-Armiñana J., Garcia-Breijo F. 2015. Histology of Quercus ilex roots during infection by Phytophthora cinnamomi. Trees DOI 10.1007/s00468-015-1275-3

Scanu B., Linaldeddu B.T., Perez-Sierra A., Deidda A., Franceschini A. (2014). Phytophthora ilicis as a leaf and stem pathogen of Ilex aquifolium in Mediterranean islands. Phytopathologia Mediterranea 53 (3): 480−490.

Henricot B., Pérez Sierra A. and Jung T. (2014). Phytophthora pachypleura sp. nov., a new species causing root rot of Aucuba japonica and other ornamentals in the United Kingdom. Plant Pathology DOI: 10.1111/ppa.12194.

Berbegal M., López-Cortés I., Salazar D., Gramaje D., Pérez Sierra A., García-JiméneJ Z., and Armengol, J. (2014). First report of Alternaria black spot of pomegranate caused by Alternaria alternata in Spain. Plant Disease 98 (5), 689.

Abad Z.G., Abad J.A., Cacciola S.O., Pane A., Faedda R., Moralejo E., Pérez-Sierra A., Abad-Campos P., Alvarez-Bernaola L.A., Bakonyi J., Józsa A., Herrero M.A., Burgess T.I., Cunnington J.H., Smith I.W., Balci Y., Blomquist C., Henricot B., Denton G., Spies C., Mcleod A., Belbahri L., Cooke D., Kageyama K., Uematsu S., Kurbetli I. and Degirmenci K. 2014. Phytophthora niederhauserii sp. nov., a polyphagous species associated with ornamentals, fruit trees and native plants in 13 countries. Mycologia, 106 (3): 431-447. DOI: 10.3852/12-119

Gramaje D., León M., Pérez-Sierra A., Burgess T. and Armengol J. (2014). New Phaeoacremonium species isolated from sandalwood trees in Western Australia. IMA Fungus 5 (1), 67–77.

Pérez Sierra A., López-García C., León M., García-Jiménez J., Abad-Campos P. and Jung T. (2013). Previously unrecorded low temperature Phytophthora species associated with Quercus decline in a Mediterranean forest in Eastern Spain. Forest Pathology 43 (4), 331-339.

Pérez Sierra, A. and Jung T. (2013). Phytophthora in woody ornamental nurseries. In: Phytophthora a global perspective. CABI (ISBN 9781780640938) pp. 166- 177.

Berbegal, M., Pérez-Sierra, A., Armengol, J. and Grünwald, N.J. (2013). Evidence for multiple introductions and clonality in Spanish populations of Fusarium circinatum. Phytopathology 103 (8), 851-861.

Pérez Sierra, A., Mora-Sala, B., León, M., García-Jiménez, J. and Abad-Campos, P. (2012). Enfermedades causadas por Phytophthora en viveros de plantas ornamentales. Boletín Sanidad Vegetal Plagas 1, 143 – 156.

Agustí Brisach, C., Pérez-Sierra, A., Armengol, J., García-Jiménez, J. and Berbegal M. (2012). Efficacy of hot water treatment to reduce the incidence of Fusarium circinatum on Pinus radiata seeds. Forestry 85 (5), 629-635.

Berbegal, M., Pérez-Sierra, A. and Armengol, J. (2012). First Report of Sirosporium celtidis causing a foliar disease of European Hackberry in Spain. Plant Disease 96, 1826.

Gramaje, D., Agustí-Brisach, C., Pérez-Sierra, A., Moralejo, E., Olmo, D., Mostert, L., Damm, U. and Armengol, J. (2012). Fungal trunk pathogens associated with wood decay of almond trees in Mallorca (Spain). Persoonia 28, 1-13.

Agustí Brisach, C., Pérez-Sierra, A., García-Figueres, F., Montón, C. and Armengol, J. (2011). First report of damping-off caused by Cylindrocarpon pauciseptatum on Pinus radiata in Spain. Plant Disease 95, 874.

Pérez Sierra, A. Álvarez, L.A., Vercauteren, A., Heungens K. and Abad-Campos, P. (2011). Genetic diversity, sensitivity to phenylamide fungicides and aggressiveness of Phytophthora ramorum on CamelliaRhododendron and Viburnum plants in Spain. Plant Pathology 60 (6), 1069–1076.

Pérez Sierra, A., León, M., Álvarez, L.A., Alaniz, S., Berbegal, M., García-Jiménez, J. and Abad-Campos, P. (2010). Outbreak of a new Phytophthora sp. associated with severe decline of almond trees in Eastern Spain. Plant Disease 94, 534-541.

Corcobado, T., Cubera, E., Pérez-Sierra, A., Jung, T. and Solla, A. (2010). First report of Phytophthora gonapodyides involved in the decline of Quercus ilex in xeric conditions in Spain. Plant Pathology 22, 33.

Solla, A., Pérez-Sierra, A., Corcobado, T., Haque, MM., Diez, J.J. and Jung, T. (2010). Phytophthora alni on Alnus glutinosa reported for the first time in Spain. Plant Pathology 59 (4), 798.

Hernández-Hernández, J., Espino, A., Rodríguez-Rodríguez, J.M., Pérez-Sierra, A., León, M., Abad-Campos, P. and Armengol, J. (2010). Survey of diseases caused by Fusarium spp. on palm trees in the Canary Islands. Phytopatologia Mediterreanea 49, 84-88.

Moralejo, A., Pérez-Sierra, A., Álvarez, L.A., Belbahri, L., Lefort, F. and Descals E. (2009). Multiple alien Phytophthora taxa discovered on diseased ornamental plants in Spain. Plant Pathology 58, 100-110.

Armengol, J., Gramaje, D., Pérez-Sierra, A., Landeras, E., Alzaguray, R., Martos, S. and Luque, J. (2008). First report of canker disease caused by Neofusicoccum australe on eucalyptus and pistachio in Spain. Plant Disease 92, 980.

Gramaje, D., Alaniz, S., Pérez-Sierra, A., Abad-Campos, P., García-Jiménez, J. and Armengol, J. (2008). First report of Phaeoacremonium scolyti causing Petri disease of grapevine in Spain. Plant Disease 92, 836.

Pérez Sierra, A., Landeras, E., León, M., Berbegal, M., Armengol,J. and García-Jiménez, J. (2007). Characterization of Fusarium circinatum from Pinus spp. in Northern Spain. Mycological Research 111, 832 – 839.

Álvarez, L.A., Pérez-Sierra, A. and García-Jiménez, J. (2007). Bleeding canker on Mesquite in Peru caused by Phytophthora syringae. Plant Disease 91, 226.

Álvarez, L.A., Pérez-Sierra, A., Armengol, J. and García-Jiménez, J. (2007). Characterization of Phytophthora nicotianae isolates causing collar and root rot of common lavender and rosemary plants in Spain. Journal of Plant Pathology 89, 251 – 254.

Gramaje, D., Alaniz, S., Pérez-Sierra, A., Abad-Campos, P., García-Jiménez, J. and Armengol, J. (2007). First report of Phaeoacremonium mortoniae causing Petri disease of grapevine in Spain. Plant Disease 91, 1296.

Álvarez, L.A., Pérez-Sierra, A., Landeras, E., García-Jiménez, J. and Abad-Campos, P. (2007). First report of leaf spot and twig blight of Rhododendron spp. caused by Phytophthora hibernalis in Spain. Plant Disease 91, 909.

Pérez Sierra, A., Álvarez, L.A., León, M., Abad-Campos, P., Armengol, J. and García-Jiménez, J. (2007). First report of leaf spot, blight and stem lesions caused by Cylindrocladium pauciramosum on Callistemon in Spain. Plant Disease 91, 1057.

Pérez Sierra, A., Álvarez, L.A., Henricot, B., García-Jiménez, J. and Armengol, J. (2006). Cylindrocladium pauciramosum causes root and collar rot of Polygala myrtifolia in Spain. Plant Pathology 55, 298.

Álvarez, L.A., Pérez-Sierra, A., León, M., Armengol, J., García-Jiménez, J. (2006). Lavander cotton (Santolina chamaecyparissus) root rot: A new host of Phytophthora tentaculata detected in Spain. Plant Disease 90, 523.

Álvarez, L.A., Armengol, J., Pérez-Sierra, A., León, M., Abad-Campos, P., Vicent, A. and García-Jiménez, J. (2005). First report of Phoma exigua var. heteromorpha causing oleander dieback in Spain. Plant Disease 89, 775.

Landeras, E., García, P., Fernández, Y., Braña, M., Fernández-Alonso, O., Pérez-Sierra A., León, M., Méndez-Lodos, S., Abad-Campos, P., Berbegal, M., Beltrán, C., García-Jiménez, J. and Armengol, J., (2005). Outbreak of pitch canker caused by Fusarium circinatum on Pinus spp. in Northern Spain. Plant Disease 89, 1015.

Pérez Sierra, A. and Gorton, C. (2005). Survival of honey fungus in wood and bark chip mulches. The Plantsman 4, 204-207.

Pérez Sierra, A., Guillaumin, J-J., Spooner, B. and Bridge, P. (2004). Characterization of Armillaria heimii from Africa. Plant Pathology 53, 220-230.

Henricot, B., Waghorn, I., Denton, G., Pérez-Sierra, A. (2004). First report of fruit rot caused by Phytophthora syringae on Pyracantha in the UK. Plant Pathology 53, 805.