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Phytophthora ramorum


NOTE: Phytophthora ramorum has now been added to the EPPO A2 List. A full datasheet is being prepared, in the meantime you can view here the data which was previously available from the EPPO Alert List.

Why: Sudden oak death came first to our attention as significant tree mortality has been observed on several oak species in California (US). A new species Phytophthora ramorum was found associated with the disease and considered as the primary causal agent. P. ramorum was also found in Europe on nursery plants (mainly Rhododendron, Viburnum) causing twig dieback but has never been found causing extensive damage in forests. Genetic studies have shown that USA and European populations belong to the same species P. ramorum. At first, different mating types were found in Europe (A1) and North America (A2), but in 2003 the occurrence of a few isolates belonging to A1 and A2 mating types was respectively reported in North America and Europe. It is hypothetized that the pathogen was separately introduced into these two regions from a third area which remains unknown.
Note: An EPPO diagnostic protocol is now available (with figures).
Phytophthora ramorum
Rhododendron shoot tip wilt
caused by Phytophthora ramorum

North America: Sudden oak death has only been reported in USA, in central coastal areas of California and one county in Oregon: California (counties of Alameda, Contra Costa, Humbolt, Lake, Los Angeles, Marin, Mendocino, Monterey, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, Sonoma), Oregon (county of Curry). In ornamental nurseries, infections have reported in several states: California, Georgia, Louisiana, Oregon, South Carolina, Tennessee, Washington. In Canada, it was detected in 2003 on 1 Rhododendron plant in a nursery (British Columbia), under eradication.
EPPO region: P. ramorum has been found mainly on Rhododendron and Viburnum in nurseries in Belgium, Croatia, Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Lithuania, Netherlands, Norway, Poland, Serbia, Slovenia, Spain (Asturias, Galicia, Islas Baleares: Mallorca), Switzerland, Sweden, United Kingdom. Since November 2002, emergency measures have been taken by EU Member States to avoid introduction and spread of P. ramorum.

On which plants:Sudden oak death has been observed on: Lithocarpus densiflorus (tanoaks), Quercus agrifolia (coast live oak) and Q. kellogii (black oaks), Q. parvula var. shrevei. These oak species are native to California. The pathogen was found on Vaccinium ovatum causing twig dieback. In California, P. ramorum has been found in rhododendron plants adjacent to infested oaks. The fungus was also isolated from Sequoia sempervirens and Pseudotsuga menziesii. Symptoms were limited to young and small branches and no mortality of mature trees was observed. P. ramorum was found on: Acer macrophyllus, Aesculus californica, Arbutus menziesii, Arctostaphylos manzanita, Heteromeles arbutifolia, Lonicera hispidula, Rhamnus californica, Rosa gymnocarpa, and Umbellularia californica, although its pathogenicity has not been yet demonstrated on these species. More recently, the following species were reported as hosts in USA: Quercus chrysolepis, Toxicodendron diversilobatum, Rubus spectabilis, Rhamnus purshiana, Corylus cornuta, Pittosporum undulatum, Trientalis latifolia. In Europe, P. ramorum is mainly found on Rhododendron and Viburnum, but it was also isolated from Arbutus, Camellia, Hamamelis, Kalmia, Leucothoe, Magnolia, Pieris, Syringa and Vaccinium myrtillus. An isolated finding on one Quercus falcata tree was reported by UK in November 2003, and shortly after on a few trees of Fagus sylvatica, Quercus ilex, Q. cerris, Castanea sativa and Aesculus hippocastanum. In the Netherlands, one infected tree of Q. rubra, and two Fagus sylvatica have also been identified (all trees were located near infected Rhododendron). In Ireland, P. ramorum has been isolated from one Q. phillyraeoides tree. In summer 2009, P. ramorum was detected for the first time on conifer trees (Larix kaempferi) in the United Kingdom. Since this initial discovery, large numbers of infected L. kaempferi have been observed in South West England. Other coniferous species have also been reported to be infected by P. ramorum  (e.g. Chamaecyparis lawsoniana). Ireland has detected the pathogen on a single Picea sitchensis (Sitka spruce).In California (US), there are isolated records of P. ramorum on Abies magnifica and A. grandis growing near infected Umbelluraria californica.

Damage: In North America, symptoms vary slightly between tree species. In L. densiflorus, wilted shoots are usually observed as the first symptoms. Older leaves become pale green and 2 to 3 weeks later the foliage turns brown, announcing the death of the tree. On the lower portion of the trunk, a burgundy-red to black sap oozing (bleeding) appears on the bark surface. In Q. agrifolia and Q. kellogii, the earliest symptom is usually the sap oozing. Sunken or flattened cankers are observed beneath the bleeding with a distinctive dark red canker margin in the bark and outer sapwood. In Europe, P. ramorum mainly causes leaf and twig blight.

Transmission: Infection would occur through zoospores, sporangia and chlamydospores. As for other Phytophthora, it is likely that the disease can be transmitted by infected plants and soil. However, it has also been observed that sporangia of the pathogen are deciduous which opened the possibility that they could be transported by air currents but this has not been demonstrated. Bark beetles and ambrosia beetles are commonly found on diseased trees but their potential role of vectors has not been studied yet.

Pathway: Plants for planting, wood, bark of L. densiflorus (tanoaks), Q. agrifolia (coast live oak) and Q. kellogii, soil from areas where the disease occurs. Plants for planting of ornamental hosts (e.g. Rhododendron, Viburnum) and of Vaccinium from areas where the disease occurs.

Possible risks: Oaks are important forest and amenity trees in the EPPO region. In USA significant oak tree mortality is observed, but not in Europe. Studies have been initiated on the susceptibility of European oak species to the disease, but no conclusion can be given yet. Nursery plants such as Rhododendron, Viburnum, are widely grown in the EPPO region and P. ramorum affects their quality. From experience with other Phytophthora diseases, control is difficult in practice. As a consequence of tree mortality, it was felt in USA that the disease could also have a negative impact on the biological diversity of forests and lead to environmental problems (enhanced fire risk and damage to water catchments). More data is needed on the identity, biology, host range, geographical distribution and epidemiology of the pathogen. In particular, further comparison studies between USA and European populations are needed to understand why observed situations are so different between the two regions.

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Anonymous (2007) Incidencia de plagas y enfermedades en las Comunidades Autónomas en 2006. Phytoma-España no. 187, 19-52 and no. 188, 16-56.
Anonymous (2007) Phyto Région. Pays-de-la-Loire. Phytophthora ramorum passe sur if et lilas. Phytoma – La Défense des Végétaux No. 607, p 3.
Annual Report 2001, Diagnostic Centre, Plant Protection Service, 135 pp.
Appel, D.N.; Kurdyla, T.; (2004) Nursery survey for sudden oak death in Texas (S5). Abstracts of the APS Annual Meeting, Anaheim, US, 2004-07-31-08/04. Phytopathology, 94(6), supplement of June 2004, 180 pp.
Běhalová M (2006) Surveys for Phytophthora ramorum in Czech Republic. Bulletin OEPP/EPPO Bulletin, 36(2), 393-395.
Benson, D.M.; Warfield, C.Y. (2004) Phytophthora ramorum not detected in a survey of North Carolina nurseries (S7). Abstracts of the APS Annual Meeting, Anaheim, US, 2004-07-31-08/04. Phytopathology, 94(6), supplement of June 2004, 180 pp.
Brasier, C.; Rose, J.; Kirk, S.; Webber, J. (2003) Pathogenicity of Phytophthora ramorum isolates from USA and Europe to bark of European forest trees (Abstract 11.23 of a paper presented at the 8th International Congress of Plant Pathology, Christchurch, New Zealand (2003-02-02/07).
Brasier C, Webber J (2012) Natural stem infection of Lawson cypress (Chamaecyparis lawsoniana) caused by Phytophthora ramorum. New Disease Reports 25, 26.
Brasier C, Webber J (2010) Sudden larch death. Nature 466(12), 824-825.
Bulajić A, Jović J, Krnjajić S, Djekić I, Krstić B (2008) First report of Phytophthora ramorum on Rhododendron sp. in Serbia. New Disease Reports vol. 18 (August 2008 to January 2009)
Chastagner, G.A.; Hansen, E.M.; Riley, K.L.; Sutton, W. (2004) Susceptibility of conifer shoots to infection by Phytophthora ramorum (S16). Abstracts of the APS Annual Meeting, Anaheim, US, 2004-07-31-08/04. Phytopathology, 94(6), supplement of June 2004, 180 pp.
Chastagner GA, Riley KL (2010) First report of Phytophthora ramorum infecting California red fir in California. Plant Disease 94(9), p 1170.
Davidson, J.M.; Garbelotto, M.; Koike, S.T.; Rizzo, D.M. (2002) First report of Phytophthora ramorum on Douglas-Fir in California. Plant Disease 86(11), 1274.
De Merlier, D.; Chandelier, A.; Cavelier, M. (2003) First report of Phytophthora ramorum on Viburnum bodnantense in Belgium. Plant Disease, 87(2), p 203.
Giltrap PM, Hugues KJD, Barton VC, Hobden E, Barber P, Izzard K (2007) Phytophthora ramorum on three new hosts detected using on-site diagnostics. Plant Pathology 56(4), p 728.
Gullino, C.; Garofalo, M.C.; Moretti, F.; Gianetti, G.; Mainenti, E. (2003) [Discovery of Phytophthora ramorum on rhododendron.] Informatore Agrario, 59(19), 87-89 (abst.).
Heiniger, U.; Theile, F.; Stadler, B. (2004) [First finding of Phytophthora ramorum in Switzerland.] Schweizerische Zeitschrift für Forstwesen, 155(2), 53-54 (abst.).
Hayden KJ, Rizzo D, Tse J, Garbelotto M (2004) Detection and quantification of Phytophthora ramorum from California forest using a real-time polymerase chain reaction assay. Phytopathology, 94(10), 1075-1083.
Herrero ML, Toppe B, Brurberg MB (2011) First report of Phytophthora ramorum causing shoot dieback on bilberry (Vaccinium myrtillus) in Norway. Plant Disease 95(4), p 335.
Herrero ML, Toppe B, Klemsdal SS, Stensvand A (2006) First report of Phytophthora ramorum in ornamental plants in Norway. Plant Disease 90(11), p 1458.
Hüberli D, Ivors KL, Smith A, Tse JG, Garbelotto M (2005) First report of foliar infection of Maianthemum racemosum by Phytophthora ramorum. Plant Disease 89(2), p 204.
Hüberli, D.; Reuther, K.D.; Smith, A.; Swain, S.; Tse, J.G.; Garbelotto, M. (2004) First report of foliar infection of Rosa gymnocarpa by Phytophthora ramorum. Plant Disease, 88(4), p 430.
Maloney, P.E.; Rizzo, D.M. (2002) First report of Phytophthora ramorum on Coast Redwood in California. Plant Disease 86(11), 1274.
Kroon LPNM, Verstappen ECP, Kox LFF, Flier WG, Bonants PJM (2004) A rapid diagnostic test to distinguish between American and European populations of Phytophthora ramorum. Phytopathology, 94(6), 613-620.
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Husson C, Delatour C, Frey P, Marçais B, Saurat C, Schenck N (2007) First report of Phytophthora ramorum on ornamental plants in France. Plant Disease 91(10), p 3159.
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Jovaišienė Z, Lane C (2006) First report of Phytophthora cactorum in Lithuania. Botanica Lithuanica 12(3), 197-199.
Lilja A, Rytkönen A, Kokkola M, Parikka P, Hantula J (2008) First report of Phytophthora ramorum and P. inflata in ornamental rhododendrons in Finland. Plant Disease 91(8), p 1055.
Moralejo, E. (2002) First report of Phytophthora ramorum on Rhododendron sp. in Spain. Plant Disease 86(9), 1052.
Pintos Varela, C.; Mansilla Vázquez, J.P.; Aguín Casal, O. (2004) Phytophthora ramorum nuevo patógeno en España sobre Camellia japonica y Viburnum tinus. Boletín de Sanidad Vegetal – Plagas, 30(1), 97-111.
Orlikowski LB (2004) Chemical control of Rhododendron twig blight caused by Phytophthora ramorum. Journal of Plant Protection Research, 44(1), 41-46.
Rizzo, D. (2002) Sudden oak death. Paper presented at the 13th USDA Interagency Research Forum on gypsy moth and other invasive species, Annapolis, Maryland, USA, 2002-01-15/18.
Riley KL, Chastagner GA, Blomquist C (2010) First report of Phytophthora ramorum infecting grand fir in California. Plant Health Progress April 2011 (public summary).
Shishkoff N (2012) Susceptibility of some common container weeds to Phytophthora ramorum. Plant Disease 96(7), 1026-1032.

Tooley PW, Martin FN, Carras MM, Frederick RD (2006) Real-time fluorescent polymerase chain reaction detection of Phytophthora ramorum and Phytophthora pseudosyringae using mitochondrial gene regions. Phytopathology 96(4), 336-345.
Tsopelas P, Paplomatas E, Tjamos SE, Soulioti N, Elena K (2011) First report of Phytophthora ramorum on Rhododendron in Greece. Plant Disease 95(2), p 223.
Vettraino AM, Hüberli D, Swain S, Bienapfl JC, Smith A, Garbelotto M (2006) First report of infection of maiden-hair-fern (Adiantum jordanii and A. aleuticum) by Phytophthora ramorum in California. Plant Disease 90(3), p 379.
Von Broembsen, S.L.; Olson, B.R.; Schnelle, M.A. (2004) Surveys of Oklahoma ornamental nurseries for Phytophthora ramorum the cause of sudden oak death (S106). Abstracts of the APS Annual Meeting, Anaheim, US, 2004-07-31-08/04. Phytopathology, 94(6), supplement of June 2004, 180 pp.
Winton, L.M.; Hansen, E.M. (2001) Molecular diagnosis of Phytophthora lateralis in trees, water, and foliage baits using multiplex polymerase chain reaction. Forest Pathology, 31(5), 257-320.
EPPO Secretariat (questionnaire), 2003-06.
NPPO of Austria, 2005-04.
NPPO of Belgium, 2005-01.
NPPO of Croatia, 2011-11.
NPPO of Czech Republic (2011-09, 2013-07).
NPPO of Estonia, 2004-11.
NPPO of Finland, 2012-11, 2012-12.
NPPO of Germany, 2002-05, 2003-03 and 2004-09.
NPPO of Ireland (2010-07, 2010-08, 2011-04).
NPPO of Italy (Emilia-Romagna, 2005-03; 2013-06).
NPPO of Latvia, 2004-09.
NPPO of Lithuania, 2007-11.
NPPO of the Netherlands, 2006-06.
NPPO of Poland, 2002-02 and 2004/06.
NPPO of Slovakia, 2004-11.
NPPO of Slovenia, 2003-11.
NPPO of Sweden, 2002-12.
NPPO of United Kingdom, 2003-11 and 2004-02.
Abstracts of papers and posters presented at the Sudden Oak Death Science Symposium – The state of our knowledge (Monterey, US, 2002-12-15/18)
BBA, DE - An unknown Phytophthora species on Rhododendron and Viburnum by Dr S. Werres.
Canadian Food Inspection Agency News Release (2003-06-13) Sudden oak death discovered at B.C. nursery
DEFRA (GB) - Sudden oak death, rhododendron shoot canker and viburnum dieback.
…Plant Health News… 21 May 2002-05-24.
News Release of 2002-05-03.
News Release of 2003-04-16.
Forestry Commission and DEFRA News Release of 2003-11-05. First infected oak found in Sussex.
Current situation – Phytophthora ramorum.
Joint Forestry Commission and DEFRA News Release of 2003-12-04. Phytophthora ramorum: more resources and new disease confirmations.
Forestry Commission and DEFRA News Release of 2004-02-01. ramorum disease: update.
Forestry Commission (GB). Phytophthora ramorum.
Phytophthora ramorum in larch trees – Update.

Direzione Generale Agricoltura. Regione Lombardia. Phytophthora ramorum Werres, De Cock & Man in ‘t sp. nov.
EPPO website. Presentations made at the EPPO Conference on Phytophthora ramorum and other forest pests, Falmouth, Cornwall, GB, 2005-10-05/07.
NAPPO Alert List - Phytophthora ramorum.
NAPPO Pest Alert – Official notifications. Sudden Oak Death (SOD), Phytophthora ramorum, first detection in Washington State – 06/12/2003.
NAPPO Pest Alert. News Stories: Sudden Oak Death (Phytophthora ramorum) detected in five Georgia Nurseries & Sudden Oak Death (Phytophthora ramorum) discovered in three Florida nurseries (2004-04-14 & 2004-04-05).
NAPPO Pest Alert. Official Pest Reports - Sudden Oak Death Syndrome in California Nurseries (2004-03-17).
Oregon Department of Agriculture Sudden Oak Death Alert:
Servizio Fitosanitario Emilia-Romagna. Prima segnalazione in Italia di Phytophthora ramorum.
University of California (several pages)
Sudden Oak Death Research Team Updates:
Cooperative Extension Sudden Oak Death:
Press Release of 2001-10-01. UC researchers announce results that could complicate measures to halt spread of Sudden Oak Death by C. Zandonella.
Monthly reports of the California oak mortality task force.
Observations and comments on oak and tanoak dieback and mortality in California by Tedmund J. Swiecki (2000-10-19):
California oak mortality task force website.
USDA-APHIS website
Plant disease caused by Phytophthora ramorum. A national strategic plant for USDA (2005-09-15).
APHIS. Pest detection and management programs – Phytophthora ramorum. Program update 2005-11-16.


EPPO RS 2001/002, 2001/115, 2001/204, 2002/019, 2002/020, 2002/040, 2002/077, 2002/078, 2002/160, 2003/014, 2003/019, 2003/020, 2003/037, 2003/038, 2003/039, 2003/040, 2003/041, 2003/078, 2003/079, 2003/133, 2003/134, 2003/145, 2003/146, 2003/161, 2003/162, 2004/024, 2004/053, 2004/054, 2004/086, 2004/105, 2004/106, 2004/107, 2004/136, 2004/139, 2004/150, 2004/151, 2004/171, 2004/172, 2005/036, 2005/037, 2005/050, 2005/072, 2005/158, 2005/159, 2005/160, 2005/161, 2005/162, 2006/025, 2006/076, 2006/102, 2006/211, 2007/095, 2007/107, 2007/137, 2007/177, 2007/178, 2007/188, 2007/210, 2008/031, 2008/127, 2009/113, 2010/033, 2010/149, 2010/150, 2011/003, 2011/111, 2011/112, 2011/113, 2011/223, 2011/244, 2012/014, 2012/078, 2012/193, 2013/014, 2013/130, 2013/146, 2013/147


Panel review date -
  Entry date 2001-01


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