Oak Dieback

Phytophthora quercina
Last updated by:

Faith Campbell

As discussed in the Gallery page for Phytophthora alni, this pathogen is one of the emerging European threats to North American forests (Jung, et al. 2000; Jung undated). European oaks (Quercus robur & Q. petraea) have experienced waves of mortality due to unknown causes since the 1920s (Balci & Halmschlager 2002a). In the mid-1990s, a range of root-infecting Phytophthora species were shown to be associated with classic oak dieback (Brasier 2003). Several of the associated pathogens were species already well known to science, but some were new to science, including Phytophthora quercina (Brasier 2003). Several studies demonstrated the link between this newly detected pathogen and the dieback–including Jung et al. (1999) in Germany and Vettraino et al. (2002) in Italy. Some studies indicate that environmental factors also play a role in determining the virulence of the disease (e.g., Jönsson et al. (2003) in Sweden).

This dieback has now been found from Turkey to Scotland (Anonymous 2004). Known hosts include Quercus robur, Q. petraea and Q. pubescens (Balci & Halmschlager 2002b), Q. ilex, Q. pubescens, and Q. cerris (Blaschke et al. 1996).

The pathogen causes a disease of the tree’s fine feeder roots; loss of the roots leads to yellowing, crown thinning and eventual death of those trees (Anonymous 2004; Jönsson et al. 2003; Blaschke et. al. 1996).

Phytophthora quercina is quite adaptable with regard to site conditions; it can be found at dry sites that normally do not favor the survival of Phytophthora species (Balci & Halmschlager 2002b). Studies suggest that the pathogen is introduced and has most likely been spread via the forestry practices and plant trade (Anonymous 2004).

USFS scientists and managers developed a conservation priority-setting framework for forest tree species at risk from pest & pathogens and other threats. The Project CAPTURE (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) uses FIA data and expert opinion to group tree species under threat by non-native pests into vulnerability classes and specify appropriate management and conservation strategies. The scientists prioritized 419 tree species native to the North American continent. The analysis identified 15 taxonomic groups requiring the most immediate conservation intervention because of the tree species’ exposure to an extrinsic threat, their sensitivity to the threat, and their ability to adapt to it. Each of these 15 most vulnerable species, and several additional species, should be the focus of both a comprehensive gene conservation program and a genetic resistance screening and development effort.  Oak dieback is not known to be a threat to any of these 15 most vulnerable species.


Anonymous 2004. Population biology and speciation processes in forestry Phytophthoras. British Society for Plant Pathology. www.scri.sari.ac.uk/SCRI/web/site/home/ResearchAreas/MGOE/HPC/Population_Biology.asp. Accessed 12 December 1005.

Balci, Y. And Halmschlager, E. 2002a. First Confirmation of Phytophthora quercina on Oaks in Asia. Disease Notes Plant Disease. Vol. 86. No. 4 April 2002. www.apsnet.org/pd/searchnotes/2002/dapnotes.pdf

Balci, Y. and Halmschlager, E. 2002b. First report of Phytophthora quercina from oak forests in Austria. Accepted for on-line publication 22/08/02 www.apsnet.org/pd/searchnotes/2002/dapnotes.pdf Accessed 12 December 2005.

Blaschke, H. Jung, T., Osswald, W.F., Götz, B., and Matyssek, R. 1996 Mechanism of Phytophthora-induced decline of oaks in Europe. At www.forst.uni-muenchen.de/EXT/LST/BOTAN/INSTITUT/cost2.htm. Accessed 12 December 2005.

Brasier, C.M. 2003. Phytopthoras in European forests: Their rising significance. In Sudden Oak Death: How Concerned Should You Be? An International Online Symposium April 21 – May 12. 2003; at 44accessed December 9, 2005.

Jönsson, U., Jung, T., Rosengren, U., Nihlgard, B. and Sonesson, K. 2003. Pathogenicity of Swedish isolates of Phytophthora quercina to Quercus robur in two different soils. New Phytologist Volume 158 Issue 2 Page 355.

Jung, T. undated. Life cycle and pathological importance of the genus Phytophthora.

https://www.baumkrankheiten.com/docs-en/phytophthora.html, accessed March 2006.

Jung, T., Blaschke, H., and Osswald, W.F. 2000. Involvement of Phytophthora species in Central European oak decline and the effect of site factors on the disease. Plant Pathology 49: 706-718.

Jung, T., Cooke, D.E.L., Blaschke, H., Duncan, J.M., and Osswald, W. 1999. Mycological Research, 103: 785-798 Cambridge University Press. Published Online 08 Sep2000 at https://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=42867. Accessed 12 December 2005.

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S., Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/

Vettraino, M., Barzanti, G.P., Bianco, M.C., Raggazi, A., Carpetti, P., Paoletti, E., Luisi, N., Anselmi, N., and Vannini, A. 2002. Occurrence of Phytophthora species in oak stands in Italy and their association with declining oak trees. Forest Pathology. Volume 32:1, p19.