Phytophthora oak decline; Root rot - Phytophthora quercina

EEffective: August 18, 2010 - December 31, 2019
Resources: Pest Tracker CAPS Pest Datasheet
Screening Aids:
Taxonomic Position: Peronosporales : Pythiaceae
Pest Type: Fungi
Pest Code (NAPIS): FGANPYC
This pest is a member of the following lists:

Oak
These Approved Methods are appropriate for: 2019, 2018, 2017, 2016, 2015
Pest is vectored by:
No known vector.
Survey
Approved Method(s):
Method Instructions NAPIS Survey Method
Water Sample In situ water sampling with rhododendron leaf baits (preferred method). See details below. 3014 - General Water Sample
Visual Collect soil or root sample from symptomatic trees. 3031 - General Visual Observation
Survey Instruction Details:
Use rhododendron leaves as bait by cutting the leaves in a herringbone pattern. Place 3-4 cut leaves into a mesh bag. Place the mesh bag into the water source for a minimum of 48 hours to 1 week (preferable).
Signs:
No specific signs are present.
Symptoms:
Twig abscission, epicormic shoots, crown thinning, branch and crown dieback, reduced growth, yellowing leaves.
Key Diagnostics


ID/Diagnostic: Multiple

Serological: An ELISA of dipstick test is available for Phytophthora at the genus level for primary screening. A positive does not indicate P. quercina.

ID must be confirmed by other methods.

Morphological:
1.Baiting technique (soil):

a.Submerge a rhododendron leaf, oak leaflet in soil sample. Cover with water. Remove baits after 48 hrs. Examine for lesions after 7 days.

b.Species are identified morphologically (Jung et al., 1999).

2.Direct Isolation (bark/roots):

a.Place pieces of tissue on semi-selective media.

b.Species are identified morphologically (Jung et al., 1999).
Mistaken Identities:
Symptoms of P. quercina are not characteristic as they are common for other forest Phytophthora species.
In Progress / Literature-based Diagnostics:
Molecular: PCR has been used to detect P. quercina in leaves. Nested PCR has been used to detect P. quercina in soil and water samples (Schubert et al., 1999; Nechwatal et al., 2001). Real-time PCR: method has been developed that uses two universal primers and a probe to monitor the quality of DNA extracted from environmental samples followed by a multiplex real-time PCR to detect P. quercina, P. ramorum, P. kernoviae, and P. citricola from symptomatic leaves (Schena et al., 2006). Schena et al. (2008) developed a PCR-based molecular tool box that could identify 15 Phytophthora species that damage forests and trees. Single-strand conformation polymorphism (SSCP) analysis of PCR-amplified ribosomal DNA internal transcribed region I has now been used to identify and provide a molecular fingerprints for 59 Phytophthora species, including P. quercina (Gallegly and Hong, 2008).
Notes:
P. quercina was reported from Missouri; however, the identification was never validated molecularly or verified by APHIS (Schwingle et al., 2007).
References
  1. Gallegly, M.E., and Hong, C. 2008. Phytophthora: Identifying species by morphology and DNA fingerprints. The American Phytopathological Society. APS Press.
  2. Jung, T., Cooke, D.E.L., Blaschke, H., Duncan, J.M., and Osswald, W. 1999. Phytophthora quercina sp. nov., causing root rot of European oaks. Mycological Research 103(7): 785-798.
  3. Nechwatal, J., Schlenzig, A., Jung, T., Cooke, D.E.L., Duncan, J.M., and Osswald, W.F. 2001. A combination of baiting and PCR techniques for the detection of Phytophthora quercina and P. citricola in soil samples from oak stands. Forest Pathology 31: 85-97.
  4. Schena, L., Duncan, J.M., and Cooke, D.E.L. 2008. Development and application of a PCR-based 'molecular tool box' for the identification of Phytophthora species damaging forests and natural ecosystems. Plant Pathology 57: 64-75.
  5. Schena, L., Hughes, K.J.D., and Cooke, D.E.L. 2006. Detection and quantification of Phytophthora ramorum, P. kernoviae, P. citricola, and P. quercina in symptomatic leaves by multiplex real-time PCR.
  6. Schubert, R., Bahnweg, G., Nechwatal, J., Jung, T., Cooke, D.E.L., Duncan, J.M., Muller-Starck, G., Langebartels, C., Sandermann, H., Jr., and Osswald, W. 1999. Detection and quantification of Phytophthora species which are associated with root-rot diseases in European deciduous forests by species specific polymerase chain reaction. European Journal of Forest Pathology 29: 169-188.
  7. Schwingle, B.W., Juzwik, J., Eggers, J., and Moltzan, B. The American Phytopathological Society. May 2007. Phytophthora Species in Soils Associated with Declining and Nondeclining Oaks in Missouri Forests.