Mal del cipres; Cypress mortality - Phytophthora austrocedrae
Effective: March 13, 2020 - December 31, 2020
Taxonomic Position: Peronosporales : Pythiaceae
Pest Type: Fungi
Pest Code (NAPIS): FGANQQC
These Approved Methods are appropriate for: 2020
Pest Information
CAPS Pest Datasheet: https://download.ceris.purdue.edu/file/3625
Pest Tracker: https://pesttracker.org/pest/FGANQQC
Pest is vectored by:
No known vector.
Survey
Approved Method(s)
| Method | Detail | NAPIS Survey Method |
|---|---|---|
| Visual | Collect symptomatic plant tissue by visual survey. | 3031 - General Visual Observation |
Method Notes:
See the CAPS pest datasheet for detailed survey instructions.
Survey Recommendations
The following are recommendations for executing the survey using the approved methods for pest surveillance. The recommendations are developed through literature review and consultation with subject matter experts.
Signs:
No specific signs are present.
Symptoms:
Symptoms are similar in appearance in all known hosts. Above ground symptoms of infected trees include: foliage reddening or browning over all or most of the crown (Green et al., 2012), a progressive withering and defoliation, crown thinning, loss of radial growth, dieback, decay of main roots, and death of the tree, which remains standing or falls because of the wind. Trees may die rapidly. In this case, foliage changes from chlorotic (yellow) to red, or slowly, with chlorosis followed by progressive defoliation leading to tree death after several years (Filip and Rosso, 1999).
P. austrocedrae produces necrotic lesions that affect the entire thickness of the phloem, evidenced by discoloration of the tissue, and also induces superficial staining of the sapwood (Greslebin et al., 2007; Greslebin and Hansen, 2010). In A. chilensis trees, profuse resin production associated with the lesions is frequently observed.
P. austrocedrae produces necrotic lesions that affect the entire thickness of the phloem, evidenced by discoloration of the tissue, and also induces superficial staining of the sapwood (Greslebin et al., 2007; Greslebin and Hansen, 2010). In A. chilensis trees, profuse resin production associated with the lesions is frequently observed.
Key Diagnostic or Identification
Approved Method(s)
ID/Diagnostic:
1. Serological: An Enzyme-Linked ImmunoSorbent Assay (ELISA) Reagent Set for Phytophthora (AGDIA, Cat# SRA 92600/1000) at the genus level for primary screening. A positive does not indicate P. austrocedrae.
Identification must be confirmed by other methods.
2. Morphological: Samples of inner bark (phloem) tissue from lesion margins may be directly plated on a variety of selective media (PARNBP, PAR, NAR, BARP with a corn meal agar base and SMA + MRP1) immediately after collection or after washing necrotic tissue with running tap water for 24 to 48 hours (Greslebin et al., 2007; Green et al., 2012).
After initial isolation, colonies are transferred to a non-selective medium such as clarified V8 juice agar or tomato juice agar and stored for about six weeks at 16 to 17 C (60.8 to 62.5 F) in the dark until final identification can be made (Greslebin et al., 2007; Green et al., 2013). Greslebin (personal communication) found that much more growth occurred in media amended with beta-sitosterol. With media containing low or no sitosterol, sitosterol should be added to the medium.
3. Molecular: Real-time polymerase chain reaction (qPCR) is approved for species identification (see Notes).
Diagnostic Resources:
IDphy: molecular and morphological identification of Phytophthora, is a tool developed by PPQ in collaboration with Phytophthora experts that supports morphological and molecular identification of Phytophthora spp. including P. alni.
https://idtools.org/id/phytophthora/index.php
Identification must be confirmed by other methods.
2. Morphological: Samples of inner bark (phloem) tissue from lesion margins may be directly plated on a variety of selective media (PARNBP, PAR, NAR, BARP with a corn meal agar base and SMA + MRP1) immediately after collection or after washing necrotic tissue with running tap water for 24 to 48 hours (Greslebin et al., 2007; Green et al., 2012).
After initial isolation, colonies are transferred to a non-selective medium such as clarified V8 juice agar or tomato juice agar and stored for about six weeks at 16 to 17 C (60.8 to 62.5 F) in the dark until final identification can be made (Greslebin et al., 2007; Green et al., 2013). Greslebin (personal communication) found that much more growth occurred in media amended with beta-sitosterol. With media containing low or no sitosterol, sitosterol should be added to the medium.
3. Molecular: Real-time polymerase chain reaction (qPCR) is approved for species identification (see Notes).
Diagnostic Resources:
IDphy: molecular and morphological identification of Phytophthora, is a tool developed by PPQ in collaboration with Phytophthora experts that supports morphological and molecular identification of Phytophthora spp. including P. alni.
https://idtools.org/id/phytophthora/index.php
Mistaken Identities:
Disease symptoms caused by P. austrocedrae can be confused with other pathogens including other Phytophthora species. P. cinnamomi, a pathogen which is already present on a range of host plants in the United Kingdom (UK) and in the United States, can cause similar symptoms to P. austrocedrae on ornamental hosts. Physical damage caused by heavy snow or drought might result in similar browning of the foliage, but there would be no associated lesions (Forestry Commission, 2013). Phytophthora lateralis has been found to infect C. lawsoniana in the UK with similar host symptoms (Green et al., 2013).
Notes:
3/13/2020: The qPCR protocol uses the Cepheid SmartCycler thermocycler machine. In 2019, the manufacturer discontinued this machine. The S&T Beltsville laboratory is currently adapting the protocol for a different machine. Diagnostic labs may use the protocol for the Cepheid SmartCycler if their machine is in good condition. For the 2020 survey season, please contact the diagnostic laboratory you use for screening to confirm their capacity before you begin collecting samples.
References
- Filip, G.M., and Rosso, P.H. 1999. Cypress mortality (mal del ciprés) in the Patagonian Andes: comparison with similar forest diseases and declines in North America. European Journal of Forest Pathology 29: 89–96.
- Forestry Commission. 2013. Pests and Diseases - Phytophthora austrocedrae.
- Green, S., Brasier, C.M., Schlenzig, A., McCracken, A., MacAskill, G.A., Wilson, M., and Webber, J.F. 2013. The destructive invasive pathogen Phytophthora lateralis found on Chamaecyparis lawsoniana across the UK. Forest Pathology 43(1): 9-28
- 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.
- Greslebin, A.G. and Hansen, E.M. 2010. Pathogenicity of Phytophthora austrocedrae on Austrocedrus chilensis and its relation with mal del ciprés in Patagonia. Plant Pathology 59: 604-612.
- Greslebin, A.G., Hansen, E.M., and Sutton, W. 2007. Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina). Mycological Research 111: 308-316.
If you are unable to find a reference, contact STCAPS@usda.gov. See the CAPS Pest Datasheet for all references.