Japanese oak wilt - Raffaelea quercivora
Effective: August 18, 2010 - December 31, 2020
Taxonomic Position: Ophiostomatales : Ophiostomataceae
Pest Type: Fungi
Pest Code (NAPIS): FGATRQE
This pest is a member of the following surveys: Oak
These Approved Methods are appropriate for: 2020, 2019, 2018, 2017, 2016, 2015
Pest Information
CAPS Pest Datasheet: https://download.ceris.purdue.edu/file/3631
Pest Tracker: https://pesttracker.org/pest/FGATRQE
Pest is vectored by:
Ambrosia Beetle (Platypus quercivorus) (Kubono & Ito, 2002).
Survey
Approved Method(s)
| Method | Detail | NAPIS Survey Method |
|---|---|---|
| Visual | Inspect host material. | 3031 - General Visual Observation |
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:
Tree crowns should be visually inspected for wilting leaves beginning in June through early September; leaves will appear curled or withered, then become discolored (reddish).
Wilted or dead oaks should be examined for evidence of attack by P. quercivorus: entrance holes, most dense within 1 m [~ 3 ft] of the ground and an accumulation of boring dust and frass at the base.
Wilted or dead oaks should be examined for evidence of attack by P. quercivorus: entrance holes, most dense within 1 m [~ 3 ft] of the ground and an accumulation of boring dust and frass at the base.
Key Diagnostic or Identification
Approved Method(s)
ID/Diagnostic:
Morphological: Identification will be based on the size and shape of conidiophores and conidia, and details of conidium production.
The colony is pale olive to brown and has a fragrance. The species is characterized by having small obovoid to pyriform sympodioconidia and slender, long conidiophores that taper to a point.
Raffaelea quercivora can be identified in the laboratory from the sapwood of an infected tree or log and from adult P. quercivorus. Surface sterilized pieces of discolored sapwood, insect galleries, adult beetles, and beetle mycangia can be plated on potato dextrose agar (PDA) with 100 ppm of streptomycin sulphate. Plates are incubated in the dark at 20-25�C (68-77�F) for five days.
For easier isolation, it is recommended to aseptically remove slices of galleries and place them in a sterile moist chamber to encourage further growth of the "ambrosia" fungus.
Note: Isolating Raffaelea quercivora is challenging. Contact the PPQ National Mycology Specialists (PPQNISNTMycology@usda.gov) prior to the start of the survey season. The mycology specialists will provide guidance on how to sample and isolate the fungus and review the laboratory requirements for successful isolation.
The colony is pale olive to brown and has a fragrance. The species is characterized by having small obovoid to pyriform sympodioconidia and slender, long conidiophores that taper to a point.
Raffaelea quercivora can be identified in the laboratory from the sapwood of an infected tree or log and from adult P. quercivorus. Surface sterilized pieces of discolored sapwood, insect galleries, adult beetles, and beetle mycangia can be plated on potato dextrose agar (PDA) with 100 ppm of streptomycin sulphate. Plates are incubated in the dark at 20-25�C (68-77�F) for five days.
For easier isolation, it is recommended to aseptically remove slices of galleries and place them in a sterile moist chamber to encourage further growth of the "ambrosia" fungus.
Note: Isolating Raffaelea quercivora is challenging. Contact the PPQ National Mycology Specialists (PPQNISNTMycology@usda.gov) prior to the start of the survey season. The mycology specialists will provide guidance on how to sample and isolate the fungus and review the laboratory requirements for successful isolation.
Mistaken Identities:
Oak anthracnose (Apiognomonia errabunda) and bacterial leaf scorch (Xylella fastidiosa), both present in the United States, can be confused with R. quercivora. Neither oak anthracnose or bacterial leaf scorch, however, cause the rapid mortality associated with the Japanese oak wilt pathogen.
Oak wilt caused by Ceratocystis fagacearum produces symptoms in red oaks over time that closely resemble those described for R. quercivora. Oak wilt is present in the United States.
Oak wilt caused by Ceratocystis fagacearum produces symptoms in red oaks over time that closely resemble those described for R. quercivora. Oak wilt is present in the United States.
References
If you are unable to find a reference, contact STCAPS@usda.gov. See the CAPS Pest Datasheet for all references.