CSLB C-27 Landscaping ContractorPlanting and LandscapingHard
A client notices a sudden, severe wilting of a mature oak tree, with leaves rapidly turning brown and remaining attached. Upon closer inspection, a distinct dark staining and streaking is visible in the sapwood just beneath the bark. This rapid decline suggests a serious disease. Which disease is most consistent with these symptoms?
- ASudden Oak Death (Phytophthora ramorum)
- BPowdery mildew
- COak root fungus (Armillaria mellea)
- DAnthracnose
Show answer & explanationAnswer & explanation
Correct answer: A. Sudden Oak Death (Phytophthora ramorum)
Sudden Oak Death (SOD) caused by Phytophthora ramorum is characterized by rapid browning and wilting of leaves that often remain attached, and distinct cankers with dark, tar-like exudate or staining in the inner bark/sapwood. This disease is highly aggressive and causes rapid tree decline, consistent with the scenario.
Why the other options are wrong
- B. Powdery mildew is a superficial fungal disease causing white powdery growth on leaves, not rapid wilting and internal staining.
- C. Oak root fungus typically causes slower decline, often with fungal fruiting bodies (mushrooms) at the base, and a white fungal mat under the bark, not distinct dark sapwood staining as described.
- D. Anthracnose causes leaf spots, blight, and cankers, but generally not rapid, severe wilting of an entire mature tree with distinct sapwood streaking.
Sudden Oak Death (SOD)
A lethal tree disease caused by the pathogen Phytophthora ramorum, primarily affecting oaks and tanoaks, characterized by rapid leaf browning, wilting, and cankers with dark sapwood discoloration.
- Rapid, severe decline.
- Leaves often remain attached.
- Distinct cankers with dark staining under bark.
- Caused by P. ramorum.
Memory trick: Rapid 'Sudden' death with 'dark' streaks means 'SOD' is the killer.