Phytophthora ramorum
species of fungus
Phytophthora ramorum is the oomycete known to cause the disease sudden oak death (SOD). The disease kills oak and other species of trees and has had devastating effects on the oak populations in California and Oregon, as well as being present in Europe. Symptoms include bleeding cankers on the tree's trunk and dieback of the foliage, in many cases leading to the death of the tree.
P. ramorum also infects a great number of other plant species, significantly woody ornamentals such as Rhododendron, Viburnum, and Pieris, causing foliar symptoms known as ramorum dieback or ramorum blight. Such plants can act as a source of inoculum for new infections, with the pathogen producing spores that can be transmitted by rainsplash and rainwater.
P. ramorum was first reported in 1995, and the origins of the pathogen are still unclear, but most evidence suggests it was introduced as an exotic species to Europe and North America in separate events. Very few control mechanisms exist for the disease, and they rely upon early detection and proper disposal of infected plant material.
Presence
The disease is known to exist in California's coastal region between Big Sur (in Monterey County) and Del Norte County. It is confirmed to exist in all coastal counties in this range, as well as in all immediately inland counties from Santa Clara County north to Trinity County. It has not been found east of the California Coast Ranges, however.
The public source identifies “Phytophthora ramorum” as species of fungus. This brief keeps that definition visible, then builds a research path around Phytophthora, ramorum and species.
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Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Aug 17, 2026. The linked authority identifier is Q3382075. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1995.
Current terminology should not be projected backward without checking the classification used when the underlying evidence was created. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Phytophthora ramorum” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.