Sudden Oak Death is the common name of a disease caused by the oomycete plant pathogen Phytophthora ramorum. The disease kills oak and other species of tree and has had devastating effects on the oak populations in California and Oregon as well as also being present in Europe. Symptoms include bleeding cankers on the tree's trunk and dieback of the foliage, in many cases eventually leading the death of the tree. P. ramorum also infects a great number of other plant species, significantly rhododendrons, causing a non-fatal foliage disease known as ramorum dieback.
Please note: several new species have been added to the list of species affected by Sudden oak Death.
You will find the most up-to-date information and research at the California Oak Mortality Task force website:
Here two web links offering hope for the organic management of Sudden Oak Death and other tree dieback diseases (increasing soil fertility):
Excerpt: Applying his own theory to Sudden Oak Death, Zingaro fed his customers’ trees – those affected and also ones deemed “high-risk” – with a phosphite-based fertilizer, Bio-Serum, which he touted as a “tree tonic.” He also says he applied a combination of other minerals and rock dust, designed to address the problems with the soil. “The fertilizer was around for ages,” he points out about Bio-Serum, and it was legal to use for such purpose.