Symptoms of Sudden Oak Death
Pepperwood (CA bay laurel, Umbellaria californica) and tanoak (Notholithocarpus densiflorus) are the two plant species known to spread the pathogen Phytophthora ramorum. As such, they are the two most important species to watch for symptoms of SOD.
The best identification resource for the north coast is the symptom ID introduction by Humboldt County UC Cooperative Extension.
The Garbelotto lab at UC Berkeley has put together an ID sheet showcasing leaf symptoms on both pepperwood and tanoak.
Phytophthora ramorum causes a leaf blight on pepperwood and does not kill the tree. Look for dead leaf tips with yellowing behind a black line.
The disease causes mortality in tanoak within two years of infection. Signs of infection include black lesions on the twigs, leaf die back originating in the petiole, dead branch tips, and bleeding cankers from the main tree stem.