The loss of these trees is both aesthetically and financially costly. Relatives of this novel fungus caused the Irish potato famine and are causing oak dieback in many parts of the world. Researchers must now search to understand the fungus' biology, its role in Sudden Oak Death, and what role, if any, bark beetles and other fungi consistently associated with the dying trees play. Symptoms In tanoak, leaf symptoms are usually the first to appear . New growth may droop or turn yellow to brown.
Droop occurs on most or all of the crown, rather than in a localized area.
Similar bleeding is also seen on tanoak. The species of Phytophthora isolated from dying oaks does not match any of the 60 known Phytophthora species in the world. At this time it is unknown whether the fungus was recently introduced into California or if it is a native and has only recently increased in importance as a tree-killer. The fruiting bodies of the Hypoxylon thouarsianum fungus may also be present. They are small, black domes.