Abstract
Sudden oak death, a disease associated with the pathogen Phytophthora ramorum, has a large number of shrub and tree host species. Three of the tree species most susceptible to mortality from the disease, California black oak (Quercus kelloggii), coast live oak (Quercus agrifolia), and tanoak (Lithocarpus densiflorus), are estimated to predominate by basal area on 1.52 (±0.10) million ac in 12 counties that currently are under quarantine for the disease. The variety, prevalence, and importance of host species to wildlife indicate a high potential for impact on forest ecosystems in California.