Protecting Trees from Sudden Oak Death before Infection

Phytophthora ramorum, an introduced invasive plant pathogen that causes sudden oak death, has killed over a million tanoak, coast live oak, Shreve oak, and California black oak trees along the California coastal region from Monterey through Humboldt Counties. Most trees infected with P. ramorum will eventually die, including prized landscape trees. Be aware that P. ramorum can infect California bay laurel trees in advance of oak and tanoak infection and that the symptoms of bay laurel infection are not obvious. This publication provides advice to landowners, land managers, arborists, foresters, and the general public about protecting trees from sudden oak death in areas where trees are not currently infected by P. ramorum, but where it is suspected that the pathogen will infect trees in the future because infested areas are nearby. Such areas might include, for example, those at the outer edges of the known infested areas in California. Other publications, such as the UC IPM publication Sudden Oak Death (Swain and Alexander, 2010), outline measures you can take to care for trees in areas where the pathogen is already known to be present on oaks and tanoaks. To determine whether this information is appropriate to your situation, review the next section for the best ways to find out whether your trees are already infected or whether infected trees exist in your area.