Phytophthora ramorum
Trials of silvicultural methods for treating "P. ramorum" began in Humboldt County in northwest coastal California in 2006. The trials have taken place on a variety of infested properties both private and public and have generally focused on varying levels and kinds of host removal. The largest () and most replicated trials have involved removal of tanoak and bay laurel by chainsaw throughout the infested stand, both with and without subsequent underburning designed to eliminate small seedlings and infested leaf litter. Other treatments included host removal in a modified “shaded fuelbreak” design in which all bay laurel is removed, but not all tanoaks; bay and tanoak removal using herbicides; and removal of bay laurel alone. The results of these treatments are still being monitored, but repeated sampling has so far detected only very small amounts of "P. ramorum" in the soil or on vegetation in the treated sites.
Phytophthora ramorum
As mentioned above, "P. ramorum" does not kill every plant that can be used as a host, and these plants are most important in the epidemiology of the disease as they act as sources of inoculum. In California, California bay laurel ("Umbellularia californica") seems to be the main source of inoculum. Green waste, such as leaf litter and tree stumps, are also capable of supporting "P. ramorum" as a saprotroph and acting as a source of inoculum. Because "P. ramorum" is able to infect many ornamental plants, it can be transmitted by ornamental plant movement.