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.
Fungicide use in the United States
Crown and root rot of almonds is caused by at least 14 different "Phytophthora" species. The risk of root or crown infection is greatest during cool to moderate temperatures with prolonged or frequent soil saturation. A tree infected with "Phytophthora" can either undergo a period of slow decline that may last years or it can suddenly collapse and die in spring with the advent of warm weather. Eventually, leaves drop, terminal shoots die back, and death of the tree follows. Once in the root or crown the infection may extend into the crown, trunk, or branches. Currently, crown and root rot are a problem affecting 20% of California's almond orchards with potential yield losses of 50%.