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 cinnamomi
Some chemical means of control include: fumigating and certain phosphonate fungistats. A tactic that may be effective, dependent on spores, would be fumigating before planting. However, this would not be effective for eradicating chlamydospores since they are present deeper down in the soil, so fumigation may not reach them. Some experts do not recommend fumigation as "P. cinnamomi" is often able to re-invade fumigated soil and could cause worse damage since the competing microorganisms in the soil microbial community may be reduced by fumigation. Phosphonate fungistats can improve the ability of a tree to tolerate, resist, or recover from disease by "Phytophthora cinnamomi". Phosphite has been used to limit the disease with some success and has been recognized as a major strategy for disease prevention. Phosphite is administered to plants through direct foliage sprays, aerial application by aircraft or through direct injection.