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 kernoviae
Since 2003, "Phytophthora kernoviae" has caused marked damage to ornamentals and species of trees in the Southwest United Kingdom. The oomycete pathogen was first discovered in the 1990s, yet only gained widespread attention when it was identified as one of the causal agents, along with "P. ramorum," of sudden oak death. Although the main concentration of this pathogen is primarily in South West England, its reach has extended to South Wales, Cheshire, and even further north into Scotland. Recently, this pathogen has been found on the steams and foliage of "Rhododendron", most significantly on "R. ponticum." Furthermore, the aggressive nature of "Phytophthora kernoviae" makes it an even more significant concern considering that the mainland of the UK has diverse ecosystems that are susceptible to the impact of this plant pathogen. From the "Rhododendron" host, infection is able to spread via the air to the bark of tree species, with the European beech tree ("Fagus sylvatica)" being especially susceptible. As of 2005, it was confined to a relatively small area of Cornwall but has also been found in Wales and Cheshire suggesting that the pathogen may be being spread by the horticultural trade. Due to the national and international demand of these plant products, "Phytophthora kernoviae" has initiated recent concern after being found "Vaccinium myrtillus", commonly called Bilberry. This pathogen causes significant necrosis on leaves, bleeding stem lesions, and stem dieback as the primary symptoms, which occur at an impressive rate. Countless species including "V. myrtillus", "V. vitis-idaea", "Arctostaphylos uva-ursi", and "Rhododendron ponticum" are all especially vulnerable to "P. kernoviae".