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.
Rhododendron album
Pseudomonas cichorii
In 1995, the bacteria "Pseudomonas cichorii" was discovered on container-grown rhododendrons in a nursery in Georgia, USA. The spots were at first very small, one to five millimeters in diameter, but soon grew into large, reddish brown blotches. (Uddin & McCarter, 1996).
Phytophthora ramorum
In 2002 and 2003, studies in nurseries throughout California and Oregon tested for "Phytophthora ramorum". The symptoms of the disease were large necrotic spots with water soaked outside borders and rust colored centers. Symptomatic plants were collected, and DNA was extracted from the spots. After amplifying it with a PCR assay, GenBank matched the DNA to that of "Phytophthora ramorum" and "P. lateralis". In 2004, Rhododendron leaves with similar symptoms were studied and showed the host range of P. hibernalis as well (Blomquist et al. 2005).