Sudden oak death

Sudden Oak Death' is the common name of a disease caused by the oomycete plant pathogen Phytophthora ramorum. The disease kills oak and other species of tree and has had devastating effects on the oak populations in California and Oregon as well as also being present in Europe.

Trees
Symptoms include bleeding cankers on the tree's trunk and dieback of the foliage, in many cases eventually leading to the death of the tree.

Other species
Characteristic symptoms are dark spots on foliage and in some hosts the dieback of the stems and twigs.

Treatment
Several effective compounds have been found; some of the most effective include mefenoxam, metalaxyl, dimethomorph, and fenamidone. Many of these studies have converged upon the following conclusions: chemical compounds are, in general, more effective as preventatives than in curatives; when used preventatively, chemical compounds must be reapplied at various intervals; and chemical compounds can mask the symptoms of P. ramorum infection in the host plant, potentially interfering with inspections for quarantine efforts.

Prevention
One of the most important aspects of P. ramorum control involves interrupting the human-mediated movement of the pathogen by ensuring that infested materials do not move from location to location. In most cases, cleanliness practices involve ridding potentially infested surfaces—such as shoes, vehicles, and pets—of foliage and mud before leaving the infested area.