Transmission
P. ramorum produces both resting spores (chlamydospores) and zoospores, which have flagella enabling swimming. P. ramorum is spread by air; one of the major mechanisms of dispersal is rainwater splashing spores onto other susceptible plants, and into watercourses to be carried for greater distances. Chlamydospores can withstand harsh conditions and are able to overwinter. The pathogen will take advantage of wounding, but it is not necessary for infection to occur.
As mentioned above, P. ramorum does not kill every plant that can be used as a host, and it is these plants that are most important in the epidemiology of the disease as they act as sources of inoculum. In the USA bay laurel seems to be the main source of inoculum in forests. Green waste, such as leaf litter and tree stumps are also capable of supporting P. ramorum as a saprotroph and acting as a source of inoculum. Because P. ramorum is able to infect many ornamental plants, it can be transmitted by ornamental plant movement.
Hikers, mountain bikers, equestrians, and other people engaged in various outdoor activities may also unwittingly move the pathogen into areas where it was not previously present. Those travelling in an area known to be infested with SOD can help prevent the spread of the disease by cleaning their (and their animal's) feet, tires, tools, camping equipment, etc. before returning home or entering another uninfected area, especially if they have been in muddy soil. Additionally, the movement of firewood could serve as a vector for sudden oak death, so both homeowners and travelers alike are advised to buy and burn local firewood.
Read more about this topic: Sudden Oak Death