Phytophthora ramorum belongs to fungus-like microorganisms (Oomycetes) and causes SOD (Sudden Oak Death). SOD has caused major damage in oak forests in the usa (California, Oregon). SOD also occurs in Europe. In the United Kingdom Phytophthora ramorum killed large numbers of Japanese larch trees (Larix kaempferi).
The fungus spreads primarily through splashing (rain) water and through transport of contaminated plant material and soil. The fungus can survive in the soil for more than a year and even nearly two years in shredded green waste. The fungus thrives in shady areas with high humidity.
Not only Quercus species can be affected by Phytophthora ramorum, but also rhododendrons, viburnum and pieris, among others.
After damage, recovery is no longer possible. Destroy infested shrubs and trees. Do not plant species susceptible to Phytophthora ramorum on the empty spots for the first three years after grubbing up.
Ensure that sun and wind have free access to trees and shrubs susceptible to Phytophthora ramorum.