Steps to take to slow the spread of Sudden Oak Death Sudden Oak Death has killed thousands of stately oak trees in California. As its name implies, the onset of the disease and subsequent death of the oak is precipitous. First reported in Marin County in 1995, Sudden Oak Death is caused by a previously unknown pathogen species named Phytophthora ramorum (Pr). Usually Phytophthora are found in low-lying areas with lots of moisture. They first infest roots, spread through the plant, then progressing to the leaves. Recently, research has confirmed that Coast Redwoods and Douglas Fir are hosts to the disease. Infected redwoods have been found at Henry Cowell State Park among other sites. Trees dying from Pr. often are found on dry hills. Bay trees appear to be infected only in their leaves. Bay leaves can host so many spores that the spores cannot be counted, even with sophisticated equipment. No one knows where the disease originated. The genus Phytophthora includes the species that caused the Irish potato famine, causing some speculation that the disease came from Europe. Nor does anyone know what will be the final result of Sudden Oak Death. Little is known of the long-term ecology of forests, especially those in which substantial growth occurred after the advent of fire suppression at the turn of the last century. Dutch elm disease and chestnut blight took about 50 years to spread across the country and destroy those tree populations. How you can slow the spread of Phytophthora: Do not collect any plant material including leaves, flowers, acorns, twigs, wood and bark. Park your vehicle only in designated parking areas because spores may collect in mud on your tires and spread to other areas. Stay on established trails and respect trail closures. Avoid areas of damp soil or mud when walking, biking or horseback riding to prevent the pathogen from hitch-hiking. Clean soil and mud off shoes, bikes, vehicles and horse’s hooves to prevent spreading the contaminated soil. Clean woodworking tools with disinfectant. Visit this website for more information [ top of page ]

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