Sudden Oak Death (SOD) has been confirmed in Trinity County, Calif., according to the California Department of Food and Agriculture (CDFA). Phytophthora ramorum, the pathogen known to cause SOD, was first found by UC Cooperative Extension, Humboldt and Del Norte County personnel less than 600 yards over the Humboldt County line into Trinity County on an 80-acre Bureau of Land Management parcel adjacent to the Six Rivers National Forest. The nearest known infestation is 0.4 miles west in Humboldt County.
Infected California bay laurel and tanoak trees, spanning approximately a 5-acre area, were identified; however, ground surveys to delineate the actual extent of the infestation will not be conducted until spring 2014, when symptoms will be most advantageous for surveying. Symptoms found include dead and symptomatic tanoaks as well as heavily symptomatic bay trees. In California, California bay laurel as well as tanoak leaves support pathogen spore production and spread. Tanoak can also die from the infection once it spreads to the tree trunk.
Trinity County is now the fifteenth California county known to have SOD*. “CDFA has submitted and finalized an emergency regulation change adding Trinity County to California Code of Regulations 3700, Oak Mortality Disease Control,” said Jeff Dolf, Humboldt and Trinity County agricultural commissioner. As a regulated county, Trinity will be required to follow state and federal quarantine guidelines for the disease.
SOD is a serious invasive, quarantine disease that is killing tanoak, coast live oak, California black oak, Shreve’s oak, and canyon live oak trees in California. Since its discovery in 2000, more than 3 million trees have died, making it the number one cause of tree mortality in California coastal forests. In the last 2 years alone, more than 500,000 trees have died.
* Alameda, Contra Costa, Humboldt, Lake, Marin, Mendocino, Monterey, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, Sonoma, and Trinity Counties