SACRAMENTO-Today researchers, along with the California Department of Food and Agriculture (CDFA), announced the addition of Humboldt and Contra Costa Counties to the list of 10 counties* already known-to be-infested with Sudden Oak Death, bringing the total number of affected counties to 12.

The two leading researchers, Dave Rizzo, UC Davis associate professor and Matteo Garbelotto, UC Berkeley cooperative extension forest pathology specialist and adjunct professor of plant pathology, confirmed their findings through DNA analysis and laboratory culturing. The Contra Costa confirmations came from samples on California bay (Umbellularia californica) and coast live oak trees (Quercus agrifolia) in Wildcat Canyon while Humboldt County's came from California bay samples in the town of Redway.

As confirmed counties, Contra Costa and Humboldt will now fall under state and federal regulations, limiting the movement of host** plant material. Host plant material is defined as any part of a plant known to be susceptible to Phytophthora ramorum, the aggressive pathogen that causes Sudden Oak Death. Individuals within a regulated county must first have any movement of host plant material cleared through their local county agricultural commissioner.

For more information on Sudden Oak Death, visit the California Oak Mortality Web site at http://suddenoakdeath.org.

*Alameda, Marin, Mendocino, Monterey, Napa, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma
**California black oak, coast live oak, Shreve oak, tanoak, rhododendron, California bay laurel, big leaf maple, madrone, manzanita, huckleberry, California honeysuckle, toyon, California buckeye, California coffeeberry, and Arrow wood (in Germany, the United Kingdom, and the Netherlands)