New survey shows rapid spread of Sudden Oak Death disease in California

Oct 16, 2016

A disease that kills oak trees along the California coast is spreading quickly and working its way south from Northern California, according to the most recent surveys done by the UC Berkeley SOD Blitz teams.

The details, just made public on Sunday, show Sudden Oak Death (SOD) is — for the first time — infecting areas of San Luis Obispo County.

Phytophthora ramorum, the pathogen behind the disease, has killed hundreds of thousands of native oak and tanoak trees in California over the last couple of decades.

Matteo Garbelotto is the person behind the UC Berkeley Sudden Oak Death volunteer tracking system. He told KCBX that water helps spread the disease, so the ongoing drought had slowed its growth in recent years, but that clearly changed this past spring.

“We had a lot of new findings that we didn’t really expect,” said Garbelotto. “And then, besides that, we also detected a very significant increase in the overall infection rates at the statewide level.”

The disease spreads through Bay Laurel trees, so it’s those trees that are sampled to determine the future growth of the infection area. Over the past several years, volunteers with Garbelotto’s program have been canvassing the state, picking leaves from laurels that show signs of the disease and then sending them into a lab for confirmation.

The 2016 survey shows an infected tree on the Cal Poly campus, in San Luis Obispo’s Irish Hills, and several groupings in rural areas just east of Cambria, and west of both Paso Robles and Atascadero.

(See the Google Earth mapping of the 2016 surveys)

Garbelotto said, while his survey is not official, it gives state authorities a big step up in narrowing the scope.

“So now there’s going to be some regulatory issues once the agencies confirm the infestation and so forth,” said Garbelotto. “At least we know that we have to look.”

Garbelotto says finding infected trees is the first step in controlling the problem as there are many steps that can be taken to reduce further spread. []