10:48 am PST, Monday, November 11, 2019
Photo: David McNew/Getty Images
Sudden Oak Death (SOD), a deadly disease for oak trees, is on the rise in California. According to a survey conducted by UC Berkeley scientists, the number of infected trees has almost doubled since 2018.
Matteo Garbelotto, the director of the UC Berkeley Forest Pathology and Mycology Laboratory, has been involved in conducting the survey of 14 California counties (stretching from Humboldt to Monterey) for the past 12 years. This year, two aspects of the results stood out to him.
“We found this year the most sharp increase ever in the number of trees affected,” said Garbelotto. However, this was expected due to the wet winters we’ve had in California for the past two years — the spores spread faster with significant rainfall.
What was really unexpected was the scope of where they were finding the outbreaks.
“I saw a lot of outbreaks that we had seen before in the 12 years of our program, but I saw all the outbreaks being expressed at once this year,” he said. In previous years, some outbreaks would decrease while others would flare up — this year, every outbreak flared up. “This patterns shows me that the organism has really spread into the ecosystem of Coastal California. Now it’s already established everywhere, and it flares up when the weather is favorable. “
Other findings from the survey include a new outbreak in Del Norte County, which was up until now the only county between the vast California infestation and the Southern Oregon outbreak that was free of the disease. San Luis Obispo remains free of the disease, but is at high risk of infection. All San Francisco parks remain entirely uninfected.
While analyzed by UC Berkeley scientists, the data from the survey is 100-percent collected by volunteers. UC Berkeley goes to local communities were SOD is an issue, and trains local volunteers to identify the symptoms. This year’s results are particularly alarming, but Garbelotto sees one positive takeaway: “It’s kind of a testament to what you can achieve by working with volunteers.”
With the data readily available through a mobile app, people can identify the risk of trees in their vicinity and take precautions before it’s too late. The pathogen often spreads on the leaves of infected California bay laurel and tanoak, which can be easily identified.
“The infection of leaves always happens before the infection of oaks,” said Garbelotto. “Something can be done, but in order for that something to be effective, we need to do it before oaks have become affected.”
Proactive methods for controlling the disease include sanitation, chemical treatments, and the targeted removal of bay trees.
Staying on top of SOD is vital, as Garbelotto calls it “the scariest tree pathogen in the world” for two reasons: “The first one is how easily it reproduces, and secondly, its ability to affect other plants is very high locally.”
And keep in mind that the more dead trees left behind, the more kindling there is for wildfires.
Madeline Wells is an SFGATE digital reporter. Email: [email protected] | Twitter: @madwells22