UC Berkeley students survey trees for sudden oak death. Photo: E. Loury

Ah, the signs of spring. The sun is out, the rain has stopped (for now)—and sudden oak death is on the move. This invasive, fungus-like tree killer, which is related to the Irish potato blight, moves in fits and spurts with bouts of warm spring rains. Every spring for the past four years, scientists from UC Berkeley have mobilized hundreds of volunteers to track the disease’s whereabouts in the Bay Area.

A bay leaf showing classic signs of sudden oak death. Photo: E. Loury

This massive citizen scientist effort is called a SOD Blitz (“SOD” for sudden oak death). “It started mostly as a way to engage people,” says organizer Matteo Garbelotto, a researcher at UC Berkeley who helped identify the disease-causing water mold, Phytophthora ramorum, in 2001. Because SOD outbreaks have a cyclical nature, they fall out of the news spotlight fairly quickly.  Garbelotto wanted to keep up public interest and awareness in the disease.  “When you actually do something, you look at it differently than just sitting in the chair and listening to even the brightest researchers in the world talking about it,” he says.

I recently attended the SOD Blitz at UC Berkeley, where Garbelotto briefed about 70 volunteers in how to spot the signs of the disease and collect data. The blitzes focus on bay laurel trees, which spread the disease to oaks without succumbing themselves, the way mosquitoes transfer malaria to people. Oaks can’t pass the disease to each other, so surveying bay trees provides the clearest picture of infection risks. The symptoms are also easy to spot on bay leaves. Garbelotto instructed the participants to look for brown leaf tips, where water droplets (and the water-borne disease) would accumulate. Other classic signs include a black line and yellow halo above the tip lesion, and little black specks throughout the leaf from disease carrying water droplets.

UC Berkeley student Heather Leslie collects leaves from a bay tree that shows symptoms of sudden oak death. Photo: E. Loury

I joined a pair of UC Berkeley students surveying the bay trees on a fire road behind the campus. The girls carried a collection packet of materials in a big manila envelope. When they spotted an infected bay tree, they jotted down its GPS coordinates (with the help of an iPhone ap), collected a handful of symptomatic leaves in a small envelope, and marked the tree with flagging tape.  They also made a note of any nearby oak trees that showed symptoms of the disease – which in oaks include bleeding bar and black opportunistic fungi.

Garbelotto’s lab will test all the collected leaves for the disease agent, and create a map of infected trees.  The maps can help homeowners decide whether their oaks might be at risk, and whether they ought to take steps to treat them. “When you combine all these maps, you have a really great distribution,” Garbelotto says. “There’s no way we can do it without the volunteers.”

If you care about oak trees in Santa Cruz, there’s a SOD Blitz coming up on Saturday, May 19 at10:30am. The location is the Cal-Fire Training Room on Gushee Street (behind the forestry office at 6059 Highway 9) in Felton. For more information, contact Nadia Hamey, nadiah@big-creek.com.  And you can find out about other SOD Blitzes throughout the Bay Area.  It’s a great way to spend a few hours outdoors and do something good for science!

Look for my feature in the upcoming edition of Science Notes this summer to get the full story on sudden oak death!

Citizen scientists collect data that will help researchers track the spread of sudden oak death. Photo: E. Loury