Sudden Oak Death
SAVING CALIFORNIA’S OAKS: Outreach Coordinator Janice Alexander
Glen Ellen, CA - In 1995, a strange malady appeared in Northern California. The leaves of oak trees turned brown. Trees collapsed.
While researchers scrambled to find out why one of the icons of California – its sprawling, ancient oak trees – were dying, people on whose land the trees grew frantically bought every touted bogus cure-all.
One of the jobs created when the California Oak Mortality Task Force organized in August 2000 was an outreach coordinator – a person who could act as the direct link between scientists and the public, to provide them with accurate information about the disease and how to grapple with it. The task force combined the efforts of the California Forest Pest Council and the California Department of Forestry and Fire Protection, which coordinate a coalition of research and education institutions, public agencies, non-profit organizations, and private companies.
“The first part of outreach occurred because there was such a huge, huge need,” says Janice Alexander, the task force’s sudden oak death outreach coordinator. “We had a lot of trees in highly populated counties and people didn’t know what was going on. People were out there trying to buy products,” to keep their trees from dying.
On this day, Alexander and her assistant, Deborah Zierten, walk through the forests of Jack London State Historical Park in Glen Ellen, California, on a quest for oaks infected with Phytophthora ramorum, the single-cell water mold that causes sudden oak death. Zierten is a graduate student at Southern Oregon University whose summer internship is funded by the Renewable Resources Extension Act (RREA), which is administered by UC’s Division of Agriculture and Natural Resources.
It doesn’t take Alexander and Zierten long to spot an infected tree: dark splotches on the bark of a tan oak deep in the forest indicate that this tree has been “bleeding”. The mold makes its way through natural openings in the trunk and infects the layer of tissue just beneath the bark. As it draws its nutrients from these cells, small dead spots appear. This canker grows and girdles the tree to slowly cut off the supply line from the roots to the crown.
The tree recognizes it’s infected, and tries to push out the invader by “bleeding” sap. The infection may spread through a tree slowly, over a couple of years, until one day, the tree strangles to death. No more nutrients make it to the leaves, which suddenly – within two or three days -- turn brown and lifeless. An ailing tree is susceptible to other attacks – by fungus or insects – that also may end up killing it.
California bay laurel trees are one of several plants that harbor the water mold. But they’re particularly important because they grow alongside oaks. The ends of their leaves turn dark brown, but the mold doesn’t kill them. “The pathogen tends to concentrate where water would collect on a leaf, so during rain or fog, the tips are where you see the infection,” says Alexander. Mold-laden water drips from laurel leaves to land on the trunks of oaks, and the infection begins.
When people ask Alexander how to determine if their trees are infected, “I always ask: ‘Where in the area are the California bay laurels?’ because that’s the way these trees get exposure to this pathogen,” she explains. Although other trees such as madrones also harbor the mold, laurels harbor many more spores.
During the early part of the epidemic, as hundreds of thousands of oaks were dying and the disease spread to 14 California counties, Alexander spent her time educating the public about sudden oak death. The task force put together a Web site with information about the disease – how to spot it, how to manage it, and how to report it – and publishes a monthly newsletter with the latest news about research, regulations, meetings and policy.
She also conducts field trips, which range from leading a group of researchers on an all-day trek into wild forest along the Big Sur coast, to herding school groups through an easily accessible forest, such as the one covering Jack London State Historical Park.
She and Zierten jump off the path to explore a patch of gnarled trees. “This is a coast live oak,” she says, patting the trunk of a 100-plus year-old tree. “Quercus agrifolia. When these trees started to show the symptoms and died, people really started paying attention. It’s a symbol of the California oak, these twisty branches that splay out everywhere. They’re great for kids climbing on it. When these trees die, it’s a big deal.”
They separate and walk from tree to tree. Alexander suddenly shouts out, and we come running. She points to the darkened trunk dotted with small hardened red drops. “This is a coastal live oak that’s got a very, very large canker with some really noticeable bleeding spots. They’ve actually dried and crystallized. It’s like a kind of lava glass.”
She points toward the branches, where the oak leaves are still green. “Who knows how long this has been infected,” she says. “Definitely there’s some fresh bleeding that’s been going on this past season. All surrounding this oak just above it here, this is all bay laurel.”
The tips of most of the laurel’s leaves are dark brown. “And that’s where the spores are coming from that are infecting this oak,” says Alexander, “just constantly dripping down right on the trunk, and the spores just worm their way in.”
So far, sudden oak death researchers have been able to develop a chemical to prevent the disease, but not cure it. Alexander’s job has shifted to helping people understand the distinction, and how important it is to carefully monitor their oak trees. “We also have this new kind of kink in the story that nursery plants – rhododendrons, camellias, and lilacs – can also be hosts for the pathogen. Because they’re shipped and traded all over the world and people commonly buy them and put them in their yards, they have to be aware that the pathogen might secretly be hitchhiking, and could be introduced in new areas.”
Does Alexander know if her outreach efforts have had any effect? “I wish I could say yes,” she laughs. “Last year, my RREA intern and I did a survey to figure out if our outreach was successful.” They determined that they could probably never be able to quantify the effects of their work. “What we can probably say is that we really helped with understanding the role of the nursery industry, and that has helped a lot of individual small infestations not get started.”
The task force has begun to see that some oak trees have a built-in resistance to the disease. “We’re not going to lose every oak in California,” says Alexander. “We’re eventually going to be able to replant with some of the more resistant varieties. But we still have to deal with the fact that lots of trees are dying now. And the tan oaks have much less resistance.”
And that’s her latest challenge: spreading the word about how the water mold is decimating tan oaks, and the importance of tan oaks in the forest ecosystem.
“That’s a bigger educational problem,” she says, because foresters treat tan oaks like weeds.”
- by Jane Ellen Stevens