Lots of rain already! Good news vis-à-vis fire season, maybe bad news for our oaks. Sudden Oak Death (SOD) watchers worry that if this is an El Niño winter with lots of rain, the disease already devastating some of our keystone oak species will spread farther and faster.
Phytophthora ramosum, the disease organism, is one of those nasty critters that taxonomists find interesting: It’s not a bacterium or fungus, but a member, maybe, of a “kingdom”-level taxon that includes brown algae and slime molds. Whether this group really composes a fourth “kingdom” or is just a handy designation for what isn’t animal, plant, or fungus—there’s the academic fun of current debate.
Meanwhile, back in the woods, conditions are test-tube ideal to spread a disease whose sturdy little spores travel by water, including little splashes and dribbles. They also need water to wake up and live, infect, and reproduce.
SOD moves downhill with water, and also down to the lowest parts of leaves when it infects them. By the time you see wilting, browning, opportunistic fungus clusters, or bugs, the tree’s doomed.
The organism was doubtless introduced with some ornamental plant or other in the nursery trade. The trade had set up safeguards and maybe those will work, but this zebra’s out of the barn already and it kills most of the wild trees it infects, as far as we know.
Its zebrahood is part of the problem. The usual advice about tree diseases, to keep trees healthy enough to fight them off and recover, doesn’t work with this one because it’s hitting a naïve population. Remember how so many of the First Peoples here died of diseases that Europeans had adapted to survive—measles, assorted poxes? Like that.
Matteo Garbelotto notes, in fact, “Sometimes the most robust trees become most attractive and susceptible; they produce more carbohydrates for the Phytophorum to live on. The trees we see surviving are the scraggly ones.
“But we can’t stop keeping a susceptible tree happy. What we have to do is choose the trees we want to try saving, and by March or April, when most infection is happening, make those trees as invulnerable as possible.”
There are things that help, and they’re relatively accessible to ordinary people, and non-toxic to the rest of the world. Oak-lovers need to start on these early. There are also lots of quack remedies out there, no surprise, and some are expensive. Garbelotto’s UC lab has been trying out everything they’ve heard of, and most just don’t work.
His team is conducting “SOD blitzes” to find out where the disease exists now, mapping it on-line, and giving free hands-on workshops to tree-owners and professionals.
SUDDEN OAK DEATH
1-3 p.m. Wednesday, Nov. 4, and Wednesday, Dec. 9, 2009 at the Tolman Hall “Portico” on the UC Berkeley campus.
Admission is free, but registration is required. E-mail your name, preferred date, and affiliation (if applicable) to firstname.lastname@example.org, or call 847-5482. Register ASAP, as registration is on a first come-first serve basis, with a 20-person limit per session.
Next workshop: Sudden Oak Death Syndrome — what to look for and what to do.