UC forest pathologist Matteo Garbelotto’s Sudden Oak Death workshops are open to professionals and “homeowners”—unpaid tree companions?—alike. Garbelotto said, “As much as we work with the professionals, some people can’t afford a professional. I looked into the law. Almost everybody believes landowners can do it themselves. Tree-care professionals were not too upset. I got a sense the community was coming together to solve the problem.”
The legal skinny: Anyone who’s paid to apply pesticides has to be licensed after specific training and passing an exam. The law can be interpreted to include washing bugs off your client’s shrubbery with a water hose. On the other tentacle, a “homeowner” can pretty much apply all sorts of stuff without training; that’s one reason surveyors are still finding atrazine traces in urban creeks.
Garbelotto’s right, I think, about reasonable people’s general competence with the things that, so far, actually have positive results against SOD. “There are people out there selling snake oil,” he said. “[In the workshops] we debunk some alternative methods that have been sold. We’ve tested them and they don’t work.”
If your oak is surrounded by SOD vectors such as California bay laurel, there’s a way to bolster their hygiene, after pruning the carriers back to a 15–30 foot margin, if you can. Finely-ground dry commercial compost laid on the soil has been found to kill SOD spores. Calculate the splash distance to any part of the tree (about three feet) and mix in a thin layer once a year.
Another thing his lab has tested that works (to my surprise: the setup looks like some nutty pseudo-medical gimcrack) is dosing the tree with Agri-fos™ via spring-loaded injectors that reach the cambium.
Agri-fos is patented as a fungicide, but it looks a lot less scary than fungicides tend to be. Apparently it helps against Phytophthora species a well as fungi. (Fellow wonks will have noted that Phytophthora ramorum, the SOD organism, and its kindred are not fungi.) Australians developed the stuff to use against several plant diseases.
Garbelotto said that the compound is buffered phosphoric acid; the product flyer mentions “mono- and di-potassium salts of phosphorous acid.” Rather than killing organisms outright, it gooses a plant’s equivalent of an immune system to produce metabolites that resist the infection. That’s why it works against diseases to which a species hasn’t developed resistance.
The gadgety part is the injectors, which get stuck into small holes drilled just to the cambium (you can feel it, as resistance changes). They’re pricey too; it makes sense for a group to buy a set and the compound in bulk and then use them on the recommended schedule. Check the website.
You can spray Agri-fos™ combined with a surfactant, Pentra-Bark™, onto the treetrunk with a backpack sprayer, but the surfactant has more warnings on its label than Agri-fos™ does, and a spray gets misdirected more easily. Garbelotto says injections appear to be more effective than surface application, but the treatment regime he’s developed involves both.
Garbelotto’s hands-on demo is the easiest way to learn all this. If you can’t make the workshops, try the links from the lab’s website.
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 email@example.com, or call 847-5482. Register ASAP, as registration is on a first come-first serve basis, with a 20-person limit per session.