WILD NEIGHBORS: Six-legged Guerillas

By Joe Eaton
Friday July 27, 2012 - 01:42:00 PM
Long-horned eucalyptus borer, an early suspect.
D. Hobern, via Wikimedia Commons
Long-horned eucalyptus borer, an early suspect.

Those of you who don’t listen to NPR either may have missed an intriguing story about the insects that have been attacking California’s eucalyptus trees, and how they may have gotten here. 

My thanks to Rusty Scalf for passing it along. 

Some background first. A couple of years ago I did a piece for another venue about butterflies in the East Bay Regional Parks. That led to an interview with park naturalist Chris Garcia at Ardenwood Historic Farm, where monarch butterflies roost in a bluegum eucalyptus grove every winter. 

“The trees are not in great shape,” she said. They’ve been attacked by waves of insects: first the long-horned eucalyptus borer (Phoracantha semipunctata), an Australian beetle; then the redgum lerp psyllid (Glycapsis brimblecombei), a scale-insect-like creature; most recently a couple of tortoise beetles (Trachymela sloanei and Chrysophtharta m-fuscum). “We’ve been dealing with that for many years,” Garcia added. “We had to cut down a whole bunch of trees. We’re also planting a lot of eucalyptus; we’re the only park in the District that plants them.” The Park District has attempted biological control: “Someone from Davis released a natural parasite, a wasp that attacks the larva of the long-horned borer. We got it under control. The psyllid, the one the kills the trees the most, came later.” 

According to the NPR story, at least one entomologist suspects the sequential arrival of those insects, all Australian natives like the eucalyptus, is no accident. His name is Timothy Paine, a professor at UC Riverside. He told the reporter he had begun to notice California eucs dying around 1985, and fingered the initial suspect: “We were working on the long-horned borer, and then another would come in, and another one would come in.” Paine has documented the arrival of 16 eucalyptus-pest species over the last 25 years. 

“If you see something one time, you accept it,” he said. “If you see another pattern, you wonder if it’s a coincidence. If you start seeing five or six different patterns that all point in the same direction, then you start to raise questions.” Paine’s question: were these insects deliberately introduced to California to kill eucalyptus trees? “We can’t imagine that it was done for any other reason.” 

It’s not difficult to identify a motive. Eucalypts, particularly the bluegum, have been called “giant weeds” by native-plant advocates. They’re highly flammable (bluegums and Monterey pines fueled the 1991 East Bay Hills fire); they’re messy; they discourage understory growth; their leaves smell like cat pee, which may be a desirable quality in a Sauvignon Blanc but can be annoying in a whole grove of trees. Even their timber is considered useless, although I’ve seen some handsome eucalyptus cabinetry. 

Over the years, federal, state, regional, and local agencies have promoted eucalyptus removal from public parks. Every such effort has drawn fire from euc advocates who grew up with the trees and think they look natural in the California landscape, wherever they might have come from originally. They are not without habitat value for native wildlife, as witness the Ardenwood dilemma. Raptors also roost and nest in them. 

But a guerrilla campaign to eradicate them by releasing six-legged saboteurs? Paine admits that he hasn’t found definitive proof: “You can find alternative explanations for all of this, no question about it. This is something we think is likely to have happened, but we don’t have a smoking gun.” 

Patterns are a tricky thing. We’re a pattern-perceiving species. Our brains are wired to connect the stars into dippers (or ploughs, or oddly long-tailed bears.) Seeing the face of Jesus in a grilled cheese sandwich or an oil stain is called pareidolia. Seeing sinister links between apparently unrelated events? Welcome to the happy world of the Truthers, the Birthers, the Intelligent Designers, the UFO abductees, and other conspiracy theorists, for whose worldviews paranoia is not too strong a word. (See Hofstadter’s classic The Paranoid Style in American Politics, which traces the phenomenon back to the Anti-Masons.) And paranoia can be comforting in a perverse way. Hey, the universe is not totally random after all! It’s out to get us, but there’s a structure, a plan, an order to it—even if it’s an evil order. Paranoia was a gold mine for Philip K. Dick, Thomas Pynchon, and a whole slew of other writers, not to exclude Dickens. 

I’m not saying Paine is clinically paranoid, of course. Science advances by recognizing patterns. Galileo, Newton, Darwin, Einstein, Watson and Crick all saw previously unsuspected patterns, and made the paradigms shift. The difference is that they had compelling evidence. 

Personally, I suspect that secrets are harder to keep than most conspiracy buffs will admit. What are the odds that a Johnny Bugseed who had been broadcasting Australian insects statewide for at least two decades would not have bragged about it somewhere on the Internet? But you never know.