Wasps Get Job of Saving Eucalyptus From Beetles

All over Rancho Santa Fe, you can hear the sound--the clatter of insatiable little insect mandibles devouring another tasty meal of bark and wood.

Some say the racket resembles falling rain. Or the crackle of Rice Krispies once the milk’s been poured on. One by one, the mighty eucalyptus trees that have become the very symbol of country living in this wealthy North County enclave are being eaten alive by millions of invading longhorn borer beetles from Australia.

For many residents, it’s “Them” all over again, a replay of the nightmarish 1950s sci-fi thriller about hordes of insects on the loose. Over the past few years, residents estimate, as many as 20,000 of the ranch’s 100,000 eucalyptus have fallen prey to the inch-long insects, which bore clean through the bark to lay their larvae, eventually choking off the tree’s life-giving flow of moisture.

“You can see the devastation by just driving around the Ranch,” said Walt Ekard, manager of the Rancho Santa Fe Assn., the community’s governing body. “So many trees are missing along the roadsides it looks like someone’s smile with half their teeth missing. And that’s just the public areas. Lots more trees are dying on private lots.”

Now, though, the ranch is fighting back. Recently, the Rancho Santa Fe board of directors voted to spend $20,000 to help fund a UC Riverside entomology study--becoming the first test community in the state to loose about 100 Australian wasps into its back yards in the hopes of finding a way to combat a bug problem that has so far vexed local exterminators and is growing worse with the drought.

If the program is a success, ranch officials say, they will authorize another $20,000 for each of the next two years.

The Syngaster lepidus wasp is a known natural predator of the borer beetle back home in Australia. And, although the beetle was brought here by accident a decade ago--probably in the wooden crates of a merchant marine vessel--the wasps have been brought here on purpose, scientists say, because the wasps use the beetle larvae as a host for development of their own young.

Scientists involved with the eucalyptus borer project also are busy breeding a second Australian wasp--of the genus Doryctes-- that they hope will be even more effective against the killer beetles.

In Rancho Santa Fe, the borers have become a rallying point. Everyone has been bugged by the ubiquitous beetles.

“This is just the first salvo against these fierce little creatures,” Jim Ashcraft, president of the ranch association’s board of directors, said of the wasp release project, which could begin as early as summer’s end.

“We figure this gives us at least a 5- to 10-year start on attacking the borers. Otherwise, we could have a situation here with a large percentage of our eucalyptus trees dead. And I don’t ever want to see that day come to pass.”

Scientists studying the beetles say the longhorned borers are not only a problem in Southern California but the rest of the state as well. The infestation has hit stately stands of eucalyptus in Carlsbad, Balboa Park and Scripps Ranch.

Recently, they said, the borers made their first appearance in the San Francisco Bay Area when more than 400 trees on the Stanford University campus were found to have been infested.

According to Dr. Larry Hanks, one of four scientists involved in the UC Riverside study, the beetles are chemically attracted to trees suffering stress from underwatering or other diseases.

“They’re spreading well into Northern California,” he said of the bugs. “If you have a tree that’s stressed, the adults will come and lay their eggs.”

Like an underground subway system, the tree soon is excavated by the tunneling borers, which deposit their eggs beneath its surface. As they develop into the larval stage, the beetles devour the tissue that conducts water throughout their host, fatally dehydrating the tree.

The recent drought, Hanks said, have accelerated the spread of the invading nocturnal beetles.

“Within a couple of weeks of their attack, the tree may look all right, but often it’s essentially dead where it stands,” he said. “Doomed.”

Within the past few weeks, the Riverside scientists have watched the beetles devastate three full-grown eucalyptus trees right outside their own campus after officials there neglected to water the trees for just 10 days.

The thing that stuck with him, Hanks recalled, was the sound of the beetle attack. “From 10 feet away, it sounded like rain or the snap, crackle, pop of your morning Rice Krispies,” he said. “It sounded neat to me, but it must really give regular homeowners the willies.

“I mean, the idea is that, underneath the bark of their back yard trees, are tens of thousands of these creatures, eating, eating and eating. The sound you hear is their little mandibles clicking together as they go about their meal.”

Forget the maddening Medfly or the African killer bees. Walt Ekard gets the shivers just thinking about the borer beetles. And the sound of the chain saws biting into yet another sick tree.

“They’re fierce-looking,” he said, describing the unique black and yellow design on the beetles’ back. “They’re bad. They’re a lot bigger than the wasps we’re sending in to control them.”

Rancho Santa Fe’s campaign against the longhorned borers began four years ago when resident Chuck Charman noticed that a handful of the 250 eucalyptus trees on his property were under some kind of attack.

“One day it was green,” he said of one of the afflicted trees, “and three days later it was brown. Then, after another week, all the bark had fallen off. When I cut one of the trees down, I noticed all the beetle canals.”

Charman, a 48-year-old engineer at General Atomics, contacted the scientists at UC Riverside, who just then were beginning the project to locate natural enemies of the beetle back in Australia and then try to breed them here.

Charman sent flyers to other ranch residents and kept in touch with the researchers, waiting for them to complete the laborious wasp quarantine and breeding process.

Then, recently, during one of his routine calls to Riverside, Charman learned that government funding for the program had been discontinued.

“I told them maybe there was something we can do.”

He brought the idea to the Rancho Santa Fe Assn. board, which earlier this month voted to begin funding the project. Along with a $50,000 contribution from Caltrans, the researchers are counting on other communities like Rancho Santa Fe to do their part.

“The problem is that the eucalyptus isn’t as high-profile as some other fruit-bearing trees, so the state doesn’t care about it,” Hanks said. “They see it as a homeowner’s problem. But, in places like Rancho Santa Fe, with 100,000 of the trees that are important to their sense of identity, it’s an important consideration.”

Few ranch residents could imagine their community without the eucalyptus, about 3 million of which were first planted in the area in the early 1900s by the Santa Fe Railway--with the plan of using them as railroad ties.

It was soon discovered that the locally grown trees were too brittle and cracked when the railroad spokes were driven in. The rest, locals say, is history. The railroad sold the land to establish California’s first planned residential community.

“Today, the eucalyptus is part and parcel with the identity of the Ranch,” Ekard said. “We use the trees as a symbol in the insignia that goes on all our official stationary. It’s hard to imagine Rancho Santa Fe without eucalyptus trees.”

If the UC Riverside program works, no one will have to. Sometime in the coming months, the researchers plan to loose possibly 50 pairs of the wasps throughout the ranch--returning frequently to test whether the wasps are indeed stemming the development of the beetle and whether they are reproducing adequately in the wild, Hanks said.

“If all goes well, we might see a difference by next spring,” Hanks said. “Meanwhile, people probably won’t even notice the wasp are here--unless, of course, they sat on one and got stung. They’re not gregarious like the yellow jacket. They’ll spend most of their time around the eucalyptus trees.”

Meanwhile, Rancho Santa Fe residents like Chuck Charman will keep their collective fingers crossed that the mighty eucalyptus will eventually shake off the beetle plague with a little help from some insect friends.

“I don’t know, the eucalyptus tree has become sort of the heart and soul of this community,” he said. “Without them, this would be a far less beautiful place.”