A Fresh Foe in the Eucalyptus War

The seven-year war against a sap-sucking insect that has ravaged eucalyptus trees in California has shifted to one of its cousins, the lemon gum psyllid, which forced Placentia this week to cut down more than 65 trees.

Its predecessor, the more virulent red gum lerp psyllid, seems to have had its ranks diminished, according to public-works and tree experts, but not before killing thousands of trees from San Clemente to Sacramento since it arrived from Australia in 1998. The infestation’s front line was in Lake Forest, where the insect laid waste to its signature eucalyptus groves.

Psyllid-eating wasps, ladybugs, pesticides and frequent watering were credited with slowing the earlier outbreak.

“The wasps seem to be working, but it’s been a combination of things,” said Teresa Proscewicz, a spokeswoman for the Los Angeles Department of Recreation and Parks.

The department, Proscewicz said, has spent more than $500,000 combating the psyllid after it damaged 30,000 eucalyptuses, killing an estimated 20,000 trees on public land.

She said Los Angeles had to remove 1,500 eucalyptus trees near park sidewalks and trails, where weakened branches could have fallen and injured people. Budget restrictions prevented cutting and removing dead trees on hillsides not frequented by the public.

On Wednesday, Placentia cut down trees with weakened limbs that could fall onto Bastanchury Road, a city spokesman said. The cost was $30,000, including replanting.

The psyllid attacks the eucalyptus by draining fluid from the long, finger-like leaves, laying eggs and covering them with a sticky, white tent-like structure known as the lerp. On any given leaf, there can be 20 or 30 lerps.

Though the newcomer isn’t as bad, it still sucks the sap from tree leaves, which may stress the trees, making them susceptible to fatal attack by other insects, said Timothy D. Paine, a professor of entomology at UC Riverside.

“We don’t have enough experience with the lemon gum psyllid,” Paine said. “But based on what we’ve seen in the last couple of years, it probably won’t be as bad” as its deadlier cousin.

There are about 600 species of eucalyptus, nearly all originating in Australia. California has about 90 species.

The first eucalyptus trees appeared in California in the mid-1800s when entrepreneurs envisioned them as a good source for railroad ties, landscaping and construction material. But the wood proved too brittle and prone to cracking.

They enjoyed a relatively pest-free existence until 1985, Paine said.

Since then, a series of bugs -- wood-boring beetles, tortoise beetles and lerp psyllids -- has plagued them. The most recent psyllid infestation was discovered in August 2000 at Disneyland Resort and surrounding areas of Anaheim, experts said. Since then the insect has been spotted in Placentia and Lakewood. Paine also said two psyllid varieties had been discovered cohabiting.

They live together on the leaves of two species of eucalyptus, the lemon-scented gum and spotted gum. But it is unknown why they have taken to living together, Paine said.

“What is going on is the big question,” he said. “We didn’t have any pests on eucalyptus up to 1985. Now we’re seeing the introduction of new pests at one a year. We now have up to 18 psyllids, leaf beetles and wood beetles.”

He said the pests’ destructive effects had been diminished because many homeowners were watering their eucalyptus trees more frequently.

The lemon-scented and spotted gum trees’ smooth, white bark and graceful branches make them a favorite among landscape architects, Paine said.

In Lake Forest, homeowners conquered the infestation with insecticides and psyllid-eating wasps imported from Australia.

“I think we’ve won the war,” said Laurie Smith, chairwoman of the Lake Forest Community Assn.’s tree committee.

Smith credited the wasps and a drive to urge homeowners to water trees heavily.

“We’re not getting that destructive defoliation anymore, and we’re not losing trees,” she said.

Smith said they cut 5,800 eucalyptus trees. With help from the state forestry department, the nonprofit Shadetree Partnership and volunteers, they have replanted 1,280 new trees.

But Lake Forest officials and maintenance staff are not ready to declare victory.

“We’re at a truce,” said Phil Liso, a landscape inspector.