Wasps to Be Introduced to Save Trees

Using insects to fight insects, officials are scheduled today to release tiny Australian wasps at Valley Village Park to attack the red gum lerp psyllids that are plaguing eucalyptus trees.

It will be the first use of the wasps to combat the psyllids in the United States, said Gilda Franklin, spokeswoman for the Los Angeles Department of Recreation and Parks, which is coordinating the attack.

Researchers have been studying the wasps since last August to make sure their introduction here will not pose other environmental hazards, she said.

The insects do not sting people or harm beneficial psyllids, which are tiny flying bugs that suck sap from foliage.

UC Berkeley professor Donald Dahlsten, leading researcher on the problem, will release 100 males and 100 females about the size of a comma.

With a name thousands of times bigger than the insect--Psyllaephagus bliteus--the tiny wasps have been bred through several generations while in quarantine at the university’s College of Natural Resources Center for Biological Control.

The lerp psyllids, which also originated in Australia where eucalyptus trees are native, were first discovered in El Monte in 1998 and are now widespread throughout the state. The infestation at Valley Village Park, one of the worst in the city, was brought to the attention of city officials a year ago after a resident, Patricia O’Connell, contacted The Times.

The bugs have since stripped trees of foliage in many areas, including along Chandler Boulevard, where some of the trees appear dead.

“All of the trees are suffering and are very sick looking,” said O’Connell, who takes daily walks through her neighborhood and the park. “I am afraid we are going to lose them.”

Dahlsten and his research assistants were en route to Los Angeles on Tuesday and could not be reached for comment. However, his Internet Web site warned that the lerp psyllid attacks “may stress trees and make them susceptible to fatal attack by other insects.”

During a recent sampling field trip, the site reports, “Dahlsten confirmed the death of some red gums in the Los Angeles area, with lerp psyllid damage being the suspected cause.”

Weakened trees can be attacked by borers, for instance, which can kill them. A 125-year-old eucalyptus tree in Tustin had to be felled in April.

In earlier interviews, Dahlsten said extensive tests were required before releasing the wasps to determine if they could provide a permanent solution to control the psyllid population.

The city last year released millions of ladybugs in Valley Village Park and elsewhere in an effort to control the infestation. The ladybugs are among natural predators that eat psyllids, as well as aphids and other small insects. But in areas where the infestations are being monitored, the addition of ladybugs has not effectively countered the psyllid invasion, officials said.

The psyllid, a small flying insect that feeds on plant juices, has been collected on 27 species of eucalyptus in California, but is causing the greatest damage to the red gum variety, a common ornamental tree, according to Dahlsten.

“These are tough trees,” Dahlsten said in an earlier interview, “but the question is how many times can they be defoliated before they die?”

The insect produces large amounts of honeydew, which results in blackened foliage because of a fungus called sooty mold. The honeydew also creates a sticky mess on whatever it lands on.

The imported wasp kills a psyllid by stinging it and laying an egg inside. The wasp larva then feeds on the host until it matures and repeats the cycle, researchers said.