EUCALYPTUS TREES UNDER BUG ATTACK.

Byline: Michael Coit Staff Writer

As city crews set traps in San Fernando Valley eucalyptus trees to capture a destructive pest, a Berkeley entomologist is racing toward a cure for the infestation.

The red gum lerp psyllid so far has faced few enemies in its spread across Southern California and the Bay Area since being discovered in June last year - the worst tree infestation since the ash whitefly a decade ago.

While trapping reveals the unyielding infestation's depth, Don Dahlsten thinks he has found a predator for the Australian import.

Dahlsten, a master in the art of biological pest control, recently returned from Down Under with a palette of four parasitic wasps. Finding one that preys on the psyllid would be Dahlsten's next masterpiece, but he won't have time to appreciate the work.

With the aphid-like pests infesting a half-dozen eucalyptus varieties, stressing trees in the midst of the state's dry season, Dahlsten hopes for a spring release of wasps across the state.

``There are so many problems in this business that I don't like to make any promises,'' said Dahlsten, who found a wasp to prey on blue gum psyllids in the early 1990s.

``If the wasp behaves like the wasp we released for the blue gum psyllid, it will reproduce across the state,'' he explained. ``But I need to make sure I am releasing something that is not going to cause yet more damage.''

Dahlsten is working against a backdrop of great public anticipation.

Despite reassurances from public agencies that eucalyptuses should be hearty enough to endure the infestation, residents with affected trees in yards and street parkways fear the trees won't survive.

The eucalyptuses are suffering severe defoliation that leaves them vulnerable to wood-boring pests.

Piles of leaves

More than 30 eucalyptuses lining a hillside behind Lora Rosene's home in Sylmar are nearly devoid of leaves.

``In our yard we get big piles of the leaves every day,'' Rosene said. ``They look like they're dying. I feel bad. They're beautiful trees.''

Rosene said the loss of leaves has more than an aesthetic impact. ``They're pretty and they help cut down the noise from the freeway.''

Judy Baumbach noticed the stand of eucalyptuses along her Woodland Hills street were in trouble when so many leaves fell that the trees provided little shade this summer.

``Imagine what this street would look like without those trees. It would be naked,'' she said. ``So you can see why we're protective of our trees.''

Her fears eased somewhat after talking with the Los Angeles street tree crew collecting and replacing traps in the trees. They explained the efforts to eventually control the eucalyptus pest.

``It's reassuring that something's being done. Only time will tell,'' Baumbach said.

The psyllid infestation has been the worst on street trees since a whitefly descended on ash trees across Los Angeles in 1989. The ash whitefly was finally controlled three years later after parasitic wasps were introduced from Israel and Italy, said Rosser Garrison, entomologist for the Los Angeles County Agricultural Commissioner's Office.

Public outcry

Ash and eucalyptus trees are not on the economic scale of fruit and nut trees that draw intensive eradication efforts when a few pests turn up in traps. Still, the potential losses generated enough public outcry for county agricultural officials to consider the pests as a threat, Garrison explained.

``Once these things get here, some of the stuff is a blip on the radar screen and nobody notices it,'' he said. ``This has been something that does impact much of our public.''

About six new agricultural pests are identified in California each year.

Like fruit flies, the red gum lerp psyllid probably arrived on some plant or cargo material transported illegally around federal and state inspection efforts, Garrison said.

Given the spread of this and other psyllids, the pest is here to stay, entomologists said.

Their adaptability parallels the many varieties of eucalyptus found across the state, which are native to Australia.

Consider the spread of psyllids at the Los Angeles Zoo. They are feeding on the same leaves and young shoots favored by koalas, the more likable Australian import.

``The danger will be if defoliation causes additional stress,'' said Teresa Poscewicz, the zoo's horticulture manager. ``We're trying not to change maintenance practices, because if you've been maintaining them for a long time that will cause additional stress, and the trees will be more prone to another insect infestation that may cause the death of the trees.''

There is little for zoo officials to do other than forage for koala food in other areas of the city.

Pickings, though, can get slim.

The depth of the local infestation is revealed in the dozens of petri dish traps collected weekly from trees in Valley neighborhoods and parks, as well as at the zoo. The traps are covered with the tiny, slender green psyllids captured when they land on a sticky substance.

Valley areas were selected because the region is among the most heavily infested. The Valley has the greatest spread of the city's 20,000 eucalyptuses, particularly the red gum.

Ladybugs and lacewings also can be seen on branches and leaves. They eat a share of psyllids but are indiscriminate feeders who can't control the infestation, said Leroy Castellano, a certified pest adviser doing trapping for the city of Los Angeles Public Works Department.

``They do what they can. But there are millions and millions of psyllids,'' Castellano said, looking over 10 traps collected from a stand of red gum eucalyptuses in Woodland Hills. ``That's why we need the wasp.''

Parasitic wasps are workhorses of biological pest control - the science of raising good bugs to control bad bugs.

Biological pest control was born in California in 1889 when the Vedalia ladybird beetle and cryptochetum fly were introduced to prey on the cottony cushion scale, a citrus pest, entomologists said.

Toiling since 1963

Dahlsten has been toiling in the field since 1963, identifying, culling, breeding and releasing good bugs to deal with a variety of urban street tree insect problems. He is a professor at the Center for Biological Control in the College of Natural Resources at the University of California at Berkeley.

``I like metropolitan areas, because if we can solve the large problems, then the smaller cities are a piece of cake,'' he said.

Agencies responsible for trees across Los Angeles County brought Dahlsten in to help solve the psyllid problem in July.

Dahlsten was in Australia by the middle of August, collecting parasitic wasps that feed on red gum lerp psyllid. The areas were identified by colleagues at Australian universities.

Because the wasps and psyllids are in balance, Dahlsten needed several weeks to collect about 200 wasps. He brought them back in quarantine under permits issued by the U.S. Department of Agriculture and the California Department of Food and Agriculture.

``That hurdle is over. The question is, did we get the right parasite,'' he said.

The wasp lays its eggs in the white cone that the psyllid nymphs create. When the baby wasp hatches, it feeds on the nymph.

In the field in Australia, Dahlsten lifted lerps in search of dead psyllids with living parasites inside. ``It looks like a mummy - a petrified psyllid, if you will.''

As they emerge, Dahlsten will look for wasps that prey specifically on the psyllid and raise them in an insectery. Because he has identified four different wasps, Dahlsten must be careful not to breed ``hyperparasites'' that feed on the primary psyllid parasite.

``I can't just say here's a wasp that looks good and let it go. I don't want to hurt something else,'' he said.

Dahlsten is hopeful, having successfully battled the blue gum psyllid to a truce with a parasitic wasp in the state's southern and central coast counties, including Los Angeles County.

But Dahlsten said there is one difference between the blue gum and red gum psyllid.

``There was only one parasite species, and it was very clear (with the blue gum),'' he said. ``With this we know we have at least four species.

``We don't know what the game is.''

CAPTION(S):

3 Photos, Box

Photo: (1--Color) no caption (Eucalyptus pest)

(2--Color) City tree surgeon Taketo Kobayishi heads up into the eucalyptus branches to change a psyllid trap.

(3--Color) Psyllids stick to a trap that was hanging from a eucalyptus tree.

Michael Owen Baker/Staff Photographer

Box: THE EUCALYPTUS PEST