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Scientists Muster Army to Combat Beetles Threatening Southland's Eucalyptus Trees : BYNANCY RAY

October 11, 1987|Times Staff Writer

SAN DIEGO — Bob Dingeman, supervisor of the Scripps Ranch Maintenance District and holder of almost every other civic post in the community at one time or another, knows more than most how dearly local residents hold their 35,000 or so eucalyptus trees.

"People here are proud of their community and proud of our trees. That's how they think of the eucalyptus. It's what makes this a unique community," Dingeman said. "It's like cutting off your arm to cut down one of our trees."

That's why Dingeman and many others are more than a little concerned about an infestation of the longhorn borer beetle. It is killing eucalyptus trees not only in Scripps Ranch, but throughout Southern California. The beetle was first found in Orange County's El Toro area about three years ago.

The beetle infestation at Scripps Ranch was discovered two years ago, and since then about 200 trees have been found to be diseased and cut down. They are either burned or taken to the Miramar landfill, where the wood is reduced to chips so small they can't harbor beetle eggs or larvae.

Although new trees are planted to replace those cut down, it just isn't the same, Dingeman says. Most of the trees in Scripps Ranch have been there for decades, long before they were surrounded by houses. As for the new homeowners, who feel that the eucalyptus groves set them apart from newer, treeless subdivisions, they can't help but wince when they hear chain saws biting into yet another sick tree.

But now help may be on the way, specifically from Down Under.

University of California, Riverside, entomologists, armed with parasites and predators imported from Australia, are about to launch an all-out attack on the longhorn borer beetle.

Help Is Coming

The help is coming none too soon, as the beetle infestation has now spread southward from Camp Pendleton to Lemon Grove--hitting stately stands of eucalyptus in Carlsbad, Rancho Santa Fe, Balboa Park and Scripps Ranch.

Unlike a pest such as the Mediterranean fruit fly, which poses a grave economic threat to California agriculture, the longhorn borer beetle is primarily an aesthetic menace. That's because it only attacks eucalyptus trees, which have limited commercial value.

San Diego County agricultural officials haven't been overly worried about the infestation, given their priority of protecting commercial crops. "Of course, we are concerned, but there is nothing we can do," said George Opel, the county's veteran bug-hunter.

Spraying is ineffective against the winged beetle, and it has no natural enemies in the United States, Opel said. As a result, the county's agricultural staff has had to be satisfied with distributing pamphlets warning against spread of the pest in freshly cut eucalyptus wood.

Now, however, new weapons--some with teeth--are poised to enter the fray.

The UC Riverside entomologists traveled to Australia recently and returned with natural enemies of the eucalyptus-attacking beetles in the form of both predators and parasites, and the scientists now are growing sufficient quantities of the beetle destroyers to launch an all-out attack on the pest.

The entomologists were not reachable for comment, but it looks as though the posh estate community of Rancho Santa Fe may be one of the first test sites for the beetle battle.

George Parrish, manager of the Rancho Santa Fe Assn., said, "Things have calmed down a bit since last year," when some trees on the golf course and along Rancho roads were found to be infested with borer beetle larvae. About a dozen trees were cut down on association property.

Uncounted others were identified on private property and removed by the property owners, he said.

"We know that the problem has not been eliminated," Parrish said. "The beetles are still here, and there is nothing we can do about them."

A major part of the problem is that it is difficult to identify infested trees until the beetle larvae have done their dirty work and the tree is dying.

Bob Maheu, until recently, was in charge of maintenance in Rancho Santa Fe. He visited the community earlier this week after the hot Santa Ana had waned. He said he noticed a number of trees with discolored and wilting leaves, a sure sign of stress.

When the trees are in such condition, they make a prime habitat for a beetle infestation.

Maheu explained that eucalyptus becomes stressed when there are high temperatures and little water.

The beetles apparently sense the vulnerability of the tree and lay their eggs in its bark. When larva hatch, they bore into the tree trunk, restricting further the movement of sap and water to the limbs and hastening the tree's death.

Healthy Trees Resistant

Young, healthy trees and those receiving adequate water are usually avoided by egg-laying beetles, Maheu said. Healthy trees can fight off the beetle larvae by exuding sap that drowns the borers.

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