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War of the Whitefly : Strategies: Scientists uncork their biological weapon against a pest infestation. They’re pitting tiny wasps against tiny flies.

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TIMES STAFF WRITER

Scientists launched the first attack in a biological war against the ash whitefly Friday when they placed 60 tiny parasitic wasps in a San Fernando Valley park.

Perched atop ladders in Encino’s Balboa Sports Center, researchers reached into nylon mesh bags that had been wrapped around branches of two infested trees and uncorked several narrow, inch-long vials containing the predators.

“We’ve just taken a small step on a long journey,” said Los Angeles County Agricultural Commissioner Leon Spaugy.

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Scientists are hoping for marked progress by 1991 but say it will take up to five years to bring the whitefly under control.

The gold and black wasps, imported from Israel, look like dust specks and are about half the size of a pinhead. They do not sting humans and can only multiply by laying their eggs within immature whiteflies. As the eggs develop, the growing wasps consume their host from the inside out, said Larry Bezark, a pest management specialist with the California Department of Food and Agriculture.

The whitefly has invaded trees from the Mexican border to Sacramento since it was first discovered at a Van Nuys fruit stand 14 months ago. Researchers fear the pest, accidentally imported from Europe or the Middle East, could spread through most of the state by next year because it has no natural enemies here.

“This is very serious,” UC Riverside entomologist Tom Bellows said as he stood beneath a tree infested with tens of thousands of whiteflies. “This is one of the most serious infestations of a foreign insect in the last 10 years.”

Friday’s controlled release, coordinated by scientists at the University of California, Riverside, and the California Department of Food and Agriculture, is the first in a series of such test releases planned this month in Los Angeles, Orange, Riverside, San Bernardino and San Diego counties.

The wasps will breed inside the mesh bags, enabling scientists to monitor their progress. In all, 300 of the wasps will be deployed in the bags this fall, with as many as 10,000 or more scheduled for similar tests in the spring of 1990.

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The test releases will help scientists determine if the wasp can survive the California winter outside the laboratory. Researchers are optimistic, noting that the wasps thrive under similar climatic conditions elsewhere. Entomologists also will be testing wasps imported from Italy, where the whitefly is kept under control by natural conditions.

The white-winged pest sucks vital juices from leaves, weakening and eventually defoliating trees. Ash and pear trees are its most common victims, but loquat, pomegranate, citrus, toyon and others are also at risk.

Pesticides have been unsuccessful for several reasons. Chemicals have a difficult time penetrating the waxy coat of the whitefly, and their eggs are difficult to reach because they are laid on the underside of leaves, Bellows said. Also, the sheer number of whiteflies, which Bellows estimated in the billions in the Los Angeles basin, make the use of pesticides impractical and undesirable.

“There is no reason to attempt that approach when there is such a good, environmentally sound alternative,” Bellows said.

Although damage so far has primarily been confined to shade trees and back-yard fruit trees, officials warn that the non-native pest poses a severe threat to the state’s nursery and citrus industries. “There is a great potential for loss,” Bellows said.

In parts of Europe where the whitefly has gained a foothold, up to half the pear and apple crop has been destroyed, he said. “But we’ll beat it before it happens here.”

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Since the whitefly sucks more juice from plants than it can use, it leaves a sticky ooze in its wake that discolors fruit, stains patio furniture and ruins automobile paint. Residents throughout the basin have complained that the swarming pests, which stick to hair and clothing, have ruined back-yard barbecues, driving traditional outdoor activities inside.

The biological control program, funded by government agencies, grower groups and the University of California, has cost less than $100,000 so far, Spaugy said. But Bellows estimates the biological control program will cost $120,000 a year for up to six years.

State Assemblyman Terry Friedman (D-Tarzana) said Friday that he will introduce an urgency measure when the Legislature reconvenes in January that will provide $2 million over the next five years to combat the whitefly in California.

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