Tiny Ash Whitefly Lays Siege to Trees, Tempers

Nick Nisson used to stand outside and admire the ash and pear trees towering over his Tustin home.

These days, though, the 32-year-old entomologist views his beloved trees with a look of concern. Swirling white clouds of flies the size of a pin head have invaded virtually every leaf of the two ash trees and the ornamental pear tree, which tower 35 feet above his sprawling front and back yards.

“You see ‘em in the air, and if you’re directly under the trees you really notice ‘em,” he said. “The leaves that fall are stuck with the honey they produce. The trees look messy and dirty.”

Nisson’s job with the Orange County agricultural commissioner’s office makes him well-acquainted with the source of his infestation problem: ash whiteflies, millions of them.

In the final days of summer, the wrath of the ash whitefly, a pest without enemies, reached an explosive crescendo throughout Southern California, attacking millions of trees and prompting an unprecedented outcry from fly-tormented homeowners.

From Buena Park to Tustin and throughout most of Los Angeles, Riverside and San Bernardino counties, thousands upon thousands of residents who have long found cool comfort beneath their shade trees are under siege by what is perhaps the most menacing insect to have swept into residential neighborhoods, agricultural officials said.

Barbecues have been canceled or ruined. Patio furniture has stayed in the garage. Housework has doubled. Many residents have purchased car covers and others keep a bucket of cleaning solution on hand to wipe flies and their sticky droppings off windshields.

Windows stay closed. The insects stick to hair like dandruff. Simply chatting outside with a neighbor is an arm-flailing exercise.

“We’ve never had anything that comes close to matching the citizen-based outcry over this,” said Bob Atkins, Los Angeles County deputy agricultural commissioner for pest prevention.

In Orange County, Nisson said, the agricultural commissioner’s office receives up to 100 calls a day from homeowners and nurserymen besieged by the flies. There have been so many complaints that officials recently installed a tape recording that offers a brief history of the ubiquitous fly and what to do about it.

Not that there is much to do, however.

Nisson’s advice: “Live with it. Admire its ability to reproduce so fast, spread so quick.”

“They are everywhere. Everywhere!” said Lynn Olson of Glendora, whose front and back yard trees are teeming with flies. “Some days I feel like taking an ax to every tree on the block. It’s so frustrating.”

In the last several weeks, Atkins said his office has received up to 200 calls a day from fly-tormented homeowners. Throughout Los Angeles county, local city officials say they too are receiving scores of calls.

But there is no good news for callers.

Virtually nothing can stop the flies, entomologists said.

They multiply with lightning speed and have wax-coated wings that are almost immune to pesticide sprays. Residents who do spray find only a few hours respite from the swarms and inadvertently kill insects that can be beneficial to gardens.

Others have turned to drilling holes in their trees and inserting intravenous capsules that leach pesticides in the hope that lethal doses will eventually flow far enough to kill the leaf-sucking flies. Agriculture officials discourage the practice because it is only a temporary fly killer and repeated boring kills trees.

As a last resort, some residents are screwing high-pressure nozzles on their garden hoses and shooting water on their infested trees in an attempt to blast away the pests.

A “forceful water spray” can ease the infestation, but pesticides don’t work, Nisson said. When the small flies are doused with pesticides, they “repopulate quickly. . . . So we don’t like to recommend spraying. You’re putting pesticides into the environment, and you’re not getting results back. You’re better off not using it.”

The flies attack a wide variety of trees, attaching themselves like white crusts and laying eggs on the undersides of leaves. The flies are slowly sucking the life out of two of the region’s most popular shade trees--ash and ornamental pear.

But they also have an appetite for others, including loquat, pomegranate, Christmas berry, peach and plum. They will also latch onto citrus, but it is not a primary “host tree,” agriculture officials said.

Infested trees will “live under stress” for several years before dying.

The flies, which were first detected in July, 1988, by a Van Nuys vegetable-stand owner, have no natural predators in Southern California, the first North American region to host the fly. The insect is a native of Europe and the Middle East.

The first Orange County sighting came in October, 1988, when an Anaheim homeowner found the pest in his back yard. Orange County agriculture officials confirmed its presence again last February when a Buena Park nurseryman found the bugs on his stock.

Native Lands

But by the time the ash whitefly was identified by state entomologists, it had spread throughout Los Angeles County, free from European species of wasps and ladybugs that control the flies in their native lands.

In Orange County, officials who conducted a survey this June found “very, very light” infestation in central and South County. But by late August, “that completely changed” and the flies were “everywhere,” Nisson said.

Agriculture officials say the main hope for ash whitefly control is to import the enemy insects. This week, a state entomologist who is in Italy sent back two boxes of the stingerless wasps and ladybugs to UC Riverside, where the insects will be studied.

If the predators can survive and breed in Southern California, feed off the whitefly and not become destructive pests themselves, they could be turned on the ash whitefly as early as next spring, said Thomas Bellows, UC Riverside associate professor of entomology and the whitefly expert supervising the study.

Then, it would take anywhere from two to eight years before residents will detect any kind of population reduction, agriculture officials said.

This morning in Anaheim, officials from the California Agricultural Commissioners and Sealers Assn. are meeting to discuss those biological controls.

Early predictions of devastating effects on the state’s $831-million-a-year nursery industry have not come to pass, state agricultural officials and several large growers said. The infestation has not struck the mammoth $634-million citrus industry either.

Still Orange County agriculture officials said some nurseries that ship stock out of state have found their plants rejected. Inspectors in Arizona, Florida and some other states will not allow stock infested with whiteflies to be exported, Nisson said.

So far, the flies have been mainly attracted to big, healthy trees growing along residential streets and shading the back yards of homeowners.

Infested trees rain droplets of a molasses-like substance--the ultimate insult, fly excrement. When the flies swarm, the excretion floats through the air and settles like sticky dew. Dead, sticky leaves turn moldy and drop onto the sticky ground. The sweet substance attracts ants.

In Whittier, Sylvia Ochoa, 34, said a recent back yard gathering was ruined when flies began swirling around her guests. First, her friends thought the nearby hills were on fire because so much ash was floating in the air.

No, Ochoa told them, it was the ash whitefly.

Stuck to Hair

“Then for some reason the flies were attracted to the ladies with hair spray,” Ochoa said. “It was kind of funny, they all left with white flies stuck to their hair.”

In Van Nuys, gardening enthusiast Carol Mueller, who now wears two bandannas to protect her hair and ears against the swarms, echoed the wishes of many who have found themselves under ash whitefly siege.

“I’m hoping for a cold, wet winter,” she said. “Maybe that will take care of the little devils.”

Times staff writers Jim Carlton and Lanie Jones in Orange County contributed to this story.