State Alters Strategy in Medfly War : Eradication: Agriculture officials are about to replace aerial malathion spraying with the release of millions of sterile flies in northern Orange County and around Los Angeles.

Nori Tanaka, a scruffy, gray-haired entomologist, trudges through a converted tuna-packing shed, flicking flies off his face. It is just before the dawn of another humid day. In one corner of the ramshackle building, workers grind out sticky, brown fly food in a cement mixer. In another, fly pupae are sifted through a makeshift device of cardboard, old broom heads and wire mesh.

Tanaka reeks mightily of sugar, yeast and other odors that come with the job of mating insects. A cloud of flies surrounds his face. He gazes about the shed, proudly surveying the noisy scene. A few flies float in his coffee cup. He drinks it anyway.

“It takes a certain man,” Tanaka says, “to be a rearing man. You have to dream this stuff.”

Tanaka is the country’s foremost fly “rearing man.” His domain is the California-Hawaii Agriculture Medfly Project--a facility that throughout this summer will be the most important outpost in the state’s war against the Medfly in Southern California.

Agriculture officials are about to attempt a tactical shift in their effort to eradicate the Medfly, replacing aerial malathion spraying with the release of millions of sterile flies in northern Orange County and around Los Angeles. If all goes well, and if no fertile flies are found by the end of next month--a major qualifier--the sterile fly releases will replace the controversial pesticide program over all but about 10% of the large infestation area.

Devised 40 years ago, the simple concept calls for the release of millions of sterile Medflies in successive waves. The steriles, made so by exposure to radiation, are intended to numerically overwhelm their sexual competitors in mating with wild flies. With no offspring from the mating, the wild flies eventually will die out. Or so the theory goes.

Largely undetectable by the public, harmless to the environment and, as far as anyone can tell, harmless to people as well, the sterile Medfly approach not only will eradicate the pest, agricultural officials believe, but will also end the public outcry over pesticide spraying.

Much of the task hinges on Tanaka, who as operator of two of the three major sterile breeding facilities here must be able to deliver the irradiated flies in sufficient numbers to support the campaign. It is a difficult challenge; shortages of sterile flies, coupled with a rash of Medfly discoveries over the last few months, already forced the state to retreat from its original May 9 deadline to end spraying.

There are other hazards. Improperly sterilized flies can be explosively dangerous to the eradication campaign; some officials still maintain that this occurred with a batch of South American flies brought in to battle the 1981 infestation. There have also been complaints from residents that the clouds of sterilized flies have an uncanny knack for knocking into freshly painted walls.

And the central question--do the sterile releases work?--remains less than resolved in scientific circles. No scientist can explain precisely how the approach works, nor can they say with certainty if it will succeed on the scale to be attempted in Southern California.

“There’s a lot we don’t know,” Tanaka said in an interview last month. “I believe it works, but there have been so many failures, too.”

Tanaka, who has been rearing flies for four decades, is considered the dean of sterile Medfly production. Most of the techniques and equipment used in the United States for raising Medflies were developed by Tanaka, a born tinkerer who constantly prowls the facilities in a grimy T-shirt, checking on food mixtures or adjusting the temperature in the rearing rooms.

Since the beginning of the year, he has spent almost every waking hour inside the tuna shed, located in an industrial section of Honolulu, breeding the millions of flies demanded by California.

“This is the only thing I know,” he said. “It’s my whole life.”

The state’s new battle plan is actually a return to a strategy that agriculture officials originally intended to use last summer, before the Medfly outbreaks exploded throughout the Southland.

When the first Medfly infestation was detected last July 20 in Elysian Park, officials believed that the outbreak was an isolated case and could be quietly eradicated with one or two aerial spraying followed by the release of sterile flies.

But by December, the Medfly had spread through 200 square miles of Los Angeles and Orange counties and state officials admitted that had exhausted their supply of sterile Medflies. Their only alternative was to spray wide sectors of Southern California with repeated aerial doses of malathion, deploying steriles in only a few pockets of infestation.

For the last four months, the state has pushed to increase sterile fly production and is now receiving about 300 million sterile flies a week--enough to treat about 300 square miles of the infestation.

In Orange County, the sterile releases are to be limited to an eight-square-mile area of North County that includes parts of Brea, La Habra and Fullerton. Hit nine times by malathion spraying in the last six months, that area is scheduled for the release of hundreds of millions of sterile flies over coming months. The releases started last week.

About 400,000 residents in the county’s larger Medfly zone--a 36-square-mile zone centered in Garden Grove--will continue to face spraying. Faced with a potential shortage of sterile flies, state officials decided to treat Garden Grove with three more malathion applications--tonight, May 23 and May 30.

Tanaka’s two breeding facilities turn out a weekly supply of about 150 million sterile Medflies. Another 120 million are arriving from a breeding facility in Mexico, along with about 40 million from a third rearing facility in Hawaii. The flies are raised in places where the pest is already established.

The process begins in the breeding facilities where the flies are raised, dyed (to make sure they are not confused with wild flies), sterilized by exposure to radiation, and then shipped to California in long, sausage-like bags that each contain thousands of fly pupae.

The adult flies emerge after arrival and are then scattered by truck or airplane throughout an infestation zone at a rate of about 1 million every square mile every week. Prior to the introduction of steriles, an infested area usually is sprayed once or twice with malathion to reduce the wild fly population.

The flies are released for three generations--about three or four months during the summer.

It’s a virtually benign treatment that seems to make scientific sense, although the record has been less than perfect.

“There’s no reason why it can’t eradicate an insect,” said Edward F. Knipling, the now-retired originator of the idea. “I don’t know how you can miss.”

Knipling was a junior entomologist with the U.S. Department of Agriculture when he hatched the idea of using sterile insects as a weapon of eradication in the 1930s. At the time, much of the southern United States was infested with a pest called the screw-worm fly, whose burrowing larvae killed livestock.

His colleague jeered the idea. Knipling himself thought of it as a “long shot.”

It took nearly 15 years before Knipling heard of a way to sterilize flies using radiation. The series of eradication programs he eventually launched cleansed the United States and Mexico of the screw-worm pest. The program still continues today and is now poised to push through Central America.

Not all such eradication programs have been as successful. Consider the massive Northern California Medlfy infestation in 1980-82, which some officials and scientists contend was spread through hundreds of square miles by the release of sterile flies from Peru that may have been improperly sterilized.

Some scientists say generally that California has never had much luck in using sterile techniques against the Medfly. James R. Carey, a UC Davis entomologist and one of five scientific advisers in the state’s eradication campaign, said sterile Medflies have been released in this state eight out of the last 15 years and yet infestations continue to crop up, sometimes in the same place over and over again.

Carey and other scientists agree that the technique has succeeded each time in substantially reducing the Medfly population but, they ask, did it wipe out every last vestige of the pest?

“It’s a very good tool for suppression of a population. The evidence of that is clear,” said Ronald Prokopy, an entomologist at the University of Massachusetts and an expert on the Medfly. “But eradication, that is a different story. I have no idea.”

Little is known about how the technique actually works. For example, scientists are not certain about such fundamental questions as whether it is the sterile male flies, sterile females, or both, that break the reproduction cycle.

Prokopy, who was chairman of the state’s science advisory panel in the eradication of the apple maggot in the early 1980s, said scientists have only begun to understand how sterile flies act in the wild. What they have seen is not entirely encouraging.

To begin with, he said, the sterile flies appear to be less competitive than wild flies, partly because the sterilization process itself slightly weakens them. On top of that, Prokopy said, the artificial environment of the breeding labs seems to produce domesticated weaklings.

“They’re different, that’s a fact,” Prokopy said. “They haven’t forgotten how to do things, they just don’t do them as well. It’s like chickens, you put them in the wild and they’ll get eaten.”

Kenneth Kaneshiro, director of the Hawaiian Evolutionary Biology Program at the University of Hawaii and a Medfly expert, agreed, saying that flies fall into two general categories: duds and studs. Sterile flies are generally duds.

In the wild, he said, lab-reared flies are lousy at performing their species’ complex mating rituals, are not good at defending their territory, and they are downright miserable at finding mates. “Sexually inadequate,” Kaneshiro said.

The qualities of sterile flies aside, there are constant problems in rearing them in the huge quantities needed for an eradication program.

When state Department of Food and Agriculture Director Henry J. Voss announced in March his decision to replace spraying with sterile fly releases, a key to his plan was receiving millions of flies from a just-completed U.S. Department of Agriculture facility in Waimanalo, Hawaii.

The $7-million Waimanalo facility, the one Hawaiian facility not run by Tanaka, is a modern, concrete-and-glass building packed with the latest high-tech fly-rearing equipment. Its insides bristle in shades of stainless steel and plastic. It was designed to produce up to 500 million sterile flies a week. So far, it has been lumbering along at a pace of 40 million a week.

The problems at the facility are legion. The heating system can’t keep the building hot enough. The humidity is not quite correct. The plant has become infested with another type of fly that eats the Medflies’ food.

There are dozens of variables in the touchy rearing process that might be off and no one is certain which are to blame. Is it the diet? Is it the humidity? Maybe it’s the way the trays of larvae are stacked, which could hamper air circulation?

“Right now, it’s not the best, but it’s the best we can do,” said Glenn L. Hinsdale, facility director.

The problems in many ways are inherent to starting a large facility such as Waimanalo. “It’s still an art,” said Roy Cunningham, a U.S. Department of Agriculture entomologist and the chairman of the state’s Medfly Science Advisory Panel. “They’re trying to make it a science, and they still have a long way to go.”

Even Tanaka has experienced problems with his far simpler operation. He once received a bad shipment of wheat, used for fly food. The wheat was contaminated with a small amount of malathion--just enough to wipe out an entire batch of flies. In the current push to increase shipments to California, he’s had workers spill jugs of fly eggs and barrels of larvae.

Tanaka said the problems at his facilities and Waimanalo are to be expected and eventually will be ironed out.

Agricultural officials believe that when the Waimanalo plant reaches full potential, Southern California may never have to face the repeated aerial malathion assaults that have inflamed the region.

In the meantime, the political and economic stakes riding on the success of the sterile fly technique are high. The state has only two weapons--sterile flies and malathion--to fight the Medfly, a voracious pest that could do substantial damage if it reached California’s agricultural regions, producers of over half the nation’s fresh fruit and vegetables.

Voss said in an interview that repeated malathion spraying is becoming unacceptable because of the intense public opposition. Thus, sterile flies offer the only feasible long-term strategy.

“The whole desire of society is to have less amounts of pesticide used,” Voss said. “It’s very likely even one spray may become unacceptable. In the long term we have to move away from where we are.”

But he said no matter how well the state plans for the future, there are no guarantees when it comes to dealing with the unpredictable Medfly.

The Medfly stunned officials last winter when the infestation spread like wildfire throughout Los Angeles and Orange counties. And there is always the grim possibility that another infestation the size of the 1,300-square-mile Northern California outbreak of 1980-82 could hit again and throw their plans to the wind.

“I think we are far better prepared today,” Voss said in a recent interview. “But how prepared is prepared?”

CANDIDATES ON SPRAYING--Democratic gubernatorial hopefuls Dianne Feinstein and John Van de Kamp call for an end to spraying. A22

SUPERVISORS ON SPRAYING--A bitterly divided Board of Supervisors voted Tuesday to extend Orange County’s Medfly emergency. B1

MEDFLY SPARYING MAP: B2