Sterile Medfly Program Has Bugs, Experts Say : Agriculture: Despite a study that revealed the wild insects usually don’t mate with infertile counterparts, federal and state officials insist their fly releases, combined with spraying, are a proven success.

At a peach tree on the Hawaiian island of Maui, a paint-spattered Mediterranean fruit fly buzzes up to a female fly. He flaps his wings madly. He dances. He spritzes his cologne. And like so many other Lotharios on the prowl, he gets turned down cold.

That fleck of orange paint on his belly marked him as a sterile male Medfly. And his rejection by a wild female Medfly was one of hundreds of similar put-downs recorded during an experiment at the University of Hawaii last summer on the mating habits of the Medfly.

In the study, less than 2% of the sterile male Medflies wound up mating with their fertile female counterparts. And just 35% of the sterile females had trysts with wild male Medflies.

The findings are bad news for federal and state officials, who are dumping more than 560 million sterile flies each week in Southern California, including 27 million in the Westminster area alone, to wipe out four separate Medfly infestations.

“There certainly are some problems with the sterile Medfly program,” said Ken Kaneshiro, a University of Hawaii researcher who discovered the reluctance of wild Medflies to mate with their sterile counterparts. “The whole idea is for sterile males to mate with wild females.”

But state and federal officials, battle-scarred from now nearly annual wars against the blue-eyed Ceratitis capitata , insist their combined method of pesticide spraying and sterile fly releases is a proven success.

“We do know that we have been successful” in eradicating wild flies, said Robert Dowell, chief state entomologist.

That claim, though, is disputed by a growing number of scientists who say that Kaneshiro’s study and even more recent genetic research on the Medflies’ origin helps build the case that despite a $170-million eradication effort throughout California, the pest never has been wiped out.

Instead, they say, the destructive pest has made a home of the Golden State, a contention hotly denied by state and federal officials who insist that each appearance of the pest is new, the result of infested fruit being shipped illegally into the country from areas such as Hawaii, where the pest is endemic.

“They are not resident,” said Roy Cunningham, laboratory director for the U.S. Department of Agriculture research service in Hawaii. “The same people or the same groups of people are smuggling the fruit in. That’s quite evident.”

The issue is far from academic. At stake is the state’s $17-billion annual agriculture industry and the estimated $875.3 million annually it would take to battle a continual infestation of the pest.

“You’ve got to recognize this as a long-term problem,” said James Carey, a UC Davis entomologist and member of the Medfly project’s scientific advisory panel who has long insisted on the flies’ establishment here. “You’ve got to come up with a broader-based program.”

The debate comes at a time when the battle against the Medfly is heating up again. Though infestations typically don’t show up until late summer or fall, three flies have been discovered so far this year, including one earlier this month in Westminster and another one Friday in Ontario. More than 650 square miles are under quarantine in Southern California, meaning fruit may not leave or enter the area.

More than $38 million has been spent to wipe out the pest since it first reappeared in San Jose last August. About $52 million was spent fighting the Medfly infestation of 1989-90.

“So far, we are not pleased,” said Robert Dowell, the state’s chief entomologist. “If we keep getting them, yeah, it’ll be a bad year.”

The primary tool to control the flies is the dumping by land and air of sterile Medflies. The idea is that the wild Medflies mate with their sterile brethren and the population will hit a biological dead end.

But Kaneshiro’s research shows that wild female Medflies are extremely picky and the lab-raised sterile Medflies just can’t cut it when faced with competition from the wild males.

“In a wild population, there are duds and studs,” explained Kaneshiro. The “studs” are the 30% of the males that do 50% of the matings. The “duds” are the 30% of the flies that go to their graves virgins.

“The lab-raised, sterile males resemble the duds of the wild population,” Kaneshiro said. One reason, he says, is that the sterile male Medflies can’t adequately perform the elaborate courtship rituals demanded by the wild females. They dance funny, smell funny and don’t flap their wings as powerfully as their wild male counterparts, according to Kaneshiro.

As a result, even when sterile males outnumber wild ones 60 to 1, about 12% of all matings take place between two wild, fertile flies, Kaneshiro says.

To wipe out the flies, he says, the release of the sterile flies must be done for about twice as long as it is now, about nine to 10 months. That way, the resistance of the picky females breaks down, and out of desperation, they begin to settle for the sterile males--the actualization of “the-last-man-on-earth” scenario.

State and federal officials, however, say their current release program is effective. “We release them for four generations. That should be sufficient,” Cunningham said.

But other research--some of it based on DNA fingerprinting techniques commonly used in legal cases--is giving further ammunition to those who question whether the flies have ever been successfully eradicated from the state.

Genetic analyses of Medflies captured during outbreaks across the state in 1989, 1991 and 1992 show the flies are related. They appear to be unrelated to Medflies from Hawaii, the usual origin of infestations.

Carey says this bolsters his contention that the flies are resident here, a claim based mostly on their reappearance year after year at the same locations.

But state and local officials, pointing to another genetic study that has so far failed to rule out Hawaii as the site of origin of the California Medflies, dismiss the technology as too new to be trusted: “The fingerprinting is in a real infancy,” Cunningham said.

And, they say, the repeated appearances can be explained by better trapping in those areas, as well as a cultural predilection of residents in the area to get shipments of fruit from infested areas.