BAY AREA
Sterile male medflies loosed in breeding war
Tactic is to entice females to mate with impotent bugs

State agricultural officials released 2.5 million sterile Mediterranean fruit flies in San Jose on Thursday, hoping the insects will have sex with wild females and debug a potentially serious problem.

Officials declared a medfly infestation in the city for the first time since 1992 after two of the insects were found in recent days in the Santa Teresa neighborhood in south San Jose, near Snell Avenue and Highway 85. The flies are not dangerous to people, but their larvae can destroy fruits and vegetables.

The 2.5 million sterile flies were released Thursday morning in a 10-square-mile area surrounding the neighborhood, said Greg Van Wassenhove, Santa Clara County's agricultural commissioner. He said the process would be repeated weekly for about nine months, and officials will monitor hundreds of traps in a wider area to see if other medflies show up -- particularly in the spring, when a new generation might appear if the preventive steps don't work.

Van Wassenhove said typical medflies live only about a month, and that as long as the county is able to stop them from reproducing, they should go away. By releasing so many sterile males, agricultural officials hope to dramatically reduce the chances of a female reproducing.

The state Department of Food and Agriculture is also using a bacteria extract called Naturalyte in a 220-yard radius around the two spots where the medflies were found. It acts as a bait and kills the bugs but won't harm people, Van Wassenhove said.

More medfly traps have been set in an 81-square-mile area around the Santa Teresa neighborhood, and Van Wassenhove expects a quarantine will be imposed within a week to stop people from taking home-grown produce out of that area. Those who do so could be fined. Commercial growers would have to get the county to certify their produce was medfly-free before they could sell it.

Van Wassenhove said a few more flies might show up in traps in the coming days and weeks, but he doubted that any other steps would be necessary unless larvae appear in the spring.

Swarming an area with the sterile males has been an effective tactic against medflies since it was first tried in Southern California in 1996, said Steve Lyle, a spokesman for the Department of Food and Agriculture. When the Bay Area had more serious infestations in 1981 and 1989, the pesticide malathion was sprayed to control the bugs, but Lyle said the more natural method had worked better.

"We release hundreds of millions of sterile medflies in the L.A. Basin a week," Lyle said. "It's evolved past what people remember in some cases -- helicopters spraying pesticides."

During the infestation in 1981, people were so concerned about the dangers of pesticides that California Conservation Corps Director B.T. Collins drank a glass of diluted malathion to prove it wouldn't hurt people.

But malathion is now a distant memory. Lyle's department said the preventive program had drastically reduced medfly infestations.

From 1987 through 1994, the state averaged 7.5 medfly infestations a year. Since the program began in 1996, there have been only four infestations statewide, the department said.