State Escalates Medfly Battle : Agriculture: Discovery of mated female in Westminster prompts officials to release millions of sterile flies.

State workers dumped nearly 21 million sterile Mediterranean fruit flies by truck and by plane into dozens of residential neighborhoods Friday after the discovery of a mated female added urgency to the campaign to quash the pest.

The massive release is aimed at getting the sterile flies to mate with their fertile brethren, short-circuiting the reproductive cycle of the pest and bringing about its eradication.

A mated female was identified late Thursday among the 23 Medflies and six larvae that state workers have found in the neighborhood around Newland Street and McFadden Avenue since last week.

The discovery turned up the heat on the workers, who had sprayed the pesticide malathion in the area that day and planned on releasing the sterile flies next week.

“It is always distressing to find a mated fly,” said Robert Dowell, the primary entomologist for the state Department of Food and Agriculture. “This guarantees that flies now are mating and this is really the time to put those steriles out.”

The majority of the 21 million flies planned for release were dumped yesterday, with 1 million distributed in a square-mile area centered on Newland Street and McFadden Avenue and another 18 million scattered by planes that flew in a nine-square-mile area around the intersection.

Nor will the effort stop there. State workers will release 26 million sterile flies per week for the next nine to 10 months in a 25-square-mile area around the intersection near where three flies were found in a back-yard peach tree last Friday.

State officials said most residents will not notice the bugs, which flock to fruit and vegetable crops and are not dangerous to humans or animals.

Neighbors in the area gawked as the slow-moving truck went by Friday, a worker in the back shaking white-paper buckets in an effort to dislodge the pink, irradiated flies.

“Hey, do those things attack avocados?” yelled Mickey Nelson as he looked up from working on his motorcycle in his garage. When a worker told him the bugs were sterile, he seemed relieved.

“I haven’t had any problems so far,” he said of his four avocado trees. “It looks like they’re taking care of it.”

But scientists who study the creature questioned the effectiveness of the strategy.

“There certainly are some problems with the sterile Medfly program,” said Ken Kaneshiro, director of the Center for Conservation Research and Training at the University of Hawaii.

In tests carried out at the university, Kaneshiro found that only 2% of sterile male Medflies wind up mating with fertile female Medflies and that 35% of sterile female Medflies mate with fertile male flies.

In other words, Kaneshiro’s research shows that the wild flies don’t exactly jump at the chance to mate with sterile partners.

Fly Wars Sterile Mediterranean fruit flies were released by truck and airplane over a nine-square-mile area in an attempt to eradicate the latest infestation of the destructive pest.