Following the discovery of a third female Mediterranean fruit fly, agricultural officials on Monday sent ground crews to spray malathion pesticide on fruit trees in Maywood and Bell and declared a quarantine on produce grown and sold in a 76-square-mile area southeast of downtown Los Angeles.
The steps were taken to halt what one state official called the first Medfly infestation in California since the statewide plague of 1980-81, which caused an estimated $73 million in crop damage and cost more than $100 million to eradicate.
More Flies Expected
The trapping of five more suspected Medflies on Monday fueled official concern, although the insects have not yet been positively identified. The flies were found in monitoring traps within three miles of a peach tree on Palm Avenue in Maywood where the third confirmed Medfly was discovered Sunday, said Los Angeles County Agricultural Commissioner Paul B. Engler.
"Candidly, we expect to find more (Mediterranean fruit) flies in that area," Engler said at a news conference in his El Monte office, "so there might be an expansion of the quarantine and there might be an expansion of the ground treatment area."
In addition, officials are preparing to release millions of sterile male Medflies in about 30 days in what amounts to a massive birth-control program, Engler said. By mating with the sterile males, female Medflies will, in effect, breed themselves out of existence.
"We're talking the biggest threat to California agriculture that I can imagine," Engler said, "because right here in Los Angeles County we have a springboard for a spread to the entire Southern California (region)," including the fruit-producing areas of Orange and Ventura counties.
The Medfly is at "the top of the list" of crop-damaging pests, Engler said, because they prey on more than 200 varieties of produce, reproduce rapidly and survive in a range of climates.
The current infestation probably began with flies that arrived on fruit shipped into California illegally through the mails or carried in by returning tourists.
"I can assure you, the (Med)fly didn't fly in. It's being carried in by people," Engler said.
The quarantine declared by the state and federal Agriculture departments bans the transportation of produce outside a restricted area bounded on the north by the Santa Monica and Pomona freeways, the west by Central Avenue, the south by Imperial Highway and the east by Lakewood and Montebello boulevards.
Under the quarantine, the sale of produce by street vendors is banned and nurseries must comply with regulations that may require them to strip fruit and treat some potted plants or trees, said Michael Myers Jr. of the U.S. Department of Food and Agriculture.
In addition, Myers said, "we will be asking individual homeowners not to move backyard fruit or vegetables" outside the area. The quarantine will be enforced by federal agriculture workers, Myers said.
State agriculture teams on Monday were to begin spraying a combination of malathion and a yeast that acts as Medfly bait on fruit trees in a square-mile area in Maywood and Bell that is bounded by Atlantic Boulevard, Pine Avenue, Beck Avenue and the Long Beach Freeway, said Dorthea Zadig of the state Department of Food and Agriculture.
The crews will not spray entire fruit trees, Zadig said. Instead, they will spritz the pesticide and bait on small sections of the tree. Homeowners will be notified before their trees are sprayed, she said.
About a month after the last live Medfly is discovered, workers will begin releasing the sterile males, which are bred in a laboratory in Hawaii. The exact number will depend on how large the infestation becomes.
Single Medflies have been found in Los Angeles, Santa Barbara and San Diego counties in recent years, Zadig said, but the discovery of the three female Medflies in the Maywood area amounts to the first infestation in the state since 1981, she said. At the moment, the problem is minor, Zadig said. However, she added, "we could find more (Medflies) and it could change every day."
The five suspect flies found Monday probably are Medflies, Zadig said.
"A fresh Medfly is so colorful," she said. "The eyes are bright blue; the body is very brightly colored. It's very hard to mistake it for something else."
The five flies are being flown to Sacramento where they will be dissected and analyzed to determine if they are male or female and whether they have mated.