Oriental Fruit Flies Discovered in Poway : Agriculture: Traps are set, pesticide is sprayed in hopes of eradicating destructive pest.

Three more Oriental fruit flies were found in San Diego County, officials announced Tuesday, bringing to seven the number of potentially destructive flies that have been discovered over the past two weeks.

Starting today, the 7-square-mile pesticide spraying area in Mira Mesa and Scripps Ranch, where the first pests were discovered, will be expanded by 9 square miles to include Poway, where the latest find was made.

State and county officials who are cooperating to eradicate the Oriental fruit flies said Tuesday that it is too early to tell whether a full-fledged, crop-threatening infestation is under way.

They are confident the peril can be controlled by carefully hand-spraying trees and utility poles with a pesticide-laden lure containing a sex aroma that attracts mature male Oriental fruit flies. No aerial pesticide spraying is taking place.

“The significance of this (latest) find is primarily that we have had to enlarge the treatment area,” said Martin Muschinske, an entomologist with the state Department of Food and Agriculture’s local office.

Last week, when the first three flies were found in Mira Mesa and Scripps Ranch--a fourth fly was located in Hillcrest--teams of state and county workers began squirting lure on about 4,200 trees and poles.

Workers also set hundreds of traps for the yellow-striped fly that attacks 236 kinds of fruits and vegetables, some of which are multimillion-dollar crops in San Diego County.

David Kellum, supervising entomologist for the county Department of Agriculture, Weights and Measures, said about 600 trees and poles will be sprayed for every square mile of the new target zone in Poway. Spraying will be done every 50 yards.

The latest Oriental fruit fly discovery “indicates there is something happening here,” Kellum said. He cautioned the danger probably isn’t great unless larvae are found, meaning the fly is reproducing.

“When we start finding larval stages in fruit, we know the fruit fly has successfully survived and is laying eggs,” Kellum said.

Officials hope to quickly quash the fast-multiplying menace before its numbers increase. Normally, three or four Oriental fruit flies are trapped each year in San Diego County, so officials are concerned, though not yet alarmed, that the number has reached seven.

Muschinske said, “there’s no way of speculating whether there’s been any propagation” of fruit flies. He said the Oriental variety is especially vulnerable to the deadly sex-scented lure.

The latest flies were trapped in a fig tree in the yard of a single-family home, officials said. The approximate center of the new pesticide treatment area is Stowe Drive and Pomerado Road, about 2 1/2 miles from the spot where the first fruit flies were discovered.