Despite the discovery of four Mediterranean fruit flies in the San Fernando Valley, Ventura County officials are not worried about a similar infestation.
Last week, when the discovery of two fertile, female flies signaled that hundreds more could exist, Gov. George Deukmejian declared a local emergency for Northridge, less than 10 miles from Ventura County. A 16-square-mile area was sprayed aerially with the pesticide malathion Monday night.
But Don Anderson, Ventura County's deputy commissioner of agriculture, doubts that the fruit-devouring pests will migrate into the county, where no Medfly has been found.
Anderson had no theory to explain why Ventura County has been spared.
"We've just been lucky," he said.
Dr. Isi Siddiqui, assistant director of the state Department of Food and Agriculture, suggested that the county may be free of them because it has no major airport.
Travelers often bring the pests into California with illegally imported fruit, Siddiqui said. This is not likely to happen in Ventura County, where airports accommodate only local flights.
To kill the flies, state officials first spray with malathion bait, then release thousands of sterile adult Medflies into the area. Bred in Hawaii and made impotent with radiation, the swarms of extra flies make it nearly impossible for a fertile Medfly to find a suitable mate.
Adult flies are harmless to crops, since the Medfly only attacks vegetation during its larval stage. In the past, only sterile Medflies have been found in Ventura County, Siddiqui said.