EL CAJON - Authorities keep finding Mediterranean fruit flies around eastern San Diego County, but believe a daily air drop release of sterile male flies, ground treatments and a quarantine will defeat the pest menacing a local industry.
The third discovery of an invasive pest in San Diego County within the last year has proven unsettling and a bit of a mystery. Treatments and quarantines are in effect for Asian citrus psyllid and Diaprepes root weevils in the county that has a $1.5 billion agricultural economy set amidst the nation's sixth-largest city.
"Finding out who brought in the Medflies is tough," said Bob Atkins, San Diego County agricultural commissioner. "They are not likely from Mexico. We have people going door-to-door (in the) area trying to pinpoint this. Hopefully, we'll find something, but we don't have the smoking gun."
Eric Larson, executive director of the San Diego Farm Bureau, said the pests didn't get in on their own.
"They came from people smuggling fruit or produce," Larson said. "We're finding them in the urban areas, not on the farms. This will continue to be a problem."
Medflies can infest 260 types of fruit and vegetables, threatening the local agricultural economy and up to $1.5 billion in statewide production should it spread, according to agricultural officials.
Quarter-inch long, black-and-white Medflies were discovered and treated this year in Santa Clara, Los Angeles and Solano counties, Atkins said. Locally, a 2002 infestation at Valley Center, about 30 miles north of El Cajon, was treated successfully after much alarm.
The first state Medflies were spotted at Culver City in 1975 with 30 reported sightings and seven infestations - defined as two or more Medflies in a defined area - statewide since 1996.
"We've eradicated every Medfly infestation in California since we started," said Larry Hawkins, a U.S. Department of Agriculture spokesman.
A joint state-federal $17-million-a-year preventive treatment program using sterile fly drops and other measures, centered in the Los Angeles Basin, has been successful in preventing more serious outbreaks, Hawkins said.
Ground treatments using Naturalyte - a bait mixed with spinosad, a naturally occurring extract from bacteria - also were taking place this week primarily at a 500-acre avocado orchard and other sites. The treatments are being use in a one-eighth-mile radius from the initial fly detections, according to Steve Lyle, a spokesman for California Department of Food and Agriculture.
"We're going to treat two generations and monitor for a third," Atkins said. "We'll have a quarantine in effect asking that home-grown fruit stay at home."
Should no more flies be found, the airdrops and quarantine would end in late February or March. However, the stop clock will be reset any time a new fly is found, so the pest event may last longer, officials said.
The joint CDFA/USDA Medfly Preventive Release Program now breeds enough sterile fruit flies to release year-round, providing a constant swarm to the San Diego County Medfly fight. Overwhelming any egg-laying females with sheer numbers of impotent suitors ends the infestation when the females die after about three months of laying sterile eggs.
While successful to date, the program also has come under some scrutiny. Critics say Medflies are indigenous to the state and can never be wiped out from the air. They call for a long-term research program to identify other options to treat infestations.
The El Cajon quarantine area has yet to be fully defined, but the main areas of fruit fly discovery were near John F. Kennedy Park and Granite Hills Drive in El Cajon, primarily urban areas around Interstate 8, about 20 miles east of downtown San Diego.
Officials said state workers would inform those in the quarantine area of the fruit movement restrictions supplemented through appeals through the media to the general population.
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