Fruit Flies Gone for Now but May Be Back in Spring

Los Angeles County agricultural officials say efforts to halt an invasion of Oriental and Mediterranean fruit flies in the county appear to have been successful, with no new finds reported since November.

“I feel very confident that we caught it in time and have prevented any further spread,” Los Angeles County Agricultural Commissioner Paul Engler said of the infestation.

But Engler and other officials say the pests may just be hibernating during the cold weather. Traps and a quarantine will remain in place at least through spring before the flies are declared eradicated.

Both flies pose threats to California’s billion-dollar agricultural industry.

Nearly 10,000 traps are scattered around the county to catch the flies. Oriental male flies are lured to the traps by a chemical that emits the scent of a female fly. County officials refer to the traps as “the male annihilation treatment.”

Similar lures are used to trap the Mediterranean flies, but the program is not as successful because of the quality of bait available. An infestation of Mediterranean fruit flies, which threaten more kinds of fruits and vegetables than the Oriental flies, often requires chemical spraying or intensive dumping of sterile flies in an affected area, officials said.

Aerial spraying and quarantine were used to combat an infestation of the Mexican fruit fly in a 63-square-mile area of central and South-Central Los Angeles. That infestation was discovered in October, 1983, and declared eradicated last August.

Since June, 92 Oriental fruit flies have been found in Los Angeles County, resulting in prohibitions against movement of nearly 100 host fruits and vegetables out of infested areas.

In August, a quarantine zone was established in the South Bay, and it was eventually expanded to an area that stretches from Santa Monica south to Torrance and Gardena. The area includes several hundred thousand homes. There have been no sightings since Nov. 14.

Beverly Hills Fly

On Nov. 20, a Mediterranean fruit fly was found in Beverly Hills. None have been spotted since and no quarantine to prevent the spread of the pest is in effect.

But Engler said it is too soon to declare the threat removed.

“Cold weather keeps flies hibernating in the ground so we don’t trap them,” Engler said. “They emerge from the ground and take off when the weather warms up.”

He said he believes the Mediterranean fly that was trapped in a Beverly Hills grapefruit tree was “just a hitchhiker” that probably arrived with fruit brought by a traveler from Hawaii.

“The person who brings in the fruit doesn’t know it has maggots or eggs in it,” Engler said. “We’re under constant pressure because of the volume of travel and the commercial shipments that come into Los Angeles County.”