Medfly Caught in Los Alamitos Back-Yard Tree : Pest: The adult male fly is the first found in Orange County since August, 1990, triggering an intensive trapping effort.

A Mediterranean fruit fly was found in a back-yard orange tree here, triggering an intensive trapping effort but no immediate need for a quarantine or pesticide spraying, state officials said Monday.

The male adult fly was found Friday in a trap set in the 4600 block of Green Avenue. It is the first Medfly to be found in Orange County since August, 1990, when a female was trapped in a Brea peach tree.

State agricultural officials said Monday that they have added 100 traps to the mile-square area around the find. Aerial or ground spraying of pesticide will only occur if more flies are trapped over a much wider area, they said.

“We hope it’s an isolated fly find that will not require any major effort to eradicate,” said Carl DeWing, spokesman for the state Department of Food and Agriculture. “If in fact we discover a major infestation in which there are flies over a wide area, that might trigger a different response. But as of now, we don’t see that.”

The voracious Medfly is dreaded by farmers and agriculture officials because it can destroy more than 200 California crops. A widespread infestation in 1989 and 1990 led to extensive aerial spraying of malathion, which provoked vehement protests in Orange and Los Angeles counties.

Because of a new, more effective trapping technique, state agricultural officials said they are able to better measure the presence of Medflies and avoid aerial spraying. Spraying from helicopters would occur only if a very large area is infested, DeWing said.

Fruit and vegetables in Los Alamitos are not quarantined, but state officials are asking people to keep home-grown produce at home.

“Although a single male Medfly does not require an agricultural quarantine, we’re strongly urging residents in the Los Alamitos area to keep back-yard fruit on their own premises,” DeWing said. “We don’t want to spread this, if in fact, it is an infestation.”

Medflies were declared eradicated by the aerial attack in 1990, but they started to invade Los Angeles again in October. The last Medfly found in Southern California was on Dec. 6, in Los Angeles, where three males were trapped. No aerial spraying has occurred there either, although more than 20 flies have been found in the 6-square-mile area around Country Club Park and Koreatown in Los Angeles since October.

A single fly was also found in San Gabriel, but it is considered an isolated incident.

State officials believe that Medflies are arriving in Southern California through illegally mailed shipments of fruit from Hawaii or Asian countries.

“A lot of people do this out of ignorance,” DeWing said.