Officials Wary as Spraying Ends : Malathion: Wednesday’s flight over Compton was last one scheduled for Los Angeles County. But experts say they can only hope the hiatus of new fly discoveries will continue.

Late Wednesday night, a squadron of helicopters lifted off from Long Beach and flew a one-hour sortie over the city of Compton, carrying a final dose of malathion to fight a flare-up of Mexican fruit flies.

The mission was something of a milestone in a long and frustrating aerial war that has been waged over Southern California. After 10 consecutive months of regular helicopter excursions--first against Medflies and more recently against the Mexfly--the raid Wednesday was the final scheduled malathion spraying for Los Angeles County.

But there was no celebration. State officials can only hope that their luck will hold and the hiatus of new fly discoveries will continue.

If more flies are found, more spraying will probably be ordered, and experts say it will not be until late July that they can claim with confidence that the infestations have been eradicated.

“I’m not going to call it a victory,” said Don Henry, chief deputy director of the eradication campaign. “We still have to get through the middle of July. Then you’ll see us a little less somber.”

At its height, the state’s spraying campaign covered 536 square miles and reached into parts of five counties in Southern California. The sound of helicopters, rattling windows and sending pets scurrying for cover, became commonplace for more than 4 million Southern Californians, some of whom angrily fired back at the state’s aerial assault with a flurry of noisy protests and lawsuits.

But in the last month, the war against the Mediterranean fruit fly and its kin, the Mexican fruit fly, has become quiet.

The last malathion spraying for the Medfly in Los Angeles and Orange counties was conducted May 30 and no Medflies have been found in six weeks--the longest stretch since the beginning of the infestation last July. No Mexican fruit flies have been found since May 8.

With the final spraying in Compton, only 64 square miles in San Bernardino County, El Cajon in San Diego County and the Woodcrest area in Riverside County have been left with the dubious honor of being the last in the spray zone.

Despite the noticeable deceleration of the unpopular spraying program, the political heat continues. The Los Angeles City Council has been considering barring the state from using any airport in the city to launch its squadron of malathion-bearing helicopters.

In addition, demonstrations and press conferences attacking the spraying campaign have persisted, although at nowhere near the frantic pace of spring when the spray zone was growing in leaps and bounds.

“I think people are relieved and tired. They’re taking a breather,” said Patty Prickett, coordinator of the community group Residents Against Spraying Pesticides. “But there’s no way we are going to give up until we know this won’t ever happen again.”

The spraying campaign over the last 10 months has been the largest mounted in Southern California, involving more than 480 workers and costing an estimated $36 million so far.

The statistics of the campaign have been mind-boggling, even for veterans of the fruit fly wars. About 47,000 gallons of malathion have been dropped on Southern California. Close to 4 billion sterile Medflies have been released to breed the pest out of existence.

The questions about the success of the eradication program have persisted through these quiet weeks, driven by two disturbing factors that have left even eradication program officials wary and uncertain--a shortage of sterile flies and the warm weather ahead.

The state’s Medfly eradication program has been plagued with a serious shortage of sterile flies, which are released by the millions to disrupt the breeding cycle of the wild Medflies.

Because of production problems at three sterile-fly breeding facilities in Hawaii, the program has been receiving about a third fewer flies than what scientists have recommended.

Richard Rice, one of the five entomologists serving on the state’s Medfly Science Advisory Panel, has said that the shortage could open a “window of opportunity” for the wild flies to breed.

Eradication project officials also have expressed concern about the shortage, but add that the lack of flies is an encouraging sign that no serious damage has been done.

With many warm months ahead, offering ideal conditions for both flies, there also is the possibility of new discoveries popping up any day.

James Carey, a UC Davis entomologist and another member of the Medfly Science Advisory Panel, said the historical pattern of a Medfly population surge in late summer almost guarantees that more flies will be found.

Carey said that during the last 15 years in Southern California, only 9% of Medflies have been trapped from January through July, while 69% have been found in August, September and October.

“Based on that pattern, I’m not optimistic,” Carey said. “This is the lull before the storm. The only time I will be optimistic is if we go through the summer and fall without a single fly. Then I’ll be a believer.”

TALLYING MEDFLY COSTS Cost of Medfly eradication program (to June 1): $36 million Amount of malathion sprayed (as of May 30): 47,000 gallons Number of sterile Medflies released (as of June 1): 3.6 billion Number of people involved in eradication program: 487 First Medfly find: July 20, 1989 First malathion spray: Aug. 10, 1989 Maximum spray zone: 536 sq. miles Medflies found: 270 Mexflies found (from September, 1989 to present): 11 SOURCE: Cooperative Medfly Project