State Claims End Is Near in Medfly Battle : Eradication: Agriculture chief is confident the worst is over, but at least one scientist says it is too soon for such optimism.

On the eve of the most critical breeding period for the Mediterranean fruit fly, top agricultural officials declared Thursday that the worst of the yearlong infestation is over and complete victory may come by the end of next month.

“We’re closing in and wringing the last drops out of the sponge. If we don’t find any more flies, we’re out of this in September,” Henry J. Voss, director of the state Department of Food and Agriculture, said in a confident assessment of the eradication campaign.

Voss presented his rosy prediction of impending victory at the monthly meeting of the 15-member state Board of Food and Agriculture, an advisory body to the governor on agricultural issues.

He said the lack of recent fly finds, and the quickly shrinking size of the infestation, have prompted state officials to believe they have finally gained the upper hand over the pest, which poses a major threat to the state’s lucrative agriculture industry.

Voss’ chief commander in the eradication effort, Assistant Director Isi Siddiqui, added that, despite continuing criticism about the effectiveness of the state’s campaign of aerial malathion spraying and sterile fly releases, the relatively small number of Medfly finds in the last few weeks confirms that the strategy has been successful.

“The worst of the infestation is over,” Siddiqui said. “We are optimistic that this infestation is on the way out. . . . What we have proved is that what we are doing is working.”

The optimistic assessments of the Medfly war come just as the pest enters what has historically been its active breeding season.

James R. Carey, a UC Davis entomologist and a member of the state’s Medfly Science Advisory Panel, said that since the first Medfly was found in California in 1975, about two-thirds of the pests have been trapped in August, September and October.

“I think it’s way, way too early to be optimistic,” said Carey, who spoke before the board Thursday to propose putting the eradication campaign on a permanent basis. “There is a natural seasonality to the Medfly. I’m not optimistic.”

The state also has had a dubious track record in predicting the flow of battle against the Medfly.

In January, Voss issued a similar prediction of victory only to face a startling resurgence of the pest in March and April.

As recently as late June, when Southern California went for nearly two months without a single Medfly find, Siddiqui and other agricultural officials were expressing similar optimism. However, that confidence was jolted by the discovery of a handful of Medflies that required a new round of malathion spraying around Rosemead, downtown Los Angeles and Glassell Park.

But this time, Siddiqui said, there are persuasive arguments to suggest that the end is really near.

No Medflies have been found in the last three weeks and only five in the last five weeks, he said.

More important, he pointed out, no larvae, an immature form of the pest that lives in the ripe fruit, have been found since January. The lack of larval finds indicates that the Medfly may be close to disappearing from the region.

Siddiqui said the state is also now far better prepared to battle the Medfly than at almost any point during the infestation.

Since the beginning of the eradication campaign, there have been acute shortages of sterile Medflies, which have forced the state to embark on aerial spraying campaigns. But as the size of the infestation has begun shrinking, the supply of sterile flies will eventually be more than enough to combat new outbreaks without repeated malathion sprayings.

About 305 square miles are now being treated with sterile flies. By the end of the month, the sterile-treatment zone will shrink to just 45 square miles, officials said.

No areas are now being sprayed with malathion, a factor that Voss said also has helped to lift the tense, crisis atmosphere that has pervaded much of the eradication program.

Voss cautioned that he expects to find a few more flies in the coming months. But he said the latest trapping information seems to indicate that the days of big discoveries that sent the spray zone skyrocketing to 536 square miles this spring are history.