Edna-Kay Jamati, a nurse with three children, began shutting the windows in her yellow three-story house as soon as she heard the helicopters.

"It was like waiting at wartime for the bombs to be dropped, like something I had no control over," she said. There were no explosions, just an invisible rain of pesticide droplets falling over this California suburb in a war against an insect.

The Jamati home at 2422 Waverly St. sits just inside the first zone for aerial spraying to kill a three-county infestation by the Mediterranean fruit fly. If the effort to eradicate the insect, begun last night in the 120-square mile spraying area, does not succeed, half the nation's fruits and vegetables could be banned from leaving this state.

Meanwhile, the Medfly continued to spread. Jerry Scribner, head of the state's Medfly Project, said new larvae were discovered in the city of Milpitas, just outside the northeast corner of the 117-square mile area already targeted for spraying.

He said the target area, in the Santa Clara Valley south of San Francisco, would be expanded to include Milpitas.

The threat of high prices in supermarkets throughout the country and the ruin of California's $14 billion agriculture industry has warred with fears of residents here that the pesticide malathion might do longterm damage to unborn children or human nervous system.

A last-ditch effort by local jurisdictions, including the city of Palo Alto, to persuade a court to delay the spraying failed yesterday. State officials were slow to begin the spraying, however. "We're behind the fly right now," said Hans Van Ness, a deputy director of the state food and agriculture department, at a briefing for reporters this morning in Los Gatos.

California Gov. Edmund G. Brown Fr., who ordered the spraying only after federal officials threatened an immediate statewide quarantine, spent the night at a two-bedroom home in Los Altos to express his solidarity with local residents who had wanted to delay the aerial spraying to see if ground spraying, tree stripping and a local quarantine could defeat the insect commonly called the Medfly.

Only one helicopter was available for the first night's spraying and it covered only a strip about four miles long and one-third mile wide before the pilot had to quit because of a faulty pump. Van Ness said at least two and probably more helicopters would be available for midnight to 6 a.m. spraying runs in the next few days and the entire 120-square-mile area would be covered once every seven to 10 days until it was clear all flies had been killed.

Only 89 people made use of Red Cross shelters set up at schools and park buildings in Milpitas, Santa Cruz and San Mateo last night. Mary McLellen, director of disaster services for the Red Cross Santa Clara Valley chapter, said no one used a fourth shelter set up in Fremont. But she added that more spraying-area resident may use the centers as the helicopters proceed south from Palo Alto to San Jose.

Scientists continue to argue over conflicting research data on whether exposure to malathion can cause birth defects or cancer. A Harvard Medical School researcher said he has proven that the pesticide, related to nerve gas, can create changes in brainwaves and cause irritability in humans.

On Waverly Street, some residents have draped their automobiles with plastic covers. A few tiny automobiles with plastic covers. A few tiny sticky droplets of the bait that carries the pesticide rested on the plastic. Neighbors said, however, they noticed no odor or anything else unusual from the spraying.