California Gov. Edmund G. (Jerry) Brown Jr., charging political "sabotage" by Washington, angrily agreed today to spray pesticides from the air over a heavily populated area of northern California to forestall a federal threat to quarantine all of the state's fruits and vegetables.

Denouncing the quarantine threat by Agriculture Secretary John R. Block, Brown said the state will begin aerial spraying Monday to prevent further infestation by the larvae of the Mediterranean fruit fly.

Brown had asked for more time to try a ground spraying and local quarantine program favored by area residents but considered inadequate by California growers, state legislators and federal officials, who feared spread of the Medfy into other agricultural areas.

Block, at a Washington news confrence, declined to be drawn into name-calling with the governor, but he held open the possibility that a quarantine still might be in oder despite the decision to move to aerial spraying. Further evaluation will be made this weekend, he said.

Citing fears that the Medfy might infest other important growing areas, Block siad he had "no alternative" but to order a statewide quarantine if California did not take "severe immediate action," including aerial spraying, by Monday.

The secretary and other top USDA officials insisted that the ground-spraying and tree-stripping approach ordered by Brown this week to combat the Medfly was inadequate for dealing with the threat to fruit and vegetables in California and other states.

The appearance of the tiny insect in the area north of San Jose has threatened $545 million in annual California food exports and caused concern among growers throughout the rest of the country. California produces about half of the nation's fresh fruit and vegetables.

The Medfly dispute also has trapped Brown, a former presidential candidate planning a U.S. Senate race next year, between angry growers and state legislators on one side and environmentalists and local residents on the other, who fear public health and property may be endangered by the aerial application of malathion.

"We are being forced into aerial spraying," Brown said. "The action of the Reagan administration in threatening a quarantine is sabotage." He said he tried but failed to talk to President Reagan this morning and was first told a quarantine would be ordered today. He protested that it would take time to "establish safety measures and properly inform the residents."

"They have rejected our program of ground spraying in favor of aerial spraying which threatens the well-being and personal security of 500,000 residents, including pregnant women, infants and children," Brown told a news conference at the Century Plaza Hotel. "We must draw the line against the further spread of deadly chemicals in our environment and in the food we eat."

Two congressmen from the area that will be sprayed, Democrats Norman Y. Mineta of San Jose and Don Edwards of Santa Clara, denounced the USDA quarantine threat as a result of "hysteria" in the agricultural community.

Mineta said Block "jumped the gun" and Edwards accused the Reagan administration of trading off public health concerns "in response to agriculture's biased convictions that only spraying will work."

Brown said he grudgingly agreed to aerial spraying because to statewide quarantine would not only have severely affected California's economy but would have required massive fumigation of any fruits and vegetables leaving the state.

"I am not prepared to expose thousands of workers to the peril of deadly fumigation poisons which would be let loose by the Reagan administration order," he said.

Dianne McKenna, mayor of Sunnyvale, where the first aerial spraying is expected to begin, viewed the controversy in a different perspective. She said "the governor showed courage in standing up to the agricultural community." She said she did not yet know what she was going to do to protect her children, pets and birds in an outside aviary from the spraying.

Patricia Susedo, a San Jose City Council member, said if the nightime spraying came to her area, which she thought was possible, she would close her doors and windows and wash down her car the next morning.

Medfies lay eggs inside fruits and vegetables. Their hatched larvae feed on oranges, avocadoes and dozens of other products until they are soft and unmarketable.The first flies were found a year ago in Alameda and Santa Clara counties, believed brought in from Hawaii.

A $22 million fruit-stripping and ground-spraying campaign, augmented by the release of sterile flies to disturb the life cycle, was thought to have solved the problem. But Medfly larvae, which resemble small maggots, were found late last month in Sunnyvale and Los Gatos, leaving agricultural officials to suspect some of the sterile flies shipped from Peru were actually fertile.

USDA officials in Washington said that the Medfly has been detected in fruit at 100 sites, although none is a commercial growing area, giving rise to a fear that the infestation has spread to points not yet identified.

Brown's order to employ aerial spraying, using malathion, a common insecticide, will cover a 97-square-mile area in parts of Santa Clara County, the core of infestation, and two neighboring counties. Similar aerial spraying was considered completely effective against fruit flies in the Miami area in the 1950s and 1960s and in Brownsville, Tex., in 1966.

Some residents of the area between Palo Alto and San Jose said they feared the chemical could cause birth defects or other diseases in humans, but government toxicologists say it is only harmful if used in quantities far greater than would be involved in the spraying.

The malathion, according to USDA, will be applied at a rate of 2.4 onces per acre, in combination with larger amounts of a protein-based syrup, whose odor attracts the flies. Once they inject or contact the malathion, an organic phosphate, they die within a day of respiratory failure.