Federal officials last night were considering placing a quarantine on the shipment of fruit and vegetables from California's multibillion-dollar farm belt as a result of infestation by the hungry Mediterranean fruit fly.

As Department of Agriculture officials pondered options, denying reports that they had decided on a shipping ban, a full-scale shouting war was developing over California Gov. Edmund G. (Jerry) Brown Jr.'s refusal to order aerial spraying of the infested area near San Jose.

A spokesman for Agriculture Secretary John R. Block said last night that no decision had been reached, that meetings were continuing and that no announcement could be expected until today at the earliest.

But agriculture leaders in Florida and Texas, major competitors with California, were pressuring Washington for a nationwide quarantine on unfumigated produce for fear that any of it shipped into their states might spread the infestation.

And California politicians, here and in Sacramento, were angrily denouncing Brown's decision to attack the Medfly on the ground only. The state Senate voted 28 to 0 to go ahead with aerial spraying and the general assembly will continue discussions today.

Sen. S.I. Hayakawa (R-Calif.) decried Brown's move as "unwise." Rep. William Thomas (R-Calif.) was preparing legislation authorizing Block to take whatever steps he deems necessary -- including aerial spraying -- to control the spread of the Medfly.

Brown conceded, however, that the pest's presence in California's Fruit Bowl is a problem "that can devastate the agriculture of this nation. . . . This is a national problem and I do not believe many of the people understand how serious this problem is."

Unconfirmed reports here were that a USDA quarantine would cover the shipment of "host" crops infested by the flies, but marketing experts were uncertain what such a quarantine might entail.

Host crops include such staples as peaches, oranges, plums, tomatoes, nectarines, apples, avocados, bell peppers, bay laurel, and walnuts. Any interruption in shipments would have a quick effect on supermarket supplies and prices.

Brown, meanwhile, called out the National Guard to help combat the pest in a 60-square-area centered in Santa Clara County, and he invoked a plan to ground-spray thousands of acres where the larvae are found with poisonous malathion.

The governor's eradication effort was announced Wednesday for a 630-square-mile zone south and east of San Francisco after he rejected calls for aerial spraying over populated areas to control the Medfly and protect the state's rich agricultural industry.

The fly destroys many kinds of fruits and vegetables by laying eggs under the skin of its hosts. When the eggs hatch, the larvae feed on the fruit or vegetable, ruining it for commercial use. The fruit or vegetable remains edible although mushy. The Medfly spreads when infested fruit or vegetables fall to the ground and the larvae burrow into the earth and restart the cycle.

Only 100 fly larvae have been found this year, but agriculture officials says the flies can multiply rapidly unless attacked. To date, the flies have been found only in backyards; none has been found in the state's commercial orchards.

Brown ordered 1,000 National Guardsmen to duty to help homeowners in stripping fruit trees in a broad area around San Jose. Severl hundred workers were called in to spray malathion from the ground and the California Highway Patrol was ordered to search for fruit in cars leaving the huge quarantine zone that Brown has invoked in the state.

The governor refused to order chemical spraying from the air because, as he said, it would jeopardize "the sense of well-being and the security of 500,000 residents of Santa Clara County."

The Medfly returned this year after a similar effort of tree-stripping, ground spraying and releases of sterile flies in the fall and winter had been carried out at a cost of $22 million. State experts had predicted success of that effort as recently as last month, just before the 100 larvae were found.