THIS WEEK'S aerial spraying of malathion in northern California to exterminate the Mediterranean fruit fly has prompted some concern locally about the fruits and vegetables sold in the Washington area. According to California state agriculture department spokesmen and experts here, there is no reason for Washington consumers to worry.

Spokesmen here from both Giant and Safeway said that they are not receiving any produce from the quarantined area. The affected California counties are residential and urban communities where many homeowners have fruit trees in their backyards. There are a few farms that supply the immediate area, but produce there is not generally grown for interstate commerce. Fruits and vegetables shipped to Washington come from large commercial farms in other countries.

The spraying is intended to prevent the medfly from spreading. The infestation is a danger to the fruits and vegetables themselves, and does not pose a health hazard to anyone who might take a bite from infested produce.

According to Harvey Ford, deputy administrator for the Animal and Plant Health Inspection Service (APHIS) in the USDA, the infestation occurs when the female adult Medfly deposits its eggs in the fruits or vegetable. The eggs hatch into larvae or maggots and remain inside the food, eating their way out. According to Ford, you may not be able to tell from the outside that a peach or orange is infested, but the fruit would be soft inside and eventually turn mushy. Although most people wouldn't knowingly eat an infested piece of fruit, Ford said, "If you eat it, it wouldn't hurt you."

Eventually larvae exit from the fruit or vegetable, drop to the ground and bury themselves there until they have grown into adult flies, thus starting the cycle again.

The problem comes, says Ford, when an infested fruit or vegetable is disposed of improperly, allowing the larvae to continue to grow and infest other plants.

Skip Shorb, president of Shorb & Sons, one of the Washington metropolitan area's home and garden distributors, said malathion "is one of the two most popular insecticides for home garden use." According to California state agriculture spokesman Pope, "farmers use malathion all the time in commercial farms."

The highest amount of malathion residue that the Environment Protection Agency allows on fruits and vegatables that are to be shipped is 8 parts per million. Furthermore, according to Herb Harrison, chief of the insecticide division of the EPA, malathion "hydrolyzes into the atomosphere very quickly." Marueen Hinkle, a policy analyst for the Audubon Society, formerly a pesticides expert for the Environmental Defense Fund, added that "there is a long period of time between spraying and eating." Still, she warned, "Tolerances are based on an assumption that people will wash the fruit."