Helicopters sprayed a pesticide over a 16-square-mile suburban area early Tuesday following the discovery of a third female Mediterranean fruit fly.

Two helicopters carrying 1,100 gallons of the pesticide malathion, mixed with a corn-syrup bait, began spraying the San Fernando Valley area at about 10 p.m. Monday, said county agriculture official Bob Don-ley.Each helicopter was scheduled to make three passes over the spraying area in a five-hour period, he said. Residents were warned to keep pets inside and to cover automobiles and fish ponds to prevent damage from the malathion.