Medflies Prompt Spray Plan : Insecticide: Limited dose of malathion in Oceanside is answer to two of the destructive insects found there.

If the rain clears, agriculture officials will begin small-scale malathion spraying today in southwest Oceanside, following last month’s discovery there of two Mediterranean fruit flies.

Officials plan a three-pronged attack on the Medfly, considered one of the world’s most destructive insects, including setting two types of bug traps and spraying a 33-block area with a mist of insect bait and malathion, a common pesticide. The area contains about 500 residential lots.

Meanwhile, quarantine boundaries are being drawn to prevent the spread of the Medfly via infected plants and produce. The quarantine will probably be made up of the city of Oceanside and a portion of Carlsbad, and last until next August, officials from the state Department of Food and Agriculture said Monday.

The Medfly is a threat to agriculture because it lives by boring holes in ripening fruit and laying its eggs inside. The eggs hatch maggots, which eat the fruit until it rots and falls to the ground. Then the maggots enter the soil, turn into flies, emerge and begin the cycle again.

Medflies will attack more than 250 species of fruits, nuts and vegetables, but prefer peaches, pears, plums apricots and cherries.

San Diego County has a $1 billion agriculture industry that would be threatened by a Medfly infestation, county Agriculture Commissioner Kathleen Thuner said. However, the appearance of only two flies suggests that Oceanside’s infestation is “fairly limited,” another official said.

Although Medfly infestations have appeared throughout California, and in three counties that border San Diego County, the pests rarely have been spotted here, officials said, nor has malathion spraying ever been used to combat them here.

One fly was found in November, 1980, and another in August, 1986, but both times traps were used to eradicate any others, Thuner said.

But, when more than one fly appears, as is the case this time, officials resort to malathion spraying from the ground. Aerial spraying is used only for widespread infestations.

In southwest Oceanside, one Medfly was found in a trap in a routine check near Cleveland and Eucalyptus streets Nov. 16. A second fly appeared Nov. 27, less than half a mile away. Both were females, one mature and one immature.

Officials are planning to spray the Oceanside area three times at intervals of two weeks. The spray, applied by a machine that looks like a leaf blower, is a mixture of 20% malathion and 80% Medfly bait, a sticky corn protein. Each spraying should last about two days and cover threatened plants from 5 to 15 feet from the ground.

Trying to allay residents’ fears about the spraying, state entomologist Brian J. Taylor said only 1 to 2 gallons of the bait-poison mixture will cover the entire 33-block zone. That’s about one teaspoon of liquid per property, he said.

“It is really minuscule,” Taylor said. “All we’re doing is killing flies, and it doesn’t take much.”

“It’s a typical pesticide. It’s not a super-special concoction,” said Peter Kurtz, senior medical coordinator for the state agriculture department. “You can find it in any hardware store.”

Nevertheless, officials say they will advise residents to keep their windows shut and their pets reined in during the spraying, and to carefully wash their produce before eating it.

In 1989, malathion was sprayed over El Cajon to kill Mexflies. Agriculture officials say 4 million to 5 million pounds of malathion are used each year in mosquito abatement programs in California. They say many studies have shown that the pesticide does not cause nerve damage, birth defects or cancer.

Hundreds of traps are also being deployed in the area, including 750 “yellow sticky panel traps” that lure the bugs with a male pheromone. One in three yards will get a yellow sticky panel trap.

Another 109 McPhail traps, a glass device with a yeast lure inside, have been set.

On Monday, officials also appealed to residents not to transport untreated plants or fresh produce out of the infected zone. They said the Medflies probably entered the area in illegal shipments of fruit from Hawaii or were brought in accidentally from the Los Angeles area.