Teams from the state Department of Food and Agriculture sprayed pesticide in the backyards of 144 homes in a program to eradicate the pest, an aphidlike bug that can carry a bacterial disease fatal to citrus trees.

In South Bay Terraces, a neighborhood just north of Bonita, almost 500 sites are being treated with pesticide. It’s the first area in San Diego County to get the extensive treatment since the citrus psyllids were discovered in the county in late August.

Similar treatments are planned for El Cajon, Jamul, Dulzura, Tecate and locations in Imperial County, department spokesman Steve Lyle said. The work is expected to be completed by late November.

The department is also carrying on a separate battle against the Mediterranean fruit fly, which can attack more than 250 types of fruits and vegetables. Three Medflies were found in traps in El Cajon on the southeast side of Interstate 8.

Millions of sterile male Mediterranean fruit flies were dropped by air over an 11-square-mile area of El Cajon. Blanketing an area with sterile male flies gradually wipes out the population because the female flies can’t reproduce and die soon after mating.

More than 1,200 traps were placed on citrus trees in South Bay Terraces, and the citrus psyllid showed up at 22 sites. All citrus trees within about a quarter-mile of the discoveries were treated with two pesticides.