State agricultural officials have devised a plan to rid Oahu of the pesky little fire ant. They unveiled the plan Friday. In a few weeks, Hilo's Hawaii Ant Lab will train state crews in the treatment of a 3-and-a-half acre area of Waimanalo, including a 2-and-a-half acre buffer zone. The treatment includes a combination of pesticide baits. It will be administered and repeated eight times over a 12-month period. Robert Curtiss, acting manager of the state Department of Agriculture Plant Pest Control Branch, says if the area is clear of the ants at the end of the 12 months, the treatment will end, and monitoring will continue for three years. A University of Hawaii study estimated that Oahu could face $170 million a year in losses if the pest is allowed to spread unimpeded.