FOREST GROVE, Oregon — Oregon agriculture officials have adopted a temporary quarantine to slow the spread of emerald ash borer, a highly destructive forest pest that has killed hundreds of millions of native ash trees in North America. The quarantine limits the movement of ash, olive and white fringe tree material from Washington County, where the insect was found in late June in several ash trees at a middle school parking lot in Forest Grove, about 25 miles west of Portland. Native to Asia, the emerald ash borer first arrived in the U.S. in 2002, near Detroit, Mich. Since then, it has spread across 30 states and Canada. The discovery earlier this year in Oregon marked the first sighting on the West Coast. …So far, emerald ash borer has only been found in several ash trees in Forest Grove, according to the Oregon Department of Agriculture.