FOREST GROVE, Ore. — 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.

Larva from the emerald ash borer burrows into the bark of ash trees, causing canopy dieback and, ultimately, tree death. Signs of infestation may include thinning and yellowing leaves; bark splitting; D-shaped holes in the tree bark; and basal shoots.

So far, emerald ash borer has only been found in several ash trees in Forest Grove, according to the Oregon Department of Agriculture.

To prevent the pest from reaching other parts of the state, ODA has implemented the quarantine restricting the movement of certain tree materials — including logs, green lumber, nursery stock, scion wood, bud wood, chips, mulch, stumps, roots, branches and firewood.

Materials exempted under the quarantine include seeds and leaves; processed lumber that is kiln-dried, free of bark and any underlying wood 1 inch below bark; and finished wood products without bark, such as furniture, baskets and baseball bats.

ODA has also set forth several treatments for potentially infected ash, olive and white fringe tree material. They are:

• Debark and remove at least 1 inch of underlying wood.

• Grind or chip to 1 inch or less.

• Heat wood to a minimum of 140 degrees for at least 60 minutes.

• Bury under at least 12 inches of topsoil.

• Incinerate wood materials.

• Secondary processing to produce wood byproducts, such as paper, fiber board or wood pellets.

The quarantine will remain in effect until May 16, 2023. ODA will evaluate future quarantine parameters as more data becomes available.