HARRISBURG, Pa.—The state Department of Agriculture says the emerald ash borer has been found in Mercer County.

The invasive beetle was discovered in Butler and Allegheny counties last summer. Officials are surveying this year to gauge whether the insect has spread.

Mercer joins Allegheny, Beaver, Butler and Lawrence counties in a quarantine prohibiting the movement of ash nursery stocks, green lumber and firewood.

The emerald ash borer is a wood-boring beetle native to China and eastern Asia. It has killed more than 30 million ash trees in Michigan since 2002 and millions more in Ohio, Indiana, Maryland, Virginia and Illinois.