The invasive Emerald ash borer has been confirmed in four more Iowa counties as the beetle continues to spread across the state.The insect has been found in ash trees in Buchanan, Hamilton, Hardin and Pottawattamie counties, according to a Friday news release from the Iowa Department of Agriculture and Land Stewardship.Since 2010, there have been 59 counties with a confirmed Emerald ash borer presence.The beetle was first found in Cedar Rapids in 2015 and again last July.