UNIONVILLE, Mo. -- Missouri's northern borders continue to be on the front lines of stopping the spread of invasive tree pests. In early June, the emerald ash borer (EAB) was found in Davis County, Iowa, near the town of Bloomfield, which is less than 20 miles from the Missouri border. EAB, which kills ash trees with its tunneling under bark, has been found in 24 counties in Iowa and 11 counties, plus the City of St. Louis, in Missouri. Many invasive forest pests threaten to enter Missouri and cause serious damage to our forests and ornamental trees.