KIMT-TV: The Iowa Department of Agriculture says the emerald ash borer has been detected in two more counties. That means the destructive insect that kills ash trees is now present in 41 Iowa counties. The latest finds were in Bellevue in Jackson County and Marquette in Clayton County. The ash borer has spread to 29 states since it first appeared in Michigan in 2002. It is commonly spread when firewood is transported from one location to another.