DES MOINES, Iowa (AP) – Officials have found emerald ash borders in Polk County, home of the state capitol in Des Moines. A news release from the Iowa Agriculture Department said Friday that the tree-killing pests were found in Urbandale and West Des Moines. The department says the confirmation brings to 22 the number of Iowa counties where the insects have been found.

The larva of an emerald ash borer cuts off an ash tree’s flow of nutrients when deposited below the bark. Once infected, trees typically die within five years. The insects are native to Asia and were first spotted in the U.S. in 2002, when they showed up in the Detroit area. They devastated ash trees in Michigan and have spread to at least 21 other states.