Invasive, ash-tree-killing insect now present in all Iowa counties

By Cami Koons

The emerald ash borer, a non-native, wood-boring insect that affects ash trees, has been detected in all Iowa counties, the Iowa Department of Agriculture and Land Stewardship announced Thursday. 

The metallic-looking green beetle was first discovered in Iowa in 2010 and has made its way westward throughout the state through the inadvertent movement of infected firewood and other ash products. 

Emmet County, on the northern border of the state, was the final holdout. 

IDALS collected samples of a declining ash tree in Armstrong in early October and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service confirmed the sample. 

With the species present in all Iowa counties, landowners are advised to keep an eye on their ash trees and consider preventative insecticide treatments or removing declining ash trees. 

IDALS, Iowa State University Extension and Outreach, and Iowa Department of Natural Resources have guides and free resources for landowners. 

How to identify an ash?

The emerald ash borer lays its eggs in the cracks of ash bark and larvae will then bore into the tree, feed on the inner bark and disrupt the transport of water and nutrients through the tree. Once infested, an ash tree will usually die within two to four years. 

Infected ash trees will have thinning canopy, shoots along the trunk, serpentine feeding tracks from the larvae, and D-shaped exit holes. ISU Extension has resources on finding the right pesticide treatment for an infected tree and fact sheets on considering the value of an ash tree, which DNR estimates make up between 17% and 50% of street tree canopy in an average Iowa community. 

The department urged Iowans to burn firewood in the same community where it was collected to minimize the further spread of the ash borers. 

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