Emerald Ash Borer Now Confirmed in all 99 Counties

First case of ash tree-killing insect confirmed in Emmet County 

DES MOINES, Iowa (Oct. 17, 2024) – Emerald ash borer (EAB), an ash tree-killing insect, has now been confirmed in all of Iowa’s 99 counties. Insect samples were collected from a declining ash tree in Armstrong earlier this month by staff from the Iowa Department of Agriculture and Land Stewardship. The sample was then sent to the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) for confirmation. With positive confirmation now in Emmet County, there are no remaining counties in Iowa without a detection.

EAB is a non-native, wood-boring insect threatening all species of ash trees. The adult EAB beetle is approximately one-half inch long and metallic green. The larval stage of this insect tunnels through the wood just beneath the bark of ash trees, cutting off the tree’s ability to transport water and nutrients. The cumulative damage typically kills a tree within two to four years after becoming infested. Indicators of an infestation may include canopy thinning, leafy sprouts shooting from the trunk or main branches, serpentine (“S”-shaped) galleries under the bark, bark splitting, woodpecker damage and 1/8-inch D-shaped exit holes.

EAB was unknown to North America until its discovery in southeast Michigan in 2002. The invasive, ash tree-killing insect from Asia has now been found in 37 states. In 2010, EAB was first discovered in Iowa in Allamakee County.

Landowners with ash trees on their property should begin to consider a course of action for at-risk trees, which are generally those within a 15-mile radius of a known infestation. Landowners and managers can wait and see what happens, remove declining ash trees and replace them with other species, or use preventive insecticide treatments to preserve and protect valuable and healthy ash trees. The best time to treat for EAB is in the spring from mid-April to mid-May. Insecticides are most effective when the ash tree is actively growing, and uptake is at its peak. Tree service companies can apply insecticide trunk injections through the summer if soil moisture is available.

Iowa State University Extension and Outreach has produced a publication about EAB treatments. For more information, download Emerald Ash Borer Management Options.

Since EAB as well as other invasive pests can unknowingly hitchhike in firewood, people are still reminded to use firewood locally sourced from the area where it will be burned to keep EAB and other tree-killing pests from being transported to new areas.
More information about EAB can be found at iowatreepests.com.