The emerald ash borer (EAB) is a destructive wood-boring beetle that attacks and kills ash trees (Fraxinus spp.). Adult EAB lay eggs on the bark of ash trees, and the larvae burrow into the bark. The larvae tunnel below the inner layer of bark, disrupting the flow of water and nutrients within the tree. The cumulative damage typically kills the tree within two to four years. Native to Asia, EAB was first discovered in the U.S. near Detroit, Michigan in 2002 and has since spread to over 35 states. This tiny insect is responsible for widespread ash tree mortality in Iowa and many other states.

Since October 2024, EAB has been confirmed in all of Iowa's 99 counties. Damage to ash trees in ongoing. The Iowa Department of Agriculture and Land Stewardship (IDALS) has been recording the spread of EAB since its initial finding in Iowa in 2010. See EAB county detection map. News releases have been issued for all first county detections. The most recent include the following:

Early symptoms in EAB infested trees are present in the upper third canopy of the tree. A common observed indicator is canopy thinning and dieback. These symptoms will gradually progress downward over time. Other indicators include 1/8 inch "D"-shaped exit holes, vertical splits in the bark, "S"-shaped feeding galleries in the vascular tissue beneath the bark, and woodpecker damage to the bark. As the tree declines, leafy sprouts often shoot from main branches and the trunk. When symptoms are present on lower branches and the trunk the tree is in steep decline. It may take anywhere between 2 to 4 years for a tree to die from an EAB infestation.

Ash trees are a commonly planted landscape tree in Iowa. Preventative treatment can be used to protect healthly and valuable ash trees. Treatment may also provide protection on lightly infested trees, provided the damage is minimal. Without ongoing treatment, any infested trees will die. Further details on emerald ash borer management options are available in this publication from Iowa State University Extension & Outreach.

USDA-APHIS ended the EAB federal domestic quarantine in 2021. However, each state has its own laws, and it is important for individuals and businesses to determine if regulations exist prior to the transportation of any EAB regulated articles outside of Iowa. Regulated articles may include firewood of any hardwood species, ash logs, ash chips/mulch, ash trees, green ash lumber and tree debris of ash. Contact IDALS for assistance with regulation status in other states.

While the restrictions on moving firewood within Iowa have been lifted, people are strongly encouraged to use firewood from local sources and 'Buy it Where You Burn it'. The use of locally sourced firewood can help prevent the inadvertent spread of damaging tree insects and diseases which can hitchhike in firewood.

Within its native range in Asia, several species of non-stinging wasps, or parasitoids, act as predators to help reduce EAB numbers. Scientists traveled to Asia to identify natural enemies of EAB. Once discovered, these insects were tested to determine that they would not negatively impact native species in the U.S. before being released.

The USDA-APHIS rearing facility in Brighton, Michigan produces and provides the parasitoids at no cost to cooperators for approved sites. Biological control for EAB has been implemented in over 30 states. In Iowa, IDALS serves as a USDA-APHIS cooperator with the biological control program using three species of parasitoids (Oobius agrili, Tetrastichus planipennisi, and Spathius galinae). Currently, biological control efforts have confirmed recovered parasitoids in seven Iowa counties since releases began in 2016.