Wallaces Farmer

Emerald ash borer found in yet another county in Iowa

Tree-killing insect keeps spreading, has now been confirmed in one-third of Iowa's counties.

March 8, 2016

4 Min Read

The emerald ash borer (EAB), which has already been confirmed in nearly one-third of Iowa’s counties, has been discovered in Decorah in northeast Iowa. This destructive pest, native to Asia, feeds on and eventually kills an infested ash tree. The Iowa Department of Agriculture on March 4 announced this latest finding.


Winneshiek County has been added to the growing list of 31counties in Iowa that have confirmed EAB infestations. This marks the second county in Iowa where EAB has been found this year. Last month EAB was found on the University of Iowa campus. This exotic pest was first detected in Iowa back in 2010 in Allamakee County. EAB has spread to 25 states where it is responsible for decimating tens of millions of ash trees.

New infestation of EAB recently discovered in Decorah
A consulting arborist was drawn to the tree in Decorah after noticing evidence of EAB damage. Further investigation revealed distinctive S-shaped galleries and an EAB larva (immature beetle) underneath the bark of the infested tree. The collected larva was sent to the USDA Systematic Entomology Laboratory where it was confirmed positive for EAB.

“We are fortunate that others are aiding in the effort and alerting us of trees that are suspect for emerald ash borer, especially in areas not yet known to be infested,” says Mike Kintner, Iowa Department of Agriculture & Land Stewardship EAB and gypsy moth coordinator. “Like other states, we will continue to track this pest as it expands to new areas.”

Small metallic-green beetle, emerald ash borer kills ash trees
The adult emerald ash borer is an elusive metallic-green beetle measuring approximately ½ inch long, making it challenging to detect in the landscape. The adult females lay eggs in the bark crevices of ash trees where they hatch, boring into the inner bark. During this immature stage the progression of larvae feeding and development disrupts the trees’ ability to transport water and nutrients. EAB infested ash trees include thinning or dying branches in the upper canopy, evidence of woodpecker activity, S-shaped feeding galleries under dead or splitting bark, D-shaped exit holes and water sprouts (along the trunk and main branches). 

Federal quarantines are in place to restrict the movement of hardwood firewood, ash logs, wood chips and ash tree nursery stock out of Iowa into non-quarantined areas of other states. The Iowa EAB Team urges Iowans to use locally sourced firewood, burning it in the same county where it was purchased. Firewood is not only a means of transportation for EAB, but other tree-killing pests as well.

Time to treat with insecticide for EAB is early-April to mid-May
At this calendar date, the window for all preventive treatments remains closed. If a landowner is interested in protecting a valuable and healthy ash tree within 15 miles of a known infestation, he or she should have landscape and tree service companies bid on work, review the bids and treat beginning spring 2016 (early April to mid-May).


Please contact Iowa EAB Team members to have suspicious looking trees checked in counties not currently known to be infested. Team members include officials from Iowa Department of Agriculture & Land Stewardship, Iowa State University Extension, the Iowa Department of Natural Resources, USDA Animal Plant Health Inspection Service and the U.S. Forest Service.

The State of Iowa will continue to track the movement of EAB on a county-by-county basis. Before a county can be officially recognized as infested, proof of a reproducing population is needed and an EAB must be collected by a member of the Iowa EAB Team and verified by USDA entomologists.

Emerald ash borer is one of the most destructive tree pests
The emerald ash borer (Agrilus planipennis) is perhaps one of the most destructive tree pests we have seen in decades. Larvae of this insect feed under the bark of ash trees. They damage the ability of the tree to transport water and nutrients, and may kill the tree in as little as two to four years.

To learn more about EAB and other pests that are threatening Iowa’s tree population, please visit IowaTreePests.com. Please contact any of the following members of the Iowa EAB Team for further information:

•Mike Kintner, IDALS EAB coordinator, 515-745-2877, [email protected]
•Robin Pruisner, IDALS state entomologist, 515-725-1470, [email protected]
•Paul Tauke, DNR state forester, 515-725-8450, [email protected]
•Tivon Feeley, DNR forest health coordinator, 515-725-8453, [email protected]
•Emma Hanigan, DNR urban forestry coordinator, 515-725-8454, [email protected]
•Jesse Randall, ISU Extension and Outreach forester, 515-294-1168, [email protected]
•Mark Shour, ISU Extension and Outreach entomologist, 515-294-5963, [email protected]
•Laura Jesse, ISU Extension and Outreach entomologist, ISU Plant and Insect Diagnostic Clinic, 515-294-0581, [email protected]
•Donald Lewis, ISU Extension and Outreach entomologist, 515-294-1101, [email protected].
•Jeff Iles, ISU Extension and Outreach horticulturist, 515-294-3718, [email protected]

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