The emerald ash borer (EAB), an invasive pest from Asia, has been discovered in Crawford, Delaware and Page counties.
EAB has now been detected in 64 Iowa counties where it bores into ash trees and feeds on tissues beneath the bark, ultimately killing the tree.
Insect samples were collected from Denison (Crawford County), Edgewood (Delaware County), and Clarinda (Page County). Officials with the Animal and Plant Health and Inspection Service (APHIS) of the US Department of Agriculture (USDA) confirmed these samples positive for EAB.
“Despite emerald ash borer being linked to nearly two-thirds of Iowa’s counties, people are encouraged to report suspected infested ash trees in counties where it has not yet been confirmed,” said Mike Kintner, Iowa Department of Agriculture and Land Stewardship EAB and gypsy moth coordinator. “Tracking the whereabouts of emerald ash borer across the state is a useful component of treatment recommendations.”
EAB-infested ash trees can include thinning and dying crowns, water sprouts along the trunk and main branches, increased woodpecker activity that causes the tree to look like it is losing patches of bark, S-shaped galleries on the inside of bark, vertical bark splits, and 1/8-inch D-shaped exit holes where adult beetles emerged from the trees.
The larval stage feeds beneath the bark and disrupts the movement of water and nutrient within the tree. Once infested, ash trees continue to decline and usually die within 2-4 years.  
At this calendar date, the treatment window for soil-applied preventive treatment measures (soil injection, soil drench, or granular application) and basal bark sprays has ended. Trunk injections can be done now through the end of August if a landowner is interested in protecting a valuable and healthy ash tree within 15 miles of a known infestation.
Good soil moisture is critical for the effectiveness of any systemic insecticide movement in a tree. Full details are available in Iowa State University Extension and Outreach publication PM2084: https://store.extension.iastate.edu/product/13114. To find a certified applicator in your area, download PM3074 and follow the steps: https://store.extension.iastate.edu/product/Finding-a-Certified-Pesticide-Applicator-for-Emerald-Ash-Borer-Treatment.
The adult beetle can fly only short distances, but people have largely contributed to the spread of this pest by moving infested material, particularly firewood. EAB larvae can unknowingly be transported beneath the bark of firewood. People are reminded to help protect areas free from EAB by only purchasing and burning locally sourced firewood.