A destructive pest of ash trees has now been confirmed in Buchanan, Hamilton, Hardin and Pottawattamie counties. The emerald ash borer, an exotic pest from Asia, was first found in Iowa in 2010 and has now been detected in 61 Iowa counties.
In August of 2014, two emerald ash borer larvae were collected by a homeowner from a residential tree in Story City, making Story County the 13th confirmed infestation at that time.
In the latest detections, insect samples were collected from ash trees in Winthrop (Buchanan County), a rural area east of Randall (Hamilton County), Eldora (Hardin County) and Council Bluffs (Pottawattamie County). The samples were submitted to the USDA’s Animal and Plant Health Inspection Service, which confirmed them positive for EAB. Buchanan and Hardin Counties involved ash trees on private property, whereas Hamilton and Pottawattamie County findings occurred in the right-of-way along I-35 and I-80, respectively.
“June is typically the time of year we receive a surge in phone calls about poorly looking ash trees. We urge people to continue to report suspicious symptoms in counties that are not yet known to be infested,” said Mike Kintner, Iowa Department of Agriculture and Land Stewardship EAB and gypsy moth coordinator. “People can really help minimize the spread of this pest by not giving it a ride in infested firewood between counties or from home to campsite.”
Since the dispersal of this beetle by natural flight is limited to only short distances, people serve as the mode of transportation involving longer distances. Beneath the bark in the larval stage EAB can unknowingly be transported in firewood. Numerous other insects and diseases can also hitchhike in firewood. Iowans are encouraged to use locally sourced firewood, burning it in the same county where it was purchased.
Adult beetles begin to emerge from May to June and can be found throughout the summer months. The metallic-green beetle is slender and approximately 1/2 inch long. After emerging from a tree the beetle leaves behind a telltale D-shaped exit hole approximately 1/8 inch in diameter.
EAB-infested ash trees can include branch dieback in the upper crown, water sprouts along the trunk and main branches, vertical bark splits, D-shaped emergence holes, S-shaped tunneling under loose bark, as well as woodpecker damage. EAB larvae kill ash trees by tunneling under the bark and feeding on the part of the tree that moves nutrients up and down the trunk. Starved trees usually die within 2-4 years.