This article was published originally on 6/7/2013
Ash trees decline for a variety of reasons, and not just because of the emerald ash borer.
Reminder: Emerald ash borer has only been found in Allamakee County in Iowa. See the Emerald Ash Borer Team news release for January 17, 2013.
Declining, dying or recently-killed and cut ash trees will be infested by a variety of native borers. The most common is the flatheaded appletree borer (Chrysobothris femorata) that attacks a wide variety of hardwood trees. The larvae create galleries of scooped-out tunnels and chambers just under the bark. See photo below.
Ash bark beetle larvae are about one-eighth inch long and feed between the bark and the wood creating a feather-like pattern of parallel tunnels.
Spray treatments for these borers are not practical. Maintaining tree health and vigor is our best management option.
These and other common problems of ash are described in ISU Extension & Outreach pamphlet SUL 0021, "Common Problems of Ash Trees," available online at the ISU Extension Online Store.
Flatheaded appletree borer damage - below - and ash bark beetle tunnels - above.