The following is information on the Flatheaded Appletree Borer, a pest of many tree species in Delaware
Flatheaded Appletree Borer, Chrysobothris femorata
Flatheaded apple tree borer adults are dark greenish brown on top (dorsal) and brown on the underside (ventral). The wings have two wavy, indented light bands. Look for the adults in sunny locations. You may find adults in the early morning sitting on the bark of a tree. The adults tend to attack stressed apple, beech, dogwood, elm, linden, oak, willows and apple trees. The last two years of drought has stressed many trees in Delaware making them susceptible to attack from this borer. Young, newly transplanted trees can be attacked and killed by this beetle.
Non-chemical Control: Keep trees healthy and vigorous and this beetle will not be a problem. It is easy to say and hard to do in a lot of situations.
Chemical Control: Apply Onyx or Astro to the main trunk of the tree.
Photo of flatheaded apple tree borer by Joseph Berger, Bugwood.org
Information adapted from the current edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.