The dogwood borer, Synanthedon scitula , one of about seven borers that attack dogwoods, is the most serious. It also attacks flowering cherry, chestnut, apple, mountain-ash, hickory, pecan, willow, birch, bayberry, oak, hazel, myrtle, and loquat. Wounded trees are the most vulnerable since the larvae must gain access to the tree through wounds or scars. The adult is a clearwing moth which looks like a wasp. An early symptom is the sloughing of loose bark.
More advanced symptoms are crown dieback and adventitious growth.
Course sawdust-like frass may be present at the entrance holes and pupal skins at the exit holes. Small wet areas on the bark in early summer may indicate young borer activity. It has a blue-black body with yellow bands and clear wings. It generally begins to emerge when the last of the flower petals are ready to drop and the weigela begins to bloom at the end of April or early May and continues into September. The females lay eggs on or near wounds or in the crotches of limbs.