Dogwood Borer (Synanthedon scitula)
The adults are clearwing moths about 3/8 inch long. They have two gold bands on a bluish-black abdomen. The larva grows to ½ inch long and are white with a brown head and have two reddish-brown spots on the back, near the head. There is one generation a year. Larvae overwinter under bark. Adult emergence peaks around early to mid-May, but occurs continually from April to October because eggs are laid for several months.
Look for brown frass around wounds and bark cracks. Remove loose bark with a knife. Larvae may be found in short tunnels under bark near wounds.
Protect tree trunks with mulch bands to prevent wounds from lawn mowers. An early April application of a long residual insecticide to the bark should prevent infestation. An additional application may be necessary in late May. Kousa dogwood appears resistant to this borer.