Dogwood Borer

What it does

Larvae are the damaging stage. They bore into the bark, usually through existing wounds, cracks, or sunscald, and feed in the inner bark and cambium. Their tunneling girdles branches and sections of trunk, disrupting the flow of nutrients and causing dieback above the injury. Because they exploit wounds, trees stressed by drought, transplanting, or mechanical damage are most heavily attacked.

Where it lives

The dogwood borer's main host is flowering dogwood, but it also attacks many other trees, including apple (where it infests burr knots on rootstocks), pecan, oak, birch, willow, and others. It is found in landscapes, orchards, and woodlands across the eastern and central United States, wherever suitable hosts grow. Larvae live under the bark near wounds and grafts.

How it breeds

There is generally one generation per year, with a longer flight period in the South. Adult clearwing moths emerge from late spring into summer and lay eggs near bark wounds and rough areas. Larvae bore in and feed under the bark through the season, overwinter as larvae, and pupate beneath the bark, emerging as moths the following season to continue the cycle.

What it eats

Larvae feed on the inner bark and cambium of dogwood and other host trees, especially around wounds and grafts. The adult moths visit flowers for nectar but do no damage. The insect depends on living host trees, particularly injured ones, to complete development.

Identification

The adult is a small clearwing moth, about a 3/4-inch wingspan, blue-black with yellow bands, mimicking a wasp. It is rarely noticed. The signs on the tree are more telling: sawdust-like frass pushed from small holes in the bark, loose or sloughing bark, and dieback of limbs above the damaged areas. Larvae are cream-colored caterpillars found under the bark.

Signs of an infestation

• Sawdust-like frass extruded from small holes in the bark
• Loose, cracked, or sloughing bark on the trunk and limbs
• Dieback of branches above damaged sections of bark
• Swollen or callused wounds where larvae have tunneled
• Wilting or sparse foliage on affected limbs
• Wasp-like clearwing moths near the tree in early summer

Prevention tips

• Prevent bark wounds from mowers, trimmers, and pruning tools
• Keep dogwoods vigorous with mulch, watering, and proper siting in part shade
• Avoid planting flowering dogwood in hot, exposed, sunscald-prone spots
• Wrap or protect trunks of young or newly planted trees where appropriate
• Prune out and destroy infested, dying wood in fall or winter

Professional solutions

Keeping trees healthy and wound-free is the most effective control, since the borer exploits injuries. A certified arborist or extension office can confirm an infestation and, for valued trees, time bark or systemic insecticide treatments to the adult flight period, when eggs and young larvae are present. Once larvae are deep under the bark, sprays are far less effective, so prevention and good tree care are key.