Flowering dogwoods are a favorite in yards around Bloomingdale, so it's frustrating when one starts losing branches for no clear reason. Dogwood borers are one possible cause. These insects tunnel under the bark, out of sight, and they're especially drawn to trees that have been wounded. Below, we'll cover what dogwood borers are, the signs of damage, what makes trees vulnerable and what you can do to protect them. If you're seeing insects or damage you can't identify, our pest inspection services can help you figure out what's going on.
What Dogwood Borers Are
The dogwood borer is a small clearwing moth native to eastern North America. The adults are active in late spring and summer. They're dark blue-black with yellow bands and partly clear wings, which makes them look a lot like small wasps. They don't sting and don't harm trees directly.
The problem is the larvae. Females lay eggs on the bark, usually near wounds, rough patches or cracks. The caterpillars that hatch are pale with brown heads. They bore into the bark and feed on the living layer just beneath it, often for most of a year, before turning into adult moths.
Why Dogwoods Get Infested
Dogwood borer larvae have trouble getting through smooth, healthy bark. They look for an easier way in. Common entry points include:
- Mower and trimmer wounds. Nicks at the base of the trunk from lawn equipment are a frequent starting point.
- Pruning cuts and broken branches. Open wounds that haven't healed.
- Cracked bark. Bark damaged by cold, sun or stress.
- Graft unions and burr knots. Rough, swollen areas on the trunk.
Trees stressed by drought, poor planting or too much sun also tend to have more trouble. Dogwoods generally prefer partial shade and moist, well-drained soil. The insect also attacks some other trees, including apple trees, especially at burr knots near the base.
Signs Of Dogwood Borer Damage
- Rust-colored frass. Fine, reddish-brown, sawdust-like material on the bark or at the base of the trunk.
- Loose or sloughing bark. Patches of bark that lift away or look sunken and dead.
- Wet or stained areas. Damp-looking bark near a wound.
- Branch dieback. Leaves that wilt, turn red early or drop, and branches that die back from the tips.
- Pupal skins. Small, empty brown casings sticking out of the bark in summer after the moths emerge.
Repeated infestations over several years can girdle branches or the trunk and kill the tree. Young trees are especially at risk.
Because the larvae feed out of sight, damage often builds for more than one season before anyone notices. A slow decline that starts on one side of the tree, or above one old wound, is a good reason to take a closer look at the bark below it. Dogwood borers stay in living trees and don't move into the wood of your house, so this is a yard concern rather than a structural one.
How To Tell It Apart From Other Problems
Dogwoods can decline for other reasons, including leaf diseases, root problems and drought stress. Borer damage is usually tied to a specific wound or rough area on the trunk or a large branch, with frass close by. Leaf spots and blotches across the canopy point more toward disease. If the holes and damage you're seeing are on ash trees, read our guide to emerald ash borer signs instead, because that's a different insect with a different response.
How To Protect Your Dogwoods
- Keep equipment away from the trunk. A mulch ring around the base keeps mowers and trimmers at a distance. Keep mulch pulled back from the bark itself.
- Water during dry spells. Healthy, well-watered trees resist borers better.
- Prune at the right time. Ask an arborist about the best time to prune, since fresh wounds during the moths' active season can attract egg-laying females.
- Check the trunk each season. Look for frass, loose bark and wet spots, especially around old wounds.
- Remove badly damaged wood. Dead branches and heavily infested wood can be removed by a tree professional.
- Plant in the right spot. When planting new dogwoods, choose a location with partial shade and good drainage.
When To Call A Professional
If a dogwood is losing branches or you're finding frass on the trunk, a certified arborist or your county extension office can confirm the cause and recommend treatment. EcoFusion doesn't treat or inject trees. Where we help is identifying the insects around your home and yard and making sure nothing is heading indoors. Our NJ DEP-licensed technicians can inspect your property and recommend the right next step. We offer free inspections with same-day and next-day service.
A few easy habits, like keeping mowers away from the trunk and watering during droughts, can keep dogwood borers from getting a start. Your dogwoods are worth that small effort, and they'll keep brightening your Bloomingdale yard for years.