Carpenter Ants in Trees: When to Worry and How to Control Them

Understanding Carpenter Ant Colonies in Silver Maples

Carpenter ants nesting in a silver maple often alarm homeowners, but they are not the cause of tree decline. They exploit existing decay.

Why They’re There

• Nest in rotted, decayed wood or the central heartwood (non-living core).
• Enter through knots, cracks, old borer tunnels, or storm wounds.
• Underlying causes: drought, disease, insects, or mechanical injury that killed limbs and allowed wood rot to set in.

When Control Is Needed

Only if ants are entering the home from the tree colony. Otherwise, they’re a symptom, not a threat to tree health.

Effective Control Methods

Baiting (Best for Hidden Nests)

• Use commercial baits (Terro, or products with hydramethylnon, sulfluramid, abamectin, or boric acid).
• Ants carry bait back to the colony, eliminating it over days to weeks.
• Homemade option: 1% boric acid in 10% sugar water—slow but inexpensive.

Direct Nest Treatment (If Exposed)

• Spray aerosol or liquid insecticide (bifenthrin, cyfluthrin, deltamethrin, permethrin) directly into the cavity.
• Act quickly—disturbed colonies relocate rapidly.

Long-Term Tree Health

Address the root cause of decay: improve watering, fertilize if needed, and prevent wounding. A vigorous tree compartmentalizes decay and resists further colonization.