Sycamore Borer Damage: Identification and Treatment

Question: Mature sycamore in central NM shows bark shedding, dark frass, and silk-like balls on trunk. Pine bark beetles are common here—is there a sycamore equivalent? Can the tree be saved?

Answer

This is sycamore borer (Synanthedon resplendens), a clearwing moth—not a beetle. Larvae tunnel under bark, producing frass and weakening the tree. Heavy infestations cause girdling and dieback.

Management

• Spray trunk with Merit (imidacloprid) or Onyx (bifenthrin) where damage is active; these penetrate bark and kill larvae.
• Fertilize with 10-10-10 at 1 lb per inch trunk diameter to boost vigor and resistance.
• Probe tunnels with a fine wire to mechanically kill larvae, or inject beneficial nematodes.
• Prevent wounds—borers target stressed or injured trees.

With treatment and improved care, the tree can recover.