Large Wasp-Like Insect on Silver Maple: Clearwing Borer

A 2.5–3 inch wasp-like insect with long tail on silver maple, plus bore holes in dead trunk, is a clearwing borer (likely maple callus borer, Synanthedon acerni). These are day-flying moths that mimic wasps; they don't sting.

Control

• Prevent: keep tree vigorous, irrigate during drought.
• Treat: trunk spray with Onyx or Merit (permethrin/esfenvalerate) now and again in spring to catch egg-laying adults.
• Timing matters: spray when adults are active.

See: entomology.umn.edu/cues/Web/088ClearwingBorers.pdf