Which pest leaves a small D-shaped exit hole where adults emerge from the trunk and branches?

Which pest leaves a small D-shaped exit hole where adults emerge from the trunk and branches?

• A. Bronze birch borer
• B. Emerald ash borer
• C. Asian longhorned beetle
• D. Mountain pine beetle

Answer: (A)

Flatheaded borers leave exit holes that are distinctly D-shaped as the adult beetle cuts out through the bark. Bronze birch borer is a classic example in ornamental trees and is well known for producing small D-shaped exit holes in the trunk and on branches when adults emerge. That specific hole form is the best clue, especially for a birch host. By contrast, Asian longhorned beetle tends to leave larger, rounder holes, mountain pine beetle produces tiny pinhole-type exits in pine bark, and emerald ash borer, while also a flatheaded borer, is associated with ash and the context here points most directly to bronze birch borer.

Flatheaded borers leave exit holes that are distinctly D-shaped as the adult beetle cuts out through the bark. Bronze birch borer is a classic example in ornamental trees and is well known for producing small D-shaped exit holes in the trunk and on branches when adults emerge. That specific hole form is the best clue, especially for a birch host. By contrast, Asian longhorned beetle tends to leave larger, rounder holes, mountain pine beetle produces tiny pinhole-type exits in pine bark, and emerald ash borer, while also a flatheaded borer, is associated with ash and the context here points most directly to bronze birch borer.