Larvae of the Zimmerman pine moth damage trees by tunneling under the bark, making gouging wounds.
Most injuries occur at branch crotches.
Pale yellow, popcorn-like masses of sap occur at wounds. Broken branches caused by Zimmerman pine moth. Popcorn-like pitch masses from Zimmerman pine moth. In recent years, the Zimmerman pine moth, Dioryctria zimmermani , has become established along the Front Range. Austrian pines have been most commonly infested.