Pest profile

Pitch Mass Borer

Synanthedon pini · Lepidoptera: Sesiidae[3]

The pitch mass borer is a native, wasp-like clearwing moth whose larvae tunnel into the trunks of pines and spruces, causing large masses of pitch (sap) to form at the wound.[1][2]

Pitch mass borer moth, a blue-black clearwing moth with orange on its abdomen, resting on pitch
Pitch mass borer moth, a blue-black clearwing moth with orange on its abdomen, resting on pitch. Photo: Sigrid Jakob, public domain (CC0), via iNaturalist

How to identify it

  • Adults resemble wasps: blue-black above with red-orange on the underside and sides of the abdomen and dark, opaque forewings.[1][2]
  • Larvae are white with dark brown heads and tunnel into the trunk, often right beneath a branch.[2]
  • The main sign is a mass of pitch oozing from pits or holes in the bark.[1][2]

Look-alikes

Look-alikeHow to tell them apart
Western pitch mothsPitch moths are all clearwing moths in the genus Synanthedon whose larvae make sap-oozing holes in conifers.[1]

Where it lives

Illinois and UMass Extension both report it on landscape pines and spruces.[1][2]

US map: public records from 9 states since 1990 (GBIF).

Biology and life cycle

Adults are seen only in summer; females lay single eggs on the bark around July.[1][2]

By late summer the larvae bore into the trunk, and the life cycle takes two to three years.[1][2]

Damage and signs

  • Hosts include Austrian, eastern white, Scots, jack and mugo pines and white, Norway and Colorado blue spruce.[1][2]

Health risk

None to people or pets.[1][2]

Control

When to call a professional

Check with your state's land-grant university Extension service for current treatment recommendations.[1]

Common questions

What are the globs of sap on my pine trunk?
Pitch masses from pitch mass borer larvae tunneling into the trunk are one cause.[1][2]
Is the wasp-like insect on my pine a wasp?
It may be a pitch mass borer moth; adults resemble wasps.[1][2]
How long does a pitch mass borer live in the tree?
Two to three years to complete its life cycle.[1][2]

Sources

  1. University of Illinois Extension, “Pitch Mass Borer.” extension.illinois.edu/insects/pitch-mass-borer (accessed 2026-10-15)
  2. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Synanthedon pini (Pitch Mass Borer).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/synanthedon-pini (accessed 2026-10-15)
  3. iNaturalist, “Synanthedon pini taxon page (order and family).” www.inaturalist.org/taxa/232122 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.