The pitch mass borer is a native clearwing moth in the genus Synanthedon whose larvae feed within various pines and spruce. Feeding by the larvae (caterpillars) of this insect causes pitch masses to form on host plants. Two or three years are required for this insect to complete its life cycle, with adult moths present during the summer. Adult pitch mass borer moths may resemble wasps. Adult males and females are blue/black from above, marked with a patch of red/orange on the underside of the abdomen, with some orange on the top of the fourth abdominal segment. Orange is also found along the sides of the abdomen. Forewings are black/blue in color and opaque with wing length of 0.47 to 0.59 inches. Adults are said to emerge, mate, and females lay eggs on their hosts some time in July. By the late summer, the larvae (immatures; caterpillars) bore into their host plant, tunneling through the trunks, often directly beneath a branch. Larvae have uniformly dark brown heads, white bodies, and prolegs with rows of 6-8 crochets on the bottom of their "feet". At the site of the borer wound, large amounts of pitch exude from the tree in a hemispherical mass above the larval tunnels. Larvae continue to feed and develop in the tree through the following year, and it is thought that caterpillars may take up to two years to mature. Masses may be 3-4 inches in diameter. Pupation occurs in a subsequent end of May through June in time for adult emergence by July and August. Pupal cells are formed within the pitch mass and lined with silk (Beuttenmüller, 1901). Pupae are 0.73 inches long and light brown in color (Kellicott, 1881).
The pitch mass borer is a clear winged moth common to conifers in New England and beyond. Adult moths active during the summer. Following egg laying and egg hatch, the larvae tunnel under the bark to the cambium. Obvious, large globs of pitch appear on trunks. Occurs sporadically on individual trees. Host trees with active caterpillars have pitch masses that may appear coated in a white, powdery substance. Larvae may also preferentially bore into the host beneath a broken branch or scar. This insect will attack large trees, up to 30-40 feet from the ground. Healthy trees are also preferentially utilized. Overall damage to the health of the host tree is typically not extensive, and therefore chemical management of this insect is often unnecessary.
Taft et al., 1991 notes that male pitch mass borers strongly respond to an artificial sex pheromone attractant. However, historically, some records note that adults are difficult to collect, and are rarely even available as museum specimens. ZZOH/EZOH in a ratio of 50:50 is reported as the highly attractive pheromone blend, however it may not be readily commercially available.
Pitch can be removed and the single larva within destroyed. Physical/mechanical management of this insect, if it can be safely done, is a great way to manage the pitch mass borer on individual specimen trees. The act of just pulling the caterpillar from its pitch mass will kill it - much to the frustration of history's entomologists looking to study them - as soon as contact of the pitch is made with the caterpillar's body and hardens and adheres to them.
Parasitism by natural enemies is reported to be relatively common. Parasitic wasps in the family Eulophidae are noted but not specified, as well as a caterpillar-eating species of fly (Engelhardt, 1946).
Acephate (NL)
Bifenthrin (larvae) (NL)
Chlorantraniliprole (NL)
Cyantraniliprole (NL)
Emamectin benzoate (L)
Permethrin (L)
Chemical management of the pitch mass borer is often unnecessary. This native insect typically does not cause significant damage to the overall health of its host plants.
Active ingredients that may be applied systemically include: Acephate (injection), chlorantraniliprole (soil drench), cyantraniliprole (soil drench, soil injection), and emamectin benzoate (injection).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.