CARPENTERWORM, Prionoxystus robiniae (Peck)
The carpenterworm bores in the wood of living hardwood trees, causing costly damage to commercial timber species. In the South, oak species are preferred hosts but black locust, maples, willows, and fruit trees are also attacked. The carpenterworm is distributed throughout the United States.
Carpenterworm adults.
Adult moths emerge in late April to early June, mate, and the females lay groups of eggs in bark crevices or wounds. Each female lays 200 to 500 eggs during her one-week life span. After hatching, the larvae wander over the bark for a short time before boring into the inner bark where they feed until half-grown. The larvae then bore into the sapwood and heartwood, returning occasionally to feed in the inner bark. The larval period lasts from two to four years. Pupation usually occurs deep within the heartwood. Just prior to emergence, the pupa wiggles to the entrance hole where it remains slightly protruding until the adult moth emerges. The large winding tunnels constructed by the larvae in the sapwood and heartwood of living hardwoods serve as an entrance for wood-rotting fungi and insects such as the carpenter ant. In extreme cases, the tree may be structurally weakened and subject to wind breakage.
Carpenterworm galleries in nuttall oak.
Some chemicals which have a fumigating action have proved effective in controlling this insect in shade trees, but no practical control has yet been found for forest trees.
PINE WEBWORM, Tetralopha robustela (Zell.)
Ugly, compact masses of brown excrement or frass pellets around the stem of pine seedlings mark infestations of the pine webworm. Rarely is the defoliation severe enough to kill the seedlings, but it undoubtedly has an impact on growth. Found throughout the eastern United States, the webworm commonly attacks red, white, jack, loblolly, shortleaf, and slash pines.