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.
[Illustration: 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.
[Illustration: 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.