The redheaded pine sawfly did not become an important pest until
extensive planting of pine in pure plantations began in the 1920’s.
Since then, outbreaks in young natural pine stands and plantations have
been common in the South, the north-central states, and eastern states.
Feeding is primarily restricted to the two- and three-needled pines
under fifteen feet in height. Shortleaf, loblolly, longleaf, and slash
are the species most commonly attacked in the southern states.
[Illustration: Redheaded pine sawfly larva.]
In the fall, sawfly larvae drop to the ground, spin cocoons in the duff
or topsoil, and overwinter as prepupae in a small, brown cocoon. With
the coming of spring, pupation occurs and adult emergence follows in
about two weeks. Some prepupae may remain in a resting stage for more
than one season before emerging. Each female lays about 120 eggs. She
cuts a small slit in the edge of a needle and deposits a single egg
inside each slit. Eggs laid by a single female are generally clustered
on the needles of a single twig. Eggs hatch in three to five weeks,
depending on temperature and locality. Larvae feed gregariously on the
host for 25 to 30 days. When fully grown, larvae drop to the ground and
spin their cocoons. In the South there are at least two generations per
year with a maximum of five being recorded. Colonies of different ages
may co-exist in the late fall or early winter.
Outbreaks occur periodically and tend to subside after a few years of
heavy defoliation. Numerous parasitic and predatory insects play an
important role in causing the decline of infestations, as do adverse
weather conditions during the larval stage. When deemed necessary,
chemical treatment is an effective control.