The Virginia pine sawfly is found from Maryland to North Carolina, and
west to Illinois. The insect prefers Virginia and shortleaf pine, but it
will also oviposit and feed on pitch and loblolly pine.
[Illustration: Virginia pine sawfly larva.]
On warm sunny days in late October and early November, the adult
sawflies emerge from their cocoons in the litter, mate, and the females
lay eggs. The female is equipped with a saw-like ovipositor with which
she cuts a slit at the edge of a needle and inserts a small, white, oval
egg. Several eggs are usually laid at evenly spaced intervals in each
needle, but in only one needle per fascicle. From 30 to 100 eggs are
deposited in this manner by each female. The eggs hatch the following
April and the young larvae feed gregariously on the old needles. Larval
development is usually completed by the time the new needles come out,
giving heavily defoliated trees a tufted appearance. Mature larvae crawl
to the ground and spin cocoons in the litter or surface soil. They
remain as prepupae until late September when pupation occurs.
[Illustration: Pine defoliated by the Virginia pine sawfly.]
Heavy defoliation for two or more years can weaken trees and make them
more susceptible to other insects and diseases, particularly when
associated with drought. In commercial stands the growth loss caused by
several years of 50% defoliation by this insect can amount to ⅓ of the
expected growth.
Several parasites, predators, and a virus attack the Virginia pine
sawfly, but weather conditions seem to be primarily responsible for the
drastic fluctuations in sawfly populations. Several chemicals have
proven effective in preventing damage to ornamentals.