Redheaded Pine Sawfly
Contact: Eric Day, Manager, Insect Identification Laboratory
Publication 444-239, August 1996
Redheaded Pine Sawfly
Redheaded Pine Sawfly, Neodiprion lecontei (Fitch)
Distribution and Hosts
The redheaded pine sawfly occurs from S.E. Canada
throughout the eastern U.S. Feeding is primarily restricted
to the two- and three-needled pines, such as Jack, red,
shortleaf, loblolly, slash, longleaf, and pitch pines.
White pine and norway spruce may also be defoliated.
Description of Damage
The redheaded pine sawfly is the most widespread and
destructive of the pine sawflies and is considered an
important pest of ornamental, forest, and especially
plantation trees. It usually feeds on young trees,
preferably 0.3 to 4.6 m tall. Trees growing under stress in
shallow soils, very wet or dry sites, or under stress from
competing vegetation are especially susceptible to
infestation and heavy defoliation. Outbreaks occur
periodically and tend to subside after a few years of heavy
defoliation. Severe outbreaks have resulted in death or
deformity of young pines.
Identification
Sawfly adults look similar to true flies , yet have two
pair of wings instead of one pair. Adult females are 6 to
9.5 mm in length while males are 5 to 6.5 mm. Except for
legs and wings, males are completely black and females are
predominantly black with the underside of their abdomen
being whitish.
Eggs are oval, 0.5 mm long and 0.25 mm wide. They are
laid individually in a row of slits cut into the edge of the
needles. All eggs laid by a female are generally grouped on
needles of a single twig.
Sawfly larvae resemble caterpillars, yet have at least
six pair of "stublike" prolegs behind the three pair of true
legs on the insect's abdomen. In contrast, caterpillars
never have more than five pair of prolegs. Larvae emerge
from eggs 2 to 5 mm long. After feeding, the larval body
develops black spots and the head capsule becomes orange-
red. In the fourth and fifth instars, black spots surround
the eyes. At this stage, the body is deep-yellow.
Larvae spin cocoons to overwinter and pupate in. The
cocoons are red-brown, cylindrical with rounded ends, and
are 10 mm long for females and 7.5 mm long for male.
Life History
In Virginia, there are two to three generations/year.
The redheaded pine sawfly overwinters in the prepupal stage
in its cocoon spun in the litter of the soil beneath the
infested trees. Pupation occurs soon after the onset of
spring warm weather, and adults emerge in a few weeks. Eggs
deposited in the needles hatch in 3 to 5 weeks. Larvae feed
gregariously on new and old needles and also on the tender
bark of young twigs. In Virginia, larvae begin spinning
cocoons in late June, early July. Second generation adults
emerge in July and August. Larvae feed through September
and then spin their cocoons. In warmer areas, adults will
emerge at the end of September to late October and lay eggs
for a third generation that remains active into December.
Control
Numerous natural control agents play important roles in
keeping redheaded pine sawfly populations down. Outbreaks
often collapse from rodents feeding on the pupae and
diseases killing the larvae. Of the 58 species of parasitic
and predatory insects affecting this pest, the native egg
parasite Closterocerus cinctipennis Ashmead (Hymenoptera)
and the larval parasite Spathimeigenia spp. (Diptera) are
the most important.
Silvicultural practices recommended for preventing
redheaded pine sawfly outbreaks include: 1. remove
competing vegetation before planting pines; 2. avoid
planting pines in high hazard areas such as frost pockets,
or on excessively dry, wet, or nutrient deficient soils; and
3. promote early closure of pines to prevent competing
vegetation such as weeds or hardwoods.
When deemed necessary, chemical treatments can be used
as an effective control. In addition to synthetic
insecticides, Bacillus thuringiensis, a bacterium, is an
effective naturally occurring organism in a spray
formulation registered for use against this pest in
Virginia. Consult the most recent Pest Management Guide for
horticultural and forest crops, Virginia Cooperative
Extension Publication 456-017, for a listing of the
currently registered chemicals and formulations.
Prepared by S.M. Salom, Department of Entomology, Virginia
Polytechnic Institute and State University, Blacksburg,
Virginia, 24061-0319
References
Benjamin, D.M. 1955. The biology and ecology of the
redheaded pine sawfly. USDA For. Serv. Tech. Bull. No.
1118. 57 pp.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA For.
Serv. Misc. Publ. #1426. 608 pp.
