Blackheaded Pine Sawfly
Contact: Eric Day, Manager, Insect Identification Laboratory
Publication 444-236, August 1996
Distribution and Hosts
The blackheaded pine sawfly occurs from Virginia to Florida,
west to Arkansas and Texas. It prefers loblolly and shortleaf
pines, but also feeds on slash, longleaf, and pond pines.
Description of Damage
An important pest in the South that is known to cause
widespread damage in young pine plantations. However, it is not
considered an important pest in Virginia. Defoliation during the
spring and summer is not serious because larvae feed on the older
foliage. In the fall, defoliation may exceed 90 percent of the
total crown, resulting in considerable growth loss for the next
growing season. Defoliation also predisposes trees to bark beetle
attack.
Identification
Sawfly larvae look like caterpillars, yet have more than
five pair of "stub-like" prolegs behind the three pair of true
legs on the insect's abdomen. In contrast, caterpillars never
have more than five prolegs. Older larvae are 25 mm long, and
have glossy black heads and olive green bodies. They have two
longitudinal black stripes on their back, with a row of black
spots on each side, and a large spot on the last abdominal
segment. Mature larvae spin golden-brown cocoons that are 3.2 x
7.5 mm in size. Cocoons can be found in the soil, on twigs, in
bark crevices, and beneath loose bark scales. Adults emerge from
the cocoons and look similar to flies. Note that sawflies have
two pair of wings and true flies only have one pair. Eggs are
deposited at the bases of needles on the tips of shoots. Newly
hatched larvae are similar to older larvae, yet smaller in size.
Life History
In Virginia and North Carolina there are two
generations/year. Eggs overwinter and hatch from early to mid-
April. Larvae feed gregariously for five weeks and cocoons are
formed in mid-May, with adults emerging at the end of May.
Larvae from the second generation emerge in June and form cocoons
during late July to early August. Pre-pupae remain inactive in
the cocoons until late fall. Adults emerge in November and
deposit their eggs.
Control
Since the host plant species are not widespread in Virginia,
there is little need for use of active control strategies. Where
hosts are abundant, outbreaks of the blackheaded pine sawfly
occur periodically and usually subside rapidly. Factors
contributing to the quick decline in sawfly populations are
starvation and natural enemies.
Prepared by S.M. Salom, Department of Entomology, Virginia
Polytechnic Institute and State University, Blacksburg, Virginia,
24061-0319
References
Anonymous. 1989. Insects and Diseases of Trees in the South.
USDA For. Serv. Protection Report R8-PR16.
Doggett, C.A. 1972. Notes on the biology of Neodiprion excitans
in North Carolina. J. Econ. Entomol. 65:701-702.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA For. Serv.
Misc. Publ. #1426. 608 pp.