Author: Scott M. Salom, Virginia Polytechnic Institute and State University

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Superorder	Holometabola
Order	Hymenoptera
Superfamily	Tenthredinoidea
Family	Diprionidae
Subfamily	Diprioninae
Genus	Neodiprion

Scientific Name

Neodiprion excitans

Common Name

blackheaded pine sawfly

Distribution and Hosts

The blackheaded pine sawfly Neodiprion excitans 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.

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.

Importance

This sawfly, which ranges from Virginia to Texas, prefers loblolly and shortleaf pines but also feeds on slash, longleaf, and pond pines. Because heaviest defoliation occurs during late summer and fall, trees may go through the winter stripped of their needles. The resulting loss in vigor may predispose slow-growing pines to bark beetle attack.

Identifying the Insect

Older larvae are about 1 inch (25 mm) long and olive green with a glossy black head. Two longitudinal black stripes run along the top of the body, and a conspicuous row of black spots occurs on each side. The adult female is about 1/2 inch (12 mm) long with a light brown body. She lays her eggs singly at the bases of needles on the tips of shoots.

Identifying the Injury

Defoliation during spring and summer is not serious because larvae tend to feed on the older foliage. In the fall, however, defoliation may exceed 90 percent of the total crown and result in a considerable growth reduction during the following season. Heavily defoliated trees, especially overmature sawtimber, may be killed following secondary attacks by bark beetles.

Biology

The larvae overwinter in light brown cocoons spun principally in duff, topsoil, and bark crevices at the base of the trees. Pupation is completed in the spring, and both adults and larvae are sometimes present throughout the summer and fall. There are 3 to 4 generations per year in the Gulf coastal region Control - Outbreaks of the blackheaded pine sawfly occur periodically and usually subside rapidly. Natural enemies are usually helpful in preventing or ending outbreaks. Insecticides may be warranted on high value trees.

Control

Outbreaks of the blackheaded pine sawfly occur periodically and usually subside rapidly. Natural enemies are usually helpful in preventing or ending outbreaks. Insecticides may be warranted on high value trees.

Gallery

References

Insects and Diseases of Trees in the South. 1989. USDA Forest Service - Forest Health Protection. R8-PR16. 98 pp. Taken from http://fhpr8.srs.fs.fed.us/forstpst.html