Forest Health Protection, Southern Region

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.