Blackheaded Pine Sawfly
Neodiprion excitans Rohwer

This sawfly, which ranges from West 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.

Identification:

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.

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 and History:

Two generations occur each 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.