Introduced Pine Sawfly
Egg-When first laid, the egg is pale bluish white and about 1.5 mm long. It has straight sides and blunt, rounded ends. Before hatching, the egg becomes slightly enlarged and turns dark green
Larva-Less than 3 mm long when newly hatched, the young larva is dull gray with black legs. The larva undergoes subtle color changes as it matures and eventually becomes dark gray or black with white and yellow spots, a shiny black head, and a dark, double stripe down its back. A fully grown larva may be as long as 25 mm.
Cocoon-The pupa is enclosed within a dark-brown cocoon 7 to 9 mm long and 3.5 to 4 mm wide. The cocoon of a female sawfly is slightly larger than that of a male sawfly.
Host Plants -Five-needled pines and soft, two-needled pines are the preferred hosts of this pest. White pine is particularly subject to infestation; Scotch, red, jack, and Austrian pines are also commonly injured.
Damage Sawfly larvae damage conifers by defoliation. Ragged, shredded edges on the outer tips of needles are the first sign of infestation. Young larvae are responsible for this type of injury. Older larvae consume entire needles and nibble at the bark. If heavy defoliation occurs late in the season after bud formation, branches or entire trees may be killed. Those trees or shrubs that survive infestation often lose much of their top growth.
Life History -Studies of the biology of the introduced pine sawfly in the southern Appalachians are just beginning. Therefore, little is known concerning its life history in North Carolina. The following information is based on life history studies in the more established areas of its range.
Introduced pine sawflies overwinter as prepupae inside cocoons usually hidden among ground litter. First generation adults appear from April to June, the first eggs being laid around mid-May. Depositing an average of 70 eggs, females insert about 10 eggs in a row into single pine needles. Ten to 14 days later, larvae hatch from the eggs and feed on conifers. In late July, larvae begin spinning cocoons among needles, in bark crevices, or at the base of small branches.
Second-generation sawflies first appear in early August. Seven or 8 days after eggs are laid, larvae hatch and feed until September. Cocoons are then spun on trees or among soil litter. Some of these cocoons overwinter, but adult sawflies emerge from others and produce a partial third generation in late fall. However, most of these late larvae, as well as prepupae in cocoons on trees, are killed by low winter temperatures. Cocoons among soil litter have the best chance of surviving the winter.
Parasites, predators, and low winter temperatures kill well over half of the overwintering sawfly population; yet heavy infestation inevitably recur. The treatment of large areas of trees is not practical, but small, localized infestations can be controlled. Pesticides are available for applications to infested yard trees, shurbs, or nursery stock. Since generations overlap and all life stages may be present at once, rpeated pesticide applications may be necessary to control new sawfly larvae as the emerge. For specific chemical controls, see the current state extension service recommendations.