Red pine sawfly

Distribution

Alberta, British Columbia, Manitoba, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan

This species occurs in jack pine stands along the Fort Nelson River in northeastern British Columbia; it also in eastern Canada to Nova Scotia and south from the New England states to Pennsylvania.

Damage, symptoms and biology

The red pine sawfly feeds mostly on old foliage but will eat new needles after the old foliage has been consumed. Complete defoliation of both the old and new needles of pine will usually kill the tree. Trees that are severely attacked, but not completely stripped, may not be killed outright but frequently die later from attacks of secondary insects or diseases; those trees that survive are usually stunted or become poorly shaped. The insect is chiefly a pest of plantations but it may also cause injury to isolated trees and ornamentals. Outbreaks have not been recorded in British Columbia.

Mature larva up to 25 mm long. Head, black. Body, green to grey, light green middorsal stripe bordered with darker green subdorsal stripes; thin yellow spiracular stripe bordered by green supraspiracular stripe and light yellowish green subspiracular stripe. A dark band extends from the first to the eighth abdominal segment at the base of the prolegs. Prepupal larvae similarly marked except brown. Eight pairs of abdominal prolegs. The adult is a brownish, heavy-bodied, four-winged fly.

This species overwinters in the egg stage. Larvae feed on foliage of the previous year or older from late May to mid-July. The larvae feed in groups or colonies on old foliage, usually devouring all the needles on one branch before migrating to another. They complete four or five instars in 4 to 6 weeks, mature larvae drop to the ground and spin cocoons in the duff near the base of the host tree. A variable percentage of larvae may diapause in the cocoons for 2 or more years. In late summer, the larvae become pupae within the cocoons. Adults emerge from September to October and lay eggs in slits along the margin of a needle.

Other information

Other Neodiprion species appear similar but feed on different hosts.