Neodiprion tsugae (Diprionidae)

the hemlock sawfly

Adults:

Yellow brown in colour with dark brown antennae. They possess two pairs of wings. Males have conspicuous feathery antennae, whereas the female antennae are inconspicuous and thread-like.

Larvae:

Greenish with longitudinal stripes - head black. Prolegs occur on abdominal segments 2, 3, 4, 5, 6, 7, 8 and 10, none on 1 and 9.

Damage:

Eggs are deposited in small slits cut by female along the underside of the edge of the top half of current year's needles. Usually only one egg is laid per needle. Young larvae are gregarious and always feed in groups, principally on older needles. Cocoons may be formed on the tree but most are formed in the duff beneath the defoliated tree. Heavy defoliation causes trees to appear grey or greyish-brown and tree crowns to appear thin.

Principal Hosts:

Western hemlock (Tsuga heterophylla), occasionally Tsuga mertsiana and Abies amabilis.

Economic Importance:

Since larval feeding occurs on older needles, feeding tends to reduce growth rather than kill trees outright. Extensive outbreaks on western hemlock have been recorded in western North America.

References and Links:

EAG: 476-479; FC: 444.

See JP17.