Conifer sawfly / Hemlock sawfly, Neodiprion spp.
 

Fig. 18   Mortality of western hemlock caused by conifer sawfly.	Fig. 19  Larvae of conifer sawfly.	Fig. 20   Older foliage is preferred

Distribution:  Coastal and interior wet belt areas of  B.C. 

Tree Species Attacked: Western hemlock and amabilis fir are most frequently attacked, but Sitka spruce may also be damaged. All ages are susceptible.

Insect Description & Damage Symptoms: Larvae are present from June to August. Newly emerged larvae are almost black, with a shiny black head. Mature larvae are 1.5 to 2.0 cm long and are green or yellow-green, with a broad medium-dark band on each side and a narrower, darker band below that. The head remains dark. Larvae are wasteful feeders of older foliage; current foliage may be eaten under starvation conditions. Larvae often feed in colonies, especially when young. When disturbed, larvae will hold on with hind legs and flick the front of the body. Cocoons are formed during July and early August and are commonly found in the lower crown under twigs or needles or on understory vegetation. They are 0.5 to 1.0 cm long, cylindrical, have rounded ends, vary from light grey to brown in colour, and are tough and papery. 

Damage: Conifer sawfly usually affects older foliage only. Therefore, mortality is not common but some top-kill and radial growth loss may occur. The potential for mortality is greatly increased by repeated defoliation, or when conifer sawfly occurs with defoliators that prefer current foliage, such as western blackheaded budworm. Conifer sawfly damage may predispose trees to secondary attacks by other insects or fungi. Outbreaks are usually short-lived. 

Similar Damage: Western hemlock looper defoliation may be confused with conifer sawfly damage, but the larvae are easily distinguished from each other.

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BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated March 04, 2002