Yellowheaded Spruce Sawfly

Problem type: Insect

Name of problem: Yellowheaded Spruce Sawfly

Plant name(s): Engelmann, Norway, Sitka, Colorado blue, white, red and black spruce

Symptoms / Characteristics:
The yellowheaded spruce sawfly, Pikonema alaskensis, is a pest of both ornamental and shelterbelt spruce plantings. Damage is attributed to caterpillar-like larvae that consume the younger needles first before moving on to older foliage. Affected branches may appear completely stripped and damage usually, but not always, begins at the top of the tree. Infestations have a negative impact on both appearance and growth. Repeated attacks may eventually result in tree death.

The larvae are initially yellowish in colour with brown heads. At maturity, they are dark green with pairs of longitudinal greyish- green stripes and reddish-brown heads. Damage is likely to occur from mid June to July after which time the mature larvae drop to the ground in preparation for winter.

Control / Preventions:
Control measures should commence in mid-June with regular scouting for damage symptoms or feeding larvae. In areas with low infestation, isolated colonies may be removed with light pruning or a high pressure water spray. Larvae should then be destroyed in order to prevent reinfestation. In areas of high infestation, mix a teaspoon of dish soap into a gallon of water and apply as a high pressure spray for effective non-chemical control. Commercial sprays containing permethrin, carbaryl or malathion are effective but must be applied according to manufacturer instruction and precaution.