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. A bacterial spray known as Bt (Bacillus thuringiensis) may also provide effective control against yellowheaded sawfly without harming other beneficial predatory insects.

Photos:
spruce_sawfly_damage
spruce_sawfly_larvae


Relevant web sites:
www-ag.usask.ca/cofa/departments/hort/hortinfo/pests/yellow.html
www.pfc.forestry.ca/entomology/defoliators/tenthredinid/yellowheaded_e.html

Other references:
Johnson, W.T. and Lyon, H.H. 1988. Insects that Feed on Trees and Shrubs. Second Edition. Comstock Publishing Associates, Cornell University, Ithaca, NY. 556 pages.

Ives, W.G.H., and Wong, H.R. 1988. Tree and Shrub Insects of the Prairie Provinces. Information Report NOR-X-292, Northern Forestry Centre, Edmonton, AB. 327 pages.

Philip, H. and Mengersen, E. 1989. Insect Pests on the Prairies. University of Albeta, Faculty of Extension, Corbett Hall, Edmonton, AB. T6G 2G4. 122 pages.