Hand release of 22 5-year-old white spruce, Picea glauca (Moench) Voss, dramatically increased the amount of defoliation by the yellowheaded spruce sawfly, Pikonema alaskens is . The percent defoliation of the released trees was six times the defoliation in the control trees. A light overstory for young white spruce is suggested as a silvicultural method of reducing defoliation by this sawfly.
Morse, B. W. and Kulman, H. M.
"Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae),"
The Great Lakes Entomologist: Vol. 17
, Article 11.
Available at: http://scholar.valpo.edu/tgle/vol17/iss4/11