• Reardon, Richard C.
  United States Department of Agriculture, Forest Service, Cooperative State Research Service, Agriculture Handbook, No. 625
  

Damage caused by western spruce budworm larvae can be minimized with chemical insecticides. Insecticides are aerially applied to suppress infestations over large areas; ground-operated equipment, implantation, and injection were not designed to replace ground or aerially operated spray equipment but to provide a portable, closed system that would minimize loss of insecticide and can be used in any weather, in remote or hard to reach places, and where adjacent areas might be sensitive to contamination (for example, residential zones, urban parks, and campgrounds). In both methods, the insecticide is carried in the sap to the buds and needles, which then become toxic to the larvae feeding on them.