Pest description and crop damage Small, dull green aphid causes extreme needle drop. Aphid appear early in the season (about February) and may increase rapidly during March and April.
See "Spruce" in:
Early-season control is the key to successful treatment. Usually by the time damage is noted, it is too late for effective treatment. It is important to cover foliage thoroughly, including lower leaf surfaces.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press(p. 82).