Pest description and crop damage Green to brown larvae, up to 1 inch long, attack foliage and buds of fir and spruce.
See "Spruce" in:
Christmas Tree Plantation Pests
Chemical Control of Nursery Pests
Apply in spring (May) when larvae feed on old needles and before they enter buds. June to July applications will control larvae on new growth.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 28).