Forest Pests: Insects, Diseases & Other Damage Agents

Spruce Budworm (Choristoneura fumiferana)

Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p.

Description. Mostly greenish gray body with distinct, pale subdorsal spots; variable color on head and prothoracic shield. Dark brown head; yellowish brown prothoracic shield with various dark marks and with greenish gray anterior margin. Greenish gray of upper two-thirds of body contrasts with greenish yellow of lower one-third. Pair of offset, yellowish white subdorsal spots on most segments; single pale spot above and below each abdominal spiracle. Prolegs on A3 to A6 reduced in size, but those on A10 of normal size; yellowish brown anal plate. Up to 22 mm.

Food. Balsam fir, red spruce, white spruce, and less commonly other conifers.

Life Cycle. Typically one generation (some populations with 2-year life cycle). Recently hatched, tiny caterpillar overwinters in silken shelter under bark or in another protected area. Mature caterpillar present from May to July.

Comments. This caterpillar is the most destructive insect in many northern coniferous forests. In spring, the young caterpillar mines old needles, buds, and male flowers. The final two instars eat expanding buds or new foliage as they make webs that often bind the developing shoots together. After a caterpillar consumes all of the new needles, it will eat mature foliage. Rose and Lindquist (1994) and Johnson and Lyon (1991) have pictured the foliar damage. The spruce budworm and the pitch pine budworm, Choristoneura pinus maritima, are variable in color and sometimes cannot be identified to species without knowledge of the food plant.

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