Adelges (Gilletteella) cooleyi (Gillette) typically host-alternates between Picea spp. (engelmanni, pungens, sitchensis) and Pseudotsuga spp. (macrocarpa, menziesii).

The galls on shoot tips of Picea are characteristically elongate, with green, pink or red gall chambers and long needles protruding from them. Apterous exules on needles of Pseudotsuga are covered in white woolly wax.

Native to western North America, but now occurring throughout Europe and North America, and in Tasmania. Cumming (1962) described a monomorphic, non-galling, anholocyclic form on Picea glauca in Canada ...