Cooley spruce gall adelgid
Adelges cooleyi
20 host plants
Last updated
Cooley spruce gall adelgids create distinctive cone-shaped galls on spruce new growth, becoming miniature pinecones by late summer; galls range from light green to deep purple and measure one and a half to three inches long. You will see these galls at branch tips and along new shoots from spring into early fall on various spruce species. Though rarely harmful to tree health, heavy infestations can disfigure branches by destroying buds and distorting tree form.
No cultural control needed; most trees tolerate galls. Prune heavily galled branches on ornamental specimens if appearance is critical. Natural predators usually keep populations light. Apply horticultural oil during dormancy only if gall disfigurement significantly affects landscape value.
Quick Reference
Cooley spruce gall adelgid Egg hatch typically begins around 1424 GDD₃₂. As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂, approximately 243 units before the expected threshold.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | Pre-season | Egg hatch | 243 |
| Seattle / UW | 1,171 | Pre-season | Egg hatch | 253 |
| Kent / Auburn | 1,111 | Pre-season | Egg hatch | 313 |
| Olympia / Tumwater | 1,106 | Pre-season | Egg hatch | 318 |
| Bellingham / Whatcom | 1,101 | Pre-season | Egg hatch | 323 |
| Tacoma / Puyallup | 1,075 | Pre-season | Egg hatch | 349 |
| Sequim / Rain Shadow | 1,070 | Pre-season | Egg hatch | 354 |
Source: Herms (OSU) phenological tables: 308 GDD₅₀ egg hatch, Secrest Arboretum OH 1997-2001 (Table 4); 283 GDD₅₀ Dow Gardens MI 1985-1989 (Table 3). UMD IPMnet Pest Predictive Calendar corroborates (Gill & Klick). Updated 2026-04-03. About GDD₃₂ →
Cultural Controls
- Planting spruce and Douglas fir trees as far apart as possible may help reduce (but not prevent) adelgid infestations.
- Galls may be pruned out to improve the short-term appearance of infested trees.
- Long-term pruning may ruin tree's shape.
- Most spruce species in the Pacific Northwest are susceptible.