Juniper scale
Carulaspis juniperi
26 host plants
Last updated
This profile contains verified pest data from extension databases. Regional field notes and expert review are in progress.
Juniper scale insects settle on juniper foliage, creating dense clusters of tiny, flat, gray or brownish circular bumps that coat needles and twigs. The scale covers are immobile and shell-like; you identify them by their numerous identical bumps giving infested areas a crusted appearance. Heavy infestations cause needle browning and branch dieback starting from the interior of the plant. Damage becomes apparent by midsummer.
Apply dormant oil in late winter or early spring before scale eggs hatch to smother overwintering stages. For active-season populations, horticultural oil targets the crawler stage in early to mid-spring. Prune out severely infested branches. For landscape junipers showing significant damage, a second oil application in early summer targets new generations. Maintain tree health.
Quick Reference
Juniper scale Egg hatch/crawler typically begins around 2563 GDD₃₂. As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂, approximately 970 units before the expected threshold.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 23, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,593 | Pre-season | Egg hatch/crawler | 970 |
| Seattle / UW | 1,554 | Pre-season | Egg hatch/crawler | 1,009 |
| Kent / Auburn | 1,537 | Pre-season | Egg hatch/crawler | 1,026 |
| Olympia / Tumwater | 1,505 | Pre-season | Egg hatch/crawler | 1,059 |
| Bellingham / Whatcom | 1,483 | Pre-season | Egg hatch/crawler | 1,080 |
| Tacoma / Puyallup | 1,472 | Pre-season | Egg hatch/crawler | 1,091 |
| Sequim / Rain Shadow | 1,434 | Pre-season | Egg hatch/crawler | 1,129 |
Source: Herms (OSU) phenological tables: 697 GDD₅₀ egg hatch, Dow Gardens MI 1985-1989 (Table 3); 571 GDD₅₀ Secrest Arboretum OH 1997-2001 (Table 4). Profile value 694 near-exact match with MI data. UMD IPMnet catalog corroborates. Updated 2026-04-03. About GDD₃₂ →
Cultural Controls
- Ladybird beetles and parasitic wasps help control scale infestations.
- Minor infestations may be wiped off by hand, when practical.
- Prune and destroy heavily infested branches to help control localized infestations.
- Provide proper culture.
- Healthy plants are more able to tolerate damage.