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How to identify it
- The female cover is circular to oval, flat, 1.3 to 2 mm long and nearly as wide, dark gray to almost black in the center with a paler margin, sometimes tinged bluish, brownish or purple; the shed skins sit at the center. Male covers are smaller, elongate oval and blackish, with the shed skin near one end.[4][1]
- Sources describe the cover's color a little differently: dark gray, often nearly black, with a paler rim (ScaleNet); dark gray or nearly black (USDA Forest Service); dark brown-gray (UMass); dark brown (Cornell Cooperative Extension).[4][3][1][2]
- Beneath the cover the female's body is yellow-green and the eggs are pale yellow. Winged males occur.[1]
- Scales sit on the underside of the needle; a small yellow spot on the upper surface above each one is the first sign of feeding. Cornell notes that mature scales are always found on the undersides.[1][2]
- Do not confuse it with the elongate hemlock scale (Fiorinia externa) or with the introduced shortneedle evergreen scale, a smaller, strongly convex, dark brown scale with a nippled center that shares the same hosts.[1][5][2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Shortneedle evergreen scale | An introduced armored scale from Japan on hemlock, spruce, fir and yew with a smaller (1 to 1.3 mm), strongly convex, dark brown cover with a nipple at the center. The hemlock scale is native, flat, dark gray with paler margins and about 2 mm across.[5][4] |
| Elongate hemlock scale | Fiorinia externa, also an armored scale of hemlock needles; UMass warns against confusing the two. The hemlock scale's cover is round to oval, dark gray with a paler margin.[1][4] |
Where it lives
Known only from the United States. ScaleNet has records from Connecticut, New York, Pennsylvania, Ohio, Indiana, Maryland, Virginia, West Virginia, Tennessee, Georgia and Alabama in the East and Idaho, Montana, Oregon and Washington in the West; the USDA Forest Service's eastern guide describes it as a scale of the eastern United States.[4][3]
Biology and life cycle
Hemlock is the preferred host; fir, spruce, Douglas-fir and pine are also attacked. ScaleNet records it from eastern and western hemlock, grand fir, white and Colorado spruce and Douglas-fir, and Cornell Cooperative Extension says it can be particularly damaging to blue spruce.[1][4][3][2]
Two generations a year are reported in Maryland. First-generation eggs may hatch in June, with scales maturing by late July and laying second-generation eggs in August and September; second-generation crawlers settle on the needles and overwinter as second instars.[1]
Growing degree day timing (base 50 F from March 1) is 35 to 121 GDD for the dormant stage and 1388 to 2154 GDD for the summer stage.[1][2]
Wasp parasites keep it in check most of the time. Cornell names Aspidiotiphagus citrinus as an important one, and parasites emerge four times a year, in April, June, July and August (reported from Maryland in the UMass guide).[2][1]
Damage and signs
Health risk
None of the sources mentions any effect on people or pets; they treat it only as a pest of conifer needles.[1][4][2][3]
Control
Prevention
Inspect the undersides of hemlock and fir needles with a hand lens when yellow flecks appear on top, and separate this native scale from the elongate hemlock scale and the shortneedle evergreen scale before choosing a plan.[1]
Traps and physical control
Remove and destroy infested branches when that is practical.[1]
Biological control
Parasitic wasps usually keep the hemlock scale in check. Don't use scale insecticides while the parasites are emerging (April, June, July and August), and avoid needless broad-spectrum sprays.[2][1]
Pesticides
Cornell advises pesticides only where hemlocks are being badly damaged: a dormant horticultural oil at 35 to 121 GDD, or, if that was missed, oil at the summer rate at 1388 to 2154 GDD, when abelia or false spirea (Sorbaria sorbifolia) bloom.[2]
Massachusetts lists horticultural oil, insecticidal soap, neem oil, azadirachtin, buprofezin, pyriproxyfen (for eggs) and systemic active ingredients such as acetamiprid, dinotefuran and imidacloprid for the hemlock scale; make applications after bloom to protect pollinators, and note that neonicotinoids are state-restricted for tree and shrub pests in Massachusetts. First-generation crawlers hatch around June and second-generation crawlers in late summer in Maryland.[1]
Common questions
- Yellow flecks on top of my hemlock needles, round dark dots underneath. What is it?
- That pattern fits the hemlock scale: a native armored scale about 2 mm across, dark gray to dark brown, feeding on the needle underside and leaving a yellow spot above. Check it is not the smaller, convex, nippled shortneedle evergreen scale or the elongate hemlock scale.[1][4][2][5]
- How many scales does it take to hurt the tree?
- Four to six per needle can yellow the needle and make it drop, and heavy infestations have caused branch dieback and defoliation.[1][2]
- When are crawlers active?
- In Maryland, first-generation eggs hatch around June and the second generation's in August and September; those late crawlers settle and overwinter on the needles as second instars.[1]
Sources
- UMass Extension Landscape, Nursery and Urban Forestry Program, “Hemiberlesia (formerly Abgrallaspis) ithacae, hemlock scale, Professional Insect & Mite Management Guide for Woody Plants.” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/hemiberlesia-formerly-abgrallaspis-ithacae (accessed 2026-11-11)
- Cornell Cooperative Extension, Nassau County, “Scale Insects (Home Grounds Fact Sheet E-1-31).” ccenassau.org/resources/scale-insects (accessed 2026-11-11)
- USDA Forest Service, “Eastern Forest Insects, Miscellaneous Publication 1175 (W. L. Baker, 1972; scanned copy).” archive.org/details/easternforestins1175bake (accessed 2026-11-11)
- ScaleNet (scale insect database begun at the USDA ARS Systematic Entomology Laboratory), “ScaleNet catalogue: Hemiberlesia ithacae (Ferris, 1938).” scalenet.info/catalogue/Hemiberlesia%20ithacae/ (accessed 2026-11-11)
- UMass Extension Landscape, Nursery and Urban Forestry Program, “Dynaspidiotus (formerly Nuculaspis) tsugae, shortneedle evergreen scale, Professional Insect & Mite Management Guide for Woody Plants.” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/dynaspidiotus-tsugae (accessed 2026-11-11)
- iNaturalist, “Hemiberlesia ithacae taxon page (order and family).” www.inaturalist.org/taxa/1511298 (accessed 2026-11-10)