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How to identify it
- Look on the undersides of the needles. The scales often sit in two long rows, one up each side of the needle.[1]
- UMass describes them as looking like a fried egg: the feeding nymphs and adult females are yellow, and each one makes a dense, oval, white wax cover around itself.[1]
- Old shed skins pile up under the cover as the nymphs grow, which adds to the fried-egg look.[1]
- Adult males have wings but live a very short time, so they are seldom seen.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Elongate hemlock scale | Elongate hemlock scale (Fiorinia externa) causes very similar needle yellowing and is far more widespread. The two armored scales damage Christmas tree plantings in southern New England together, so the needle symptoms alone won't tell you which one you have.[1][2] |
Where it lives
Introduced to North America from Asia, it is a serious pest from southern New England to the Southeast. In Massachusetts it is still uncommon and found only in the southeastern part of the state.[1]
Biology and life cycle
It feeds on many conifers but is most common on true firs (Abies) and hemlocks (Tsuga).[1]
It spends the winter as immature nymphs under their wax covers and starts feeding again in early spring. Males go through a pupal stage and fly off as winged adults to find females, then die after mating.[1]
In late May to early June each female lays about 40 eggs under her cover. The crawlers that hatch can spread to other branches or nearby trees, but they are fragile and must settle within a day, so many feed right beneath the dead mother.[1]
A second generation of crawlers appears in late August. Not all nymphs mature at the same pace, so the generations overlap, which makes treatments hard to time.[1]
Damage and signs
Health risk
UMass and the research literature treat it only as a pest of conifers; neither mentions bites, stings or any risk to people or pets.[1][2]
Control
Prevention
Check nursery stock for cryptomeria scale before planting.[1]
Sanitation
Remove and discard heavily infested trees, or prune out badly infested branches if the scale is still confined to the lower part of the tree. Clean pruning tools and mowers after working in infested areas so you don't carry crawlers to clean trees.[1]
Traps and physical control
Start scouting in late winter to early spring by turning over needles on the inner parts of lower branches and watching for trees with yellow-mottled needles. Yellow sticky cards hung on infested branches catch the winged males; egg hatch follows their flight by two to three weeks, at about 600 to 800 growing degree days, and the second crawler generation comes after about 1,750 to 2,130 growing degree days.[1]
Biological control
The twice-stabbed lady beetle (Chilocorus stigma) eats armored scales, this one included, and helps hold numbers down, which is why UMass advises against broad-spectrum insecticides. Research in Christmas tree plantings also names the predator Cybocephalus nipponicus and the parasitoid Encarsia citrina as natural enemies of these scales.[1][2]
Pesticides
If overwintered scales are present in spring, dormant oil can be applied before bud break, with thorough coverage of the lower needles. Dinotefuran is labeled for cryptomeria scale: applied as a spray or drench to the lower trunk, it is absorbed through the bark and carried to the needles, and in field trials on Christmas tree farms it worked well without significantly harming the scales' predators. Banding it on the soil gave poor control, the bark spray worked less well on taller trees, and spraying from late April (before bud break) to mid-June was effective, with earlier sprays letting fewer crawlers discolor the new growth.[1][2]
Common questions
- Why are the lower branches of my fir or hemlock turning yellow?
- Cryptomeria scale is one possible cause: it yellows and mottles needles on the lower and inner branches and makes them drop early. Turn the needles over and look for rows of small oval white covers with a yellow center. Elongate hemlock scale causes similar symptoms.[1]
- Does cryptomeria scale only attack Japanese cedar (Cryptomeria)?
- No. Despite the name, UMass says it occurs on many conifers and is most common on true firs and hemlocks.[1]
- When is the best time to treat cryptomeria scale?
- Dormant oil goes on before bud break if overwintered scales are present. For the crawlers, use sticky cards to spot the males' flight and expect egg hatch two to three weeks later; in field trials, basal bark sprays of dinotefuran applied from late April to mid-June were effective.[1][2]
Sources
- UMass Extension Landscape, Nursery and Urban Forestry Program, “Cryptomeria Scale (S. Scheufele and N. Brazee, fact sheet, revised 2014).” www.umass.edu/agriculture-food-environment/landscape/fact-sheets/cryptomeria-scale (accessed 2026-11-09)
- Entomological Society of America (Journal of Economic Entomology), “Cowles RS. Optimizing a basal bark spray of dinotefuran to manage armored scales (Hemiptera: Diaspididae) in Christmas tree plantations. Journal of Economic Entomology 103(5):1735-1743 (2010) (abstract).” doi.org/10.1603/ec10077 (accessed 2026-11-09)
- iNaturalist, “Aspidiotus cryptomeriae taxon page (order and family).” www.inaturalist.org/taxa/1188356 (accessed 2026-11-09)