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How to identify it
- Mature females are highly convex, almost spherical, 3 to 5 mm (about 1/6 inch) wide, and for most of the year dark chestnut brown and shiny with numerous darker sunken spots, so a row of them looks like beads on the stem.[1][3]
- For a short period in late spring, just before egg laying, the females turn yellowish or orange with seven or eight black crossbands or blotches and a diffuse orange or red stripe down the middle.[1][3]
- Unlike the soft scales it resembles, Kuno scale has a broad internal lip or shelf-like margin where the body attaches to the twig; pry a female off and look at the underside to see it.[1][3]
- Nymphs are flat and yellow or brown with a fringe of wax, found in summer mostly along the veins on the undersides of leaves. Elongate, translucent male cocoons about 1/12 inch long can be common on twigs.[1][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Calico scale | A related Eulecanium soft scale that UC lists on liquidambar, box elder, maple, stone fruit and walnut; Kuno scale is the one with shiny chestnut brown, bead-like females and a broad internal attachment lip on the underside.[2][1][3] |
| European fruit lecanium (brown apricot scale) | Another brown soft scale of stone fruit, walnut and many trees; Kuno scale is told by its almost spherical shape, the spring black banding and the internal lip on the underside.[2][1] |
| Frosted scale | Another soft scale UC lists on walnut, ash, birch, elm, locust, pistachio, rose and sycamore; Kuno scale is nearly spherical and shiny brown with the black spring banding.[2][3] |
Where it lives
Recorded in the United States from California, where it is most abundant on garden and landscape plums.[3][1]
Biology and life cycle
Hosts are stone fruits, especially plum, and other woody Rosaceae such as cotoneaster, pyracantha and rose, plus walnut; only plum and other stone fruit are sometimes damaged. It is not a pest on commercial fruit and nut crops in California.[1][2]
One generation a year. Nymphs overwinter on twigs and mature into adults from March through early May. Eggs laid beneath the female hatch in spring into crawlers that move out to the leaves and settle along the veins on the undersides for the summer; the nymphs return to the twigs before the leaves drop in fall.[1][3]
Kuno scale sucks phloem sap from leaves and twigs, can become abundant quickly, and produces copious honeydew. ScaleNet calls it a minor pest of ornamentals in California but a potential pest in the state.[1][3]
Damage and signs
- Heavy infestations make the host look water stressed, and prolonged high populations cause premature leaf drop and twig dieback. The copious honeydew grows blackish sooty mold and attracts ants.[1]
Health risk
Neither source mentions any effect on people or pets; the nuisance is sticky honeydew, sooty mold and the ants it attracts.[1][3]
Control
Prevention
Check plum twigs in winter and spring for the shiny brown beads and watch for honeydew and ants, which signal a growing population. UC advises oil only where the scale has been abundant.[1]
Biological control
Natural enemies attack soft scales, and ants protect the scales from them; control the ants so parasites and predators can work.[1]
Pesticides
If the scale has been abundant, spray horticultural oil on branch terminals and twigs during the delayed dormant period, as buds begin to swell, or thoroughly drench the undersides of the leaves in early summer when the nymphs are there. Do not spray fully dormant plum or walnut trees with oil, do not apply oil when temperatures will exceed 90 F, and do not treat trees that have been short of soil moisture.[1]
When to call a professional
For a large or badly declining plum, an arborist or certified applicator can time a delayed-dormant oil application and check that the tree is not drought stressed before treating.[1]
Common questions
- What are the shiny brown balls stuck along my plum twigs?
- Almost certainly Kuno scale: adult females are nearly spherical, dark shiny brown, about 1/6 inch across and look like beads on the stem. Lift one off; a broad internal lip on the underside confirms it.[1][3]
- When do the crawlers hatch?
- In spring. Adults mature from March into early May, lay eggs beneath their bodies, and the crawlers hatch and move to the leaf undersides for the summer before returning to twigs in fall. There is one generation a year.[1][3]
- Why is my tree covered in sooty mold and ants?
- Kuno scale produces copious honeydew, which grows blackish sooty mold and feeds ants. Controlling the ants lets the scale's natural enemies recover, and an oil spray at delayed dormant or on the leaves in early summer brings heavy populations down.[1]
Sources
- University of California Statewide IPM Program, “Kuno Scale (Home and Landscape pest page).” ipm.ucanr.edu/home-and-landscape/kuno-scale/ (accessed 2026-11-10)
- University of California Statewide IPM Program, “Pest Notes: Scales, UC ANR Publication 7408.” ipm.ucanr.edu/home-and-landscape/scales/ (accessed 2026-11-10)
- ScaleNet (scale insect database begun at the USDA ARS Systematic Entomology Laboratory), “ScaleNet catalogue: Eulecanium kunoense (Kuwana, 1907).” scalenet.info/catalogue/Eulecanium%20kunoense/ (accessed 2026-11-10)
- iNaturalist, “Eulecanium kunoense taxon page (order and family).” www.inaturalist.org/taxa/81854 (accessed 2026-11-10)