Minute cypress scale—Carulaspis minima
Minute cypress scale, an armored scale (Diaspididae), is also called cypress scale. It can occur on almost any conifer and is common on arborvitae, cypress, and juniper. Minute cypress scale usually is a serious pest in landscapes only on Italian cypress, Cupressus sempervirens, and in nurseries on various conifer species.
The alternative name cypress scale is also applied to species including the cypress bark mealybug (cypress bark scale) and incense cedar scale (Monterey cypress scale). The foliage discoloration and twig dieback caused by minute cypress scale can resemble that caused by the larvae (caterpillars) of certain moths, including cypress tipminer, juniper twig girdler, and webworms such as cypress leaftier, cypress webber, and juniper webworm. These species can occur together.
To help diagnose the cause of damage, shake foliage to see if numerous tiny moths are dislodged. Look for caterpillars and silk produced by larvae of these moths. The caterpillars grow to 1/4 inch or longer and chew and feed on or inside of foliage.
Use a hand lens to inspect discolored foliage for the scales, which are 1/16 inch long or less and do not produce silken strands. The cover of mature females of minute cypress scale is circular, convex, and whitish with a brown to yellow center. The scale body under the cover is greenish and yellow. The cover of immature males is elongate, feltlike, and with longitudinal ridges; on the terminal of males' mostly whitish cover is the brown or yellow exuvia (cover of the earlier, nymphal stage).
Juniper scale. Carulaspis juniperi in the field cannot be distinguished from minute cypress scale. Both species can be present. The covers of both species are circular to elongate, tiny, and found on leaves and stems.
Minute cypress scale overwinters as females, which mature and produce crawlers (mobile, first instars) in late winter and spring. Nymphs feed through the summer, develop into adult females or males, and mate. Males die by the fall and only females are present during the winter. There are one to two generations per year in California.
The scale feeds by sucking plant juices from leaves (needles) and twigs. Severe infestations can cause foliage to turn yellow or brown and die. Although minute cypress scale is widespread in California, it generally is not a serious pest in landscapes. It can be a serious pest in nurseries.
Generally no control is warranted in landscapes where the scale's populations are commonly innocuous. Parasitic wasps, predatory lady beetles, and other natural enemies commonly feed on and kill the scale. If scale damage is intolerable or adversely affecting plant health, thoroughly spray infested foliage with horticultural oil when monitoring indicates that crawlers are active in the spring. Use a different, effective insecticide if the product label indicates the host plant is sensitive to oil damage.
See Carulaspis minima from the U.S. Department of Agriculture and others for more information.
Adapted from Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
Female and male minute cypress scales.
A female (center) and males of juniper scale appear the same as minute cypress scale.