Incense cedar scale, or Monterey cypress scale—Xylococculus macrocarpae
This sucking insect (Xylococcidae) causes foliage discoloring and dieback on incense cedar, Monterey cypress, and various Cupressus and Juniperus spp., especially on young plants growing at shaded locations. It usually is common only in stands of native conifers, not in urban areas.
Identification
This scale is easily overlooked and often will be found only by peeling back layers of loose bark.
Nymphs and females are oblong, dark reddish to brown, and wingless. Mature females are about 1/4 inch long. The tiny, winged adult males are easily overlooked; they are 1/8 inch long and have legs and long, thin antennae.
The incense cedar scale preadult female (cyst, or resting stage) is 1/8 inch long and closely resembles the cypress bark mealybug. Both species can occur on the same hosts.
Incense cedar scale and cypress bark mealybug do not resemble the minute cypress scale. All three of these species are sometimes called cypress scale, but they are in separate insect families and have different biology.
Adult females lay eggs on the foliage in spring. Eggs hatch into mobile first instars (crawlers) that settle to feed on branch and trunk bark and molt to legless stages in the summer. In addition to the egg, there are four female stages and five male stages.
Females overwinter as legless second and third instars (stages), and males as legless second instars and legged prepupae on bark. In early spring, females molt into legged adults and moved to foliage; the males occur on bark and pupate into winged adults. The scale has one generation per year.
Damage
Scale infestation is indicated by the blackish appearance of the trunk and larger branches caused by sooty mold. Bark may also exhibit mealy, white wax produced by the scales.
Solutions
Conserving natural enemies and applying horticultural oil or certain other insecticides are primary tactics for managing scales. For additional information, consult the Pest Notes: Scales.
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