Kuwana oak scale—Kuwania quercus
This sucking insect (Kuwaniidae) feeds on the bark of blue oak, Quercus douglasii.
Identification
Obvious roughening and exfoliation (flaking off) of bark are the apparent symptoms of infestation. Pieces of bark that have flaked off may cover the ground near the trunk. Gray or whitish wax that surrounds the preadult females can be seen under loose bark in the spring.
Adults and older nymphs are red, roundish, about 1/10 inch in diameter, and covered with gray or white wax. The scales occur mostly hidden under bark plates and in crevices on blue oak limbs and trunks.
Kuwana oak scale closely resembles the oak xylococcus scale, Xylococculus quercus, and Ehrhorn's oak scale, Mycetococcus ehrhorni. Both scales occur on the bark of various species of oaks, but neither causes obvious bark roughening or exfoliation.
Life cycle
The life cycle of this insect in California is mostly unknown. Preadult females are present in late winter. Mature females produce crawlers beginning in spring.
Damage
Scale feeding on blue oak causes extensive roughening and flaking off of the bark, exposing tissue underneath that is discolored and blackish. Other than the obvious bark roughening and flaking, whether the scale has long-term impacts on tree health is unknown.
Solutions
Nothing is known about managing this species of scale or whether management efforts are warranted to protect the health of blue oaks. Conserving natural enemies and applying horticultural oil or certain other insecticides are primary tactics for managing most scales.
For additional information, consult the Pest Notes: Scales, A Field Guide to Insects and Diseases of California Oaks, and The Scale Insects of California Part 2: The Minor Families.
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