The valley oak, Quercus lobata, is attacked more frequently and severely than other species.
Damage can be severe in oaks along the Central Coast as well in the Central Valley.
A severe scale infestation delays leafing out of deciduous oaks for as long as 3 weeks in spring. Heavy attacks of pit scales year after year may kill young trees. The pitting effect caused by scales is most noticeable on the bark of younger twigs. If there are large numbers of scales, the pits coalesce, making the twig surface appear roughened and dimpled. The adult scale is a brown or dull green, flattened, circular, immobile insect about the size of the head of a pin.