Oak Pit Scale Oak Pit Scale Several species of pit scales attack many of the common deciduous and evergreen oaks that grow in California. 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.
Dead leaves and twigs on affected trees remain throughout the winter, giving the tree an unsightly appearance. 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. Pits are surrounded by a doughnut-shaped swelling with the scale in the center.