Insecticide application is the only tool currently available for managing these pests. Because heavy infestations over several years can kill young trees and weaken older ones, consider management actions as soon as problems are detected. These applications must be made by a professional pest control applicator. Residents wishing to treat deciduous trees in their landscapes can apply narrow-range insecticidal oil to trees in spring just before the buds open. Be sure to cover all bark and branch tips thoroughly.
Thorough coverage can be difficult with very large trees unless high-pressure equipment is used.
However, infestations on small to medium-sized trees can be adequately managed with one annual application over several consecutive years. Once leaves are on the tree, it is too difficult to get the degree of coverage needed for oil treatments to be effective. Mixtures of oil and organophosphate insecticides applied in spring to kill hatching crawlers are not recommended because of the environmental hazards associated with applying these insecticides to large trees in residential areas, the difficulty of getting adequate coverage with available application equipment, and the availability of safer, more effective alternatives. Pit Scales on Oak. The Regents of the University of California.