|You can rid your defenseless trees and shrubs of inconspicuous killers by using a prophylactic spray. The spray which should be used is referred to and sold under many brand names as dormant oil or scale emulsion.
These are highly refined oils (not motor oils!) which spread uniformly on the bark of trees and shrubs to which they are applied and coat non-mobile, dormant insects on the tree smothering them to death.
Heavier oils may have to be applied with a tank (pump-up) sprayer which can apply the fully diluted product rather than with a hose-end sprayer which may become clogged. Applicators should frequently shake sprayers to agitate the water and chemicals mixed since plant damage can occur if a concentrated oil spray, caused by solution separation, is applied. Mix dormant oil at the recommended rate on the product label.
It is best to spray before buds begin to swell. If buds of trees and shrubs have begun to swell slightly, go ahead and spray. Although some of the buds may be damaged, the benefits of spraying dormant oil far outweigh the possible repercussions.