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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.

Do not spray trees which are in full bloom however. Applying a dormant oil spray this late will also serve to cover pruning cuts and can serve as a second attack on stubborn pests which were not killed by an earlier oil application. The closer the application is made to budbreak, the greater the kill.

Spraying of dormant oil should occur on a clear day when the temperatures are expected to remain over 50° F for at least twenty-four hours. The ideal temperature for application is between 40 and 70° F in order to get the oil to spread out over the tree and cover all crooks and crevices. Try to avoid applying dormant oil when severe freezing trends are expected in the 3-4 days following application.

The use of a dormant oil mixture will annihilate annual flowers such as pansies or snapdragons growing under or near plants to be treated. Completely cover such tender vegetation before spraying dormant oil.