Symptoms: Their are two major signs of infestation of scale insects on landscape plants. The scale itself appears as crusty, waxy bumps on the stems or twigs of the infested plant. Also, like most sucking insects, the droppings of scales is a sweet substance called honeydew. This accumulates on lower leaves and branches and supports a growth of sooty mold. Badly infested plants may have yellow leaves and may have twigs or small branches that die.

Diagnosis: Many species of scale insects commonly infest landscape trees and shrubs. Some such as the magnolia scale, euonymus scale or pine needle scale are specific to their host plant. They are all sucking insects that do their damage by pulling sap from the tender stems.


First, as always, you must properly identify the species of the scale on your plants. Consult your local Extension Service office or other plant professional. They should be able to tell you the life cycle of that species and when the young (crawlers) are active.

Three approaches may be taken to reduce the number of scale on the plant:

1. A dormant (horticultural) oil spray may be used to smother both the adults and the crawlers. Plants may be sprayed with a highly refined petroleum product such as Volck oil or Sunspray Ultra Fine oil at the dormant rate. The temperature must be high enough (usually 40 degrees for several days) so that the oil will spread evenly over the branches and thus smother the scale insects.

 2. When the crawlers emerge, they may be controlled by an oil spray applied at the growing season rate (more dilute) listed on the product. Or, they may also be treated with other insecticides labeled for your species of scale. 

3. Some systemic insecticides may be labeled for use on scale. Check the label of the product to be sure that the species of scale and your species of plant(s) are listed.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


Types of Insects

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