There are two broad categories of scales, soft and hard. Scale are sucking insects that stick their snout into plant tissue and remove the rich sap. Armored (hard) scale form thin bumps that are either round or oblong that form on tender shoots of plants. Once established on the plant the scale produces a kind of "dome" over itself to protect it from predators. This also protects them from being killed by common insecticide sprays for most of their life cycle.

The female scales produce eggs and the young hatch out beneath the covering dome. They leave the shelter and are then called "crawlers" as they move around the plant in search of a place to call home. During the 2 or 3 weeks that the crawlers take to begin to feed and build their own shell, they are vulnerable to common insecticides.

Unlike some other forms of scale, armored types do not produce droppings called honeydew. Therefore, there will NOT be sign of the black fungus called sooty mold on lower leaves of the plant.

The key signs will include discovering the actual scales on the soft tissue of the plant.

 
 

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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