More on armored scales

Howard Russell, MSU Diagnostic Services -

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.    

Pine needle scale belongs to the family Diaspididae, which are commonly known as armored scales. Other common armored scales are oystershell scale and euonymus scale. The other family of commonly encountered scales in home landscapes is the soft scales in the family Coccidae. Examples of common soft scales include pine tortoise scale, magnolia scale and European fruit leucanium scale. Of these two types of scales, armored scales are much more difficult to control because dormant oil treatments and neonicotinoid insecticides are not effective in controlling armored scales. Control of armored scales requires well-timed insecticide applications when the crawlers emerge from the beneath the waxy scale covering.

It is important then to be able to distinguish an armored scale from a soft scale when considering the most effective control measures. Listed in the table below are several characteristics that can be used to separate armored and soft scales.

Characteristics of armored scales (Diaspididae) Characteristics of soft scales (Coccidae)
Previous exuviae (cast skins) remain attached to scale covering. Previous exuviae (cast skins) do not remain attached to scale covering.
Body of the scale easily separated from the scale covering. Body of the scale does not separate from the scale covering.
Do not produce honeydew, therefore sooty mold not present on leaves and twigs. Often produce copious amounts of honeydew, which is readily colonized by sooty mold.
Overwinters as mature females or eggs. Overwinters as nymphs.
Dormant oil treatments are ineffective control measures. Dormant oil treatments are generally effective control measures.
Neonicotinoid insecticides (e.g. imidacloprid) are ineffective control measures. Neonicotinoid insecticides (e.g. imidacloprid) can be effective control measures.
Control measures must be aimed at the crawler stage, therefore application timing is critical. Control measures are not limited to controlling crawler stage.

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