Abgrallaspis ithacae
Pest description and damage Scale insects are small (less than 0.125 inch in length) soft insects that live beneath waxy scales. These insects are often identified by the shape and size of their scales, the description of adult males and females, immature crawler stage, color of eggs, and host plant preferences. Hemlock scale insects feed on the needles of Eastern hemlock (Tsuga canadensis) and spruces (especially Colorado blue spruce). Adult scales are round to oval, dark gray or black, and about 0.1 inch in diameter. Immature scales (crawlers) are green to yellow. Scales typically are found as small bumps on the underside of needles. Scales feed on the needles by sucking out the cell contents. The initial symptom of infection is yellow spots on the upper surface of the needles. As few as four to six scale insects per needle will cause needle-drop. Colorado blue spruce loses large numbers of needles. Severe infestations may weaken trees sufficiently to cause death. The hemlock scale is most common on stressed trees.
For biology, life history, monitoring and management
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Management-chemical control
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