Scale Insects

Most people do not recognize scale as actual insects since they show little resemblance to the typical insect. They are well protected because they live under a waxy, almost impermeable shell. The female lays her eggs under this shell which offers them protection. When the eggs hatch, the "crawler" stage emerges. It is mobile and will crawl about on the host plant to select a feeding site. It is during the crawler stage that they are most easily controlled with insect controls. Except for the males of some species, adult scales will permanently attach themselves to a position selected during the crawler stage. Scale infestations frequently go undetected until the plant is completely covered. A needle like mouth part is inserted into the plant and sap is sucked out. Scale insects will also secrete a sticky substance called "honeydew" which can coat surfaces below the plant. A fungus called sooty mold can then survive on the honeydew.

Scale insects can be categorized as either armored or soft shelled. Armored shelled scales are small(1-2mm), permanently attached, hard flat, circular to elongated and crusty, whereas soft shelled scales are frequently larger (up to 6mm), soft bodied, sometimes mobile, hemispherical and dark.

Proper plant care, including pruning of heavily scale infested branches, is a primary management strategy. Insect controls are often needed. Horticultural oils applied in the spring will help to suffocate overwintering eggs. Properly timed applications of insect controls will also be beneficial in controlling the crawler stage. This is when the insect is in the crawler stage and has yet to develop its shell. Adult scale insects are difficult to control. At this time, systemic insect controls can be applied.

Information gathered from the Green Tips, Michigan State University and the University of New Hampshire. Feb 02 RN