Origin:
A probable native insect in North America.
Biology:
This scale is primarily a pest of eastern North America in hardwoods of oak, pecan, elm, hickory, and hackberry, and chestnut found in landscape settings. The scales may be found on softer bark of twigs, trunks of young trees, and even exposed roots. Heavy infestations can weaken trees due to loss of sap and extensive covering of the bark that interferes with movement of oxygen into the tree. Trees are rarely killed but dieback of outer growth may occur. Eggs are deposited and hatch throughout the warm months, and crawlers move about on the tree until they finally settle onto one place and become sessile, now covering themselves with a wax shell. Males and females mate in early summer and the female produces a large batch of eggs under her wax shell. Just prior to crawler emergence the female creates an opening in the wax for the crawlers to exit through.
Identification:
The wax scale is diagnostic, and typical of armored scales it is flattened and small, gray to brownish and often very similar in appearance to the bark of the tree, making it nearly invisible. The scale is only 3 mm across, but repeated generations of crawlers may reside under old scales, building up the overall amount of wax covering the bark. The actual insect under the wax may be pink to yellow in color.
Characteristicts Important to Control:
Dormant or summer oils may be effective in killing the scales, as well as contact insecticides applied when the first instar crawlers are present. Determining the effectiveness of the control effort is difficult. The wax scales adhere tightly to the plant, even when the actual insect is no longer living, and very close examination beneath the scale may determine whether the insect itself is dead or alive.
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