Origin:
Uncertain, but possibly native to North America.
Biology:
The scale is unusual in that mature forms may still be mobile, and it is these that move from leaves to bark to overwinter. In late winter the eggs are produced and the mobile crawlers move to leaf buds as they begin to open in early spring, settling on undersides of leaves to feed. After feeding the mature scales once again move to the bark to produce eggs for the next generation, and there usually are several generations each year. Only varieties of sycamore trees are attacked by this scale. They may also feed on soft bark, causing a roughened texture to it. Feeding on the leaves causes small yellow spots which then turn brown as the tissue dies. Young leaves may grow in a distorted manner and prematurely drop from the tree.
Identification:
The scale is extremely small, only 1/16 inch long, and the best evidence is the yellow spots developing on the undersides of sycamore leaves. Close examination reveals the scale within the spot. The scales change from orange to brown in color as they develop, and mature females will have small white tufts of wax protruding from the edges of the wax shell.
Characteristicts Important to Control:
Chemical sprays when the tree is fully leafed out may be ineffective due to the positioning of the scales on the undersides of the leaves. Treatment during the winter with dormant oils thoroughly applied to branches and twigs will kill overwintering scales and eggs. A treatment timed for bud break can affect the most scales at their crawler stage when they are exposed, and before the leaves fully expand to protect them.
