Obscure Scale – Control

Q: I recently got a note from a tree company that had been out inspecting my neighbor’s trees. It stated that they had discovered a insect pest known as “obscure scale” ravaging my neighbor’s pin oak trees.

A: I can’t judge whether the price is excessive – it all depends on how much you value the tree and how badly it is affected.

Obscure scale is a major pest of pin oak and several other trees. Like most scale pests, the female attaches herself to the bark of twigs and sucks sap from the tree. The result is gradual weakening and die-back. Obscure scale is so named because the waxy coating secreted by the female is almost identical to the color of tree bark.

An application of horticultural oil is the proper initial treatment for scale. The oil suffocates them quite effectively. An insecticide application when the immature crawlers emerge in spring prevents further infestation.

Virginia Tech has a nice factsheet (www.ext.vt.edu/departments/entomology/factsheets/obsscal.html) you can use to identify your pest and its life cycle. If you are comfortable climbing up in the tree to spray all branches and twigs, you could do the job yourself.