Lace Bugs on Oak

The landscaper did not see any insects on the undersides of the leaves but did see something that looked like black beard stubble on a few of the leaves. The black beard-like stubble on the oak leaves' undersides were eggs laid by the oak lace bug. Oak lace bugs have piercing-sucking mouthparts and will cause a bronzing or stippling of the oak foliage. There are typically 3–4 generations a year in Pennsylvania, and overwintering adult females will begin laying eggs in the spring after the oak leaves have fully expanded and will continue egg-laying until late summer or early fall.

Oak leaf displaying stippling or bronzing on the upper leaf surface after being attacked by oak lace bugs. Photo: Thomas Ford, Penn State

The injury caused by the oak lace bug is largely aesthetic and will cause minimal injury to the tree. High-value specimens may be treated with a systemic insecticide after bloom using a soil drench containing imidacloprid. In most cases, it is best to ignore this nuisance oak pest since the injury typically does not warrant control.