What Is It?
This beetle (Agrilus anxius), native to North America, is 7-11 mm in length and dark green-bronze in color.
What's the Problem?
This insect is often considered a secondary pest that attacks birch trees already stressed by things like drought. If populations build high enough on stressed trees, however, the beetle may move on to attack healthy trees.
Attacks result in progressive dieback of the crown and death of the tree within a few years. Injury is caused by the larvae feeding under the bark.