Bronze birch borer, Agrilus anxions, is a native wood boring beetle that attacks birch trees that are stressed by drought, soil compaction or other insects. Birch trees prefer cool, moist locations which are not often found in residential or urban areas, therefore many urban birch trees are at risk of bronze birch borer attack.
The Beetle & the Birch Tree
Just like most wood boring beetles, it is the larval stage of bronze birch borer that causes damage. The larvae feed on the sapwood of the tree, disrupting the flow of water, nutrients, and sugar. Trees may be infested for several years before they begin showing visible symptoms. Preventative treatments are typically required to maintain these trees health, especially as they mature.
BRONZE BIRCH BORER SYMPTOMS
Yellowing of leaves, just below dead tips of branches.
Thinning leaves and branches at the top of the tree.
Top-down dieback, occurring in the upper third of the tree first, showing yellowing then death.
D-shaped exit holes. Bronze birch borer is a flat-headed borer, so when it emerges as an adult it chews a distinctly D-shaped hole.
Swelling where larvae have tunneled underneath the bark.