Bronze birch borer

Look for D-shaped emergence holes in birch bark with nearby sawdust trails; branch dieback progresses from upper canopy downward on affected trees. Beneath bark you will find white flattened larvae about 1 inch long creating winding galleries along cambium. Stressed, drought-weakened, or older birch trees are most vulnerable.

Maintain tree vigor through consistent deep watering during dry summers; this is single most important control. Prune out dead and dying branches during winter dormancy to reduce beetle reproduction. Preventive trunk sprays of permethrin in late May to early June protect specimen trees from newly emerged adults. Once larvae establish galleries, no insecticide reaches them.