Are You Acquainted With The Bronze Birch Borer Beetle?

We know this is a creepy question but if you have a birch tree in arid northern Nevada or drought-ridden California, you may be more intimately connected to this pest than you realize. According to the Horticulturist department at the University of Nevada Cooperative Extension (UNCE), the Bronze Birch Borer has “killed several thousand mature birch trees in urban areas along the Sierra Front”. Trees may be infested for several years before there are visible symptoms. Because the infestation often goes unnoticed, the beetles have time to create a lot of harm and it becomes extremely difficult to save the tree.

Keeping an eye on the general health of your trees is always important but even more so when it comes to preventing these bugs. Although Borer beetles will attack healthy trees, they prefer trees stressed by drought, soil compaction, and or infected by other insects. Birch trees thrive in cool moist soil and have a shallow root system that does not do well in dry hot conditions. A healthy tree can produce callus tissue where the birch borer larvae feed. If enough callus can be produced quickly, the larva die, if not, the tree becomes susceptible to repeated attacks. After several attacks, the larvae disrupt the tree’s nutrient transport and the roots die. A tree with a damaged root system can’t supply leaves with enough water and branches die. This infestation cycle leads to the tree’s complete demise.

Preventative care is your first line of defense in saving your birch trees. Plant birch trees where the soil will be cool and moist, keeping in mind that they do require some full to partial sun on their leaves. At least once every few weeks you need to do a slow deep watering to maintain soils moisture levels. Mulching is important and beneficial because it reduces competition with turf and moderates soil temperatures and moisture levels. Watch the fertilization though, fertilizing is beneficial, but too much nitrogen increases succulent growth and this attracts the insidious pest! Fertilization is not recommended if your trees are showing signs or symptoms of a Bronze Birch Borer infestation.


The urgency for a treatment plan is high if you do notice symptoms of this beetle. Look for:

  • Dead tips of branches and yellowing sparse foliage.
  • Dying branches and thinning leaves at the top of the tree.
  • Top-down dieback in the upper third of the tree.
  • Distinctly D-shaped exit holes often accompanied by rust colored sap.
  • Swelling where larvae have tunneled under the bark and raised welts or ridges in a zigzag pattern.

Drought like conditions have encouraged the spread of the Bronze Birch Borer, if you notice any of the signs, move quickly to save your tree… once a tree has 30 percent dieback it is unlikely to recover and treatment is expensive. Insecticides can be applied to the tree bark to kill larvae from emerging eggs. This treatment will not kill larvae already under the bark, but it will help prevent new attacks.

If your birch trees are showing any signs of stress give us a call at Joe Benigno’s Tree Service. Unfortunately for the Bronze Birch Borer Beetle, we are acquainted with the signs and symptoms of its infestation patterns. If we get to work quickly, we may be able to save your trees and rid you of this pest!

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