Bronze Birch Borer

Scientific Name: Agrilus anxius

Bronze Birch Borer is a native beetle that attacks birch trees throughout North America. In urban landscapes it is primarily a pest of white-barked birch cultivars that are either planted in the wrong place (stressed environment) or that have no innate resistance to the beetles (Asian and European birches). This pest will kill untreated trees that become infested.

Attacks: All birch species

• European and Asian hybrids very susceptible:
  Ex: Weeping birch (betula pendula) and Whitespire birch (laciniata)
• North American hybrids are more resistant:
  Ex: Paper, Grey, Yellow, and River birches

What you will see:

• D-shaped exit holes
• Ridges on the bark of the trunk and larger branches
• Dieback from the top down

Life cycle:

• Overwinters underneath bark as full size larvae
• Adult beetles emerge from late May to early June
• Beetles feed on leaves and mate shortly after emergence
• Female beetles lay eggs in bark cracks and crevices
• Larvae emerge, chew through bark, and enter phloem tissue
• Larvae feed on phloem disrupting water, nutrient and carbon translocation

Cultural Management of Bronze Birch Borer

Cultural practices:

• Water tree 2-3 inches per week during summer
• Water 3-4 inches per week during drought conditions
• Mulch tree or treat with Root Enhancement System© with POM, according to Arborist recommendation
• Plant in clumps or where root system will be shaded by other trees or structures
• Do not fertilize without increasing water availability

Chemical practices:

• Bronze birch borer is susceptible to both systemic and topical insecticides