What is the Bronze Birch Borer?

Pests and Diseases

15th April 2020 | Info

Common Name: Bronze Birch Borer 

Scientific Name: Agrilus anxius 

Origin: North America 

Introduction: The Bronze Birch Borer is not currently in the UK; however, they could have a significant impact on our native birches, so it is important that we familiarise ourselves with this pest. 

What is the Bronze Birch Borer?

The Bronze Birch Borer (also known as the Jewel Beetle) is a tree pest that commonly affects Birches.  They are a metallic bronze colour – hence the name – and quite small. 

In their larvae stage, Bronze Birch Borers feed on the wood of a tree, in turn creating galleries which make it harder for the infested tree to take up its necessary water and nutrients. 

Once they mature and develop into adult Borers, they become strong fliers, meaning that they can spread very quickly.  

Where are they currently affecting?

Bronze Birch Borers are mainly present in their native country of North America. 

However, because Birch trees in North America have adjusted and evolved with the beetles, they appear to be less susceptible to the dangers of the beetle and have fewer issues with them.  

Why should I be concerned?

UK and other European Birch trees are incredibly likely to, and most probably will be, more susceptible to the dangers of Bronze Birch Beetles as they have not evolved around the pest if they were ever to make their way to Europe. 

This could have a catastrophic impact on our native Birch Trees which is why it is important to make ourselves aware of the symptoms, but also take necessary precautions when importing Birch trees too.  

What should I look out for?

Symptoms that Bronze Birch Borers are present are: 

  • Discolouration or thinning of the crown 
  • Epicormic growth on main stems and larger branches 
  • Rust coloured sap from swollen welts on bark – caused by larvae eating through wood. 
  • D-shaped holes in bark – caused by adult details emerging through the bark once they have completed their full life cycle. This is one of the main telling signs that your tree will almost be dead. 

How can we avoid it?

To help reduce the risk of Bronze Birch Borers making their way to the UK, certain measures have been put into place. 

It is currently illegal to import Birch trees from the US and Canada – and all Birch trees that are imported must be from Bronze Birch Borer-Free countries.  

Rules even extend to imported wood where any wood that is important from North America must have its bark stripped and have 2.5cm of sapwood removed. 

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