Borers are a destructive insect that causes terrible damage to trees and shrubs. They are particularly pernicious in South East Queensland due to our subtropical climate. A borer infestation can be very difficult to control and can often lead to devastating consequences. These consequences may include the loss or forced removal of a tree and the infestation of neighbouring trees as well.

The good news is that, with early spotting and professional advice, borers are able to be eradicated and controlled.

Life cycle of a borer

Boring insects cause damage to woody shrubs and trees as they hatch from eggs. Pupae borers use the host as food; the richest and most desirable source of food for a borer is the cambial layer of the tree. This layer is the mechanism the tree uses to transport nutrients and water to all parts of the plant, therefore when borers start eating and destroying this layer, the effects to the plant are swift. Sometimes a tree that is infested with borers can die within just a few weeks of the initial contact.

Adult borers emerge from the tree in the warmer months of November and December, mate and lay their eggs on the bark of the tree. As the larvae hatches, the pupae are commonly recognised as grubs. The pupae of the Longhorn Beetle are known in Australia as witchetty grubs.

As much of the life of a borer takes place inside the tree, they can be difficult to spot until the adult bugs are noticed in the garden.

What borers are common in South East Queensland?

In South East Queensland there are two borer species that cause the most of the damage to our local flora; they are the Longhorned Beetle and the Poinciana Borer.

The Longhorned Beetle borer is an Australian native insect and is often called the Eucalyptus Longhorned Borer. This insect attacks susceptible eucalypts and is also known as a pest throughout the world where eucalypts have flourished, such as in California.

How to spot a Eucalyptus Longhorned Borer

  • Found in eucalyptus trees
  • Adult beetles are approximately 25mm long
  • Adults are a dark red with a yellow abdomen
  • More information is available here 

How to spot a Poinciana Borer

  • Found in Poinciana, Figs and Pecan trees
  • A large (60mm long) brownish beetle with long antenna, jaws and pointed teeth
  • Can bite
  • More information is available here

How do I prevent borers?

As always in horticulture, prevention of a pest or disease is better than cure. This is especially true when it comes to borers. If you have eucalyptus, poinciana, fig or pecan trees you need to be constantly vigilant for evidence of the infestation.

Keep an eye out for the signs of borer activity in your garden; 

  • Entry holes
  • Audible gnawing sounds coming from trees
  • Discolouration of leaves
  • Unexplained crown dieback
  • Wilting foliage

Keep in mind, borers are attracted to plants and trees that are already stressed. Keeping your trees healthy, well watered and fertilised will go a long way in borer prevention.

How do I treat a borer infestation?

Borers are dangerous insects to your plants and landscape, they can cause significant damage and spread from tree to tree quite quickly therefore any evidence of borer activity needs to be taken seriously.  There are a number of different techniques to get rid of borers however it is important to get the consultative and diagnostic services of an experienced arborist to determine the extent of the activity.

Insecticides tend to have a limited effect on disrupting the lifecycle of borers and can do more damage to the tree and surrounding landscape, so best to avoid a pesticide fix as the first course of action.

At Kings Landscapes, we have been treating and eliminating borers for the last 50 years. We understand how borers interact with our local environment, tree species and climate and can develop solutions for your infestation. Get in touch with our team as soon as you see evidence of borer activity in your landscape.