Bark and Wood-Feeding Insects: Tree Borers
                                     (21 August 2014)

Tree boring insects are a not-uncommon sight on evergreen and deciduous trees and woody shrubs in the neighbourhood. There are lots of different types of borers, many of which attack dead wood only and are therefore beneficial to the garden ecosystem. However, there are also borers which attack live wood with often dire consequences. Some plant genuses are more prone to borer attack than others, such as Acacia, Gleditsia and Albizia (Silk Tree), for example. The occurrence of borers generally indicates health-related stresses including drought, poor soil and nutrition, human interference, or nearing the end of its productive lifespan (i.e. the subject in question has one sizeable bucket well and truly lined up in its sights).

Discovering borers in your garden doesn’t mean you should rush off and purchase the meanest sounding pesticide to douse them with either; in fact, using pesticides in many cases is ineffective and costly. With this in mind, firstly assess the tree affected and consider/observe the following:

• Is the tree a potential threat to your home, person, or that of passerby? A fallen limb from an established tree could cause significant damage to buildings, vehicles and most especially, people. If you are at all unsure, employing an arborist and seeking professional advice is easily the best way to go;
  
• Does said tree look past the point of no return? Are you attempting to rejuvenate a plant that is more dead than alive and any ‘help’ from you is prolonging the inevitable?
  

• Has the tree in question been planted somewhere it shouldn’t have, making it susceptible to pest and disease attack, including from that of borers? Should you consider removing it anyway and replacing it with a more suitable species?
  

 
If you have ruled out the above concerns and would like to persist with and treat your tree for borer, you can try carrying out the following if practical to do so:

 

• Maintain health of tree to highest possible standard by ensuring you are meeting its fertilising, watering, pruning and mulching needs; 
  

• Judiciously prune and remove damaged branches – this won’t be possible if site of damage is located on central leader or sizeable branches of tree;
  

• Clear away frass (chewed up excrement and plant sawdust) from borer site and scoop out borers with a hooked piece of wire or similar. Applying fungicide and filling holes may help prevent fungal attack in some instances;
  

• Or alternatively, if safety is not an issue, enjoy the tree while it lasts then let nature take its course by providing local wildlife with a tasty snack and your mulcher with a sizeable pile of material afterwards.