Let’s save our trees! Shothole Borer

Gardens are under attack by an enemy that we can barely see. Arm yourselves with this valuable information and be ready to go to war!

Over 200 tree species are under attack by a tiny, nasty little tree killing borer beetle with a mouthful for a name; polyphagus shot-hole borer beetle, (or PSHB). The beetle, which is only the size of a sesame seed, creates tunnels deep into the tree where it reproduces and infect the tree with a fungus which in turn becomes the beetles’ food source as it eats the fungus.  This fungus grows from the tunnels into the tree, harming it and can kill full grown untreated trees within a few seasons. The trees it infects include both indigenous and exotic species including some fruit trees such as avocados.

What to look out for:

Since the shot-hole borer is so small and often not seen, it is easier to look for signs of infestation. The symptoms vary from one tree species to the next:

  • Wilted leaves or shedding of leaves
  • Dead or dying branches
  • Tiny, pen-tip sized holes randomly spaced in the bark
  • The holes may have stained marks around them, or have white sugary powder, (known a sugar volcanos), or even gummy beads oozing out of the holes, or most likely “sawdust” on the tree and below it on the ground.

To view images of infested trees: PSHB.co.za/pshb-tree-identification/

To view the beetles: PSHB.co.za/pshb-beetle-identification

What can I do to protect my trees?                                                                                        

The good news is that not every tree will be suitable as a host for the beetle. Strong, healthy trees are less likely to be attacked and if infested, will withstand an attack better. You can boost the health of your trees by:

  • Mulching the tree’s root area
  • Water sufficiently
  • Add nutrients to your trees via fertilizers, composts and manures, (ask your local GCA Garden Centre for advice).
  • Introduce microbe stimulants to the soil around your trees to improve the soil and thereby the tree’s health and vigour, (again, ask advice from your local GCA Garden Centre).
What can I do to save my infected trees?

A fungicide has been developed that will eradicate the fungus, save the life of the tree and starve the beetle of food, often killing it too – enquire at your local GCA Garden Centre. (A surfactant, which helps insecticides penetrate the tree bark and reach the beetles in their tunnels will hopefully be registered in South Africa soon. To keep abreast of these developments, check for up-dates on the various PSHB websites).

Be responsible:

Just one heavily infested tree may contain over 100,000 beetles, therefore we need to:

  1. Spread the word via social media and word-of-mouth to our neighbours and communities if we find infected trees, since the risk to healthy trees from those already infected is very high and the female beetle can fly up to 1 km infecting suitable surrounding trees.
  2. Quickly dispose of infested trees parts or dead trees in a manner that prevents the beetle spreading further. Dead trees can remain as a breeding ground for up to a year. Find excellent solutions at https://polyphagous-shot-hole-borer.co.za
  3. Sterilize any pruning equipment or wood-chipping equipment that comes into contact with infected wood.
  4. Do not transport wood or fire-wood from one area to another without being sure that it is not infected or has been treated.
  5. Be part of the solution by reporting infested trees. Go to jufa.org.za/pshb to acquire the information that you will need to email to pshb@fabi.up.ac.za. A Tree Survey app can also be downloaded from Google Play or iTunes. A user guide is available at TreeSurvey.co.za/how-to-guide/

For more gardening tips and information, visit www.lifeisagarden.co.za  or join the conversation on our Facebook page: www.facebook.com/lifeisagardensa.

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