Newsletter – June 2024 – Protect your trees by David Trope

Newsletter – June 2024 – Protect your trees by David Trope

Polygaphous Shothole Borer (PSHB)

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David Trope
Landscape Guru

Landscape Guru
David Trope

Polygaphous Shothole Borer (PSHB) is an introduced borer beetle from Asia that attacks live wood. It’s killing thousands of trees in Johannesburg every month. It farms a fungus called Fusarium Euwallacea that kills the tree by inhibiting the movement of water and nutrients through the vascular system. There are currently over one hundred and forty species of trees in Johannesburg under attack and we face what can only be described as a national ecological disaster. If you possess valuable, vulnerable trees, you need to take decisive action! Free remote assessment service offered, if you mail through a photograph, or feel free to send a question through.

Research from other countries combined with their established treatment protocols provided us with invaluable knowledge as to how best treat infested trees, as well as prevent infestation of vulnerable trees.

The beetles are too small to detect. However, you can identify the infected trees and do preventative treatments on valuable, vulnerable trees. The symptoms of infected trees vary from one tree species to another and there are several signs that show when a tree is infected.

The holes it leaves in the bark of a tree are extremely tiny. In some species, no holes are visible. Other signs include die-back, wilting, lesions, oozing resin and what looks like a spiders web is residue from the fungus.

There is no silver bullet. Systemic insecticides can take several months to reach the beetles, and injecting trees, which is the most effective method, is expensive. To the best of our knowledge, we are currently one of only two businesses in Gauteng that inject trees with an insecticide and fungicide cocktail.

The strategy for killing the PSHB beetle directly within its host tree is difficult to do, and an effective treatment protocol needs to be accompanied by a multifaceted strategy that incorporates the following:

  • Fight the fungus that the PSHB farm within it tunnels with a non-toxic, environmentally friendly solution, that doesn’t harm the ‘good’ microbes in the soil, or the beneficial insects. Enhance the tree’s health with biochar and thereby boost its own natural defense.
  • Treat valuable trees ASAP
  • Deterrents can be applied to a tree that dramatically reduce the rate of infestation
  • Strategic culling, pruning and treatment needs to be carefully considered, implemented and assessed on a monthly basis until the infested and vulnerable trees are safe. Two years of this should suffice.


If your intention is to save and protect your trees, consider the following carefully:

The trees that seem most vulnerable are London Plane, Oaks, Pride of India, Wild Plum, Mophead, Maple, Paperbark Thorn, Olive, False Olive & Leopard Trees.

Trees need to be treated with a systemic fungicide and insecticide drenching, and then need to receive a follow-up treatment between 2 and 3 months later. The earlier a tree is treated, the better the chances of survival. Preventative treatment is highly recommended.

Trees that are very valuable and those that have a stage 3 infestation are best treated by injection. The cost depends on the number and size of the tree.

Some general advice:

Always seal any wound on a tree with steriseal

Maintain healthy soil, with high quality compost, biochar and mulch

Use Organic fertiliser

Water optimally

If you have an infestation, treat it as quickly as possible

Monitor on a quarterly basis