PSHB FAQs
As of the end of summer 2025.
The beetle has spread quickly through the southern suburbs, from Bergvliet in the south to Woodstock in the north, the M5 in the east and into the eastern parts of Constantia and Bishopscourt.

Box Elders
If you have a box elder (Acer negundo) within this area, we suggest that you remove it. They can be considered “super spreaders” of PSHB. They have zero resistance, and the beetles breed very rapidly in them and then disperse to less favoured species. We have literally seen the disease leapfrog through the suburbs from one box elder to another.

Oaks
If you have a European oak tree, (Quercus robur), within the infestation zone, it is likely to be harbouring some beetles already. The entry holes are hard to see on oaks, but the effects of the beetle and its fusarium fungal associate is quick to show up in the form of parts of the tree browning off and dying.
European oaks also rapidly become very brittle, dangerous to safely climb and rig down, and pose a hazard to people and property under them. Please take action quickly and fell them once they are infested, but before they become dangerous.
Do not let sentimentality or false claims of “treatment “or “cures” deter you from taking reasonable precaution.

Other species of oaks
Many other species of oak are either resistant or experience a bit of nibbling from the beetle. These trees should be monitored, not felled. If the infestation gets bad because the specimen is vulnerable due to a pre-existing condition, have it inspected, and its management can be decided on.

Plane trees
Plane trees (Platanus acerifolia) are very susceptible and it’s very easily identified, weeping drips on the trunk and lower crown, usually between 2 and 4 metres from the ground. These trees can sustain heavy infestation for some years and not die, some will succumb, and others may survive. Long horizontal lateral limbs will become brittle and dangerous. Let us inspect the tree annually and we can prune it as needed.

Coral trees, (Erythrina afra)
These are very susceptible and quickly become brittle and show signs of dieback. Lateral limbs should be removed or shortened to keep them safe. Coral trees may well die from PSHB.

Other species.
Here is the South African list, and a global list.

   

Many other species are susceptible and can have breeding populations of beetles within them. It does not mean that we should not plant these species, or that we should fell them simply because they are infested. Many will survive even though beetles breed in them (reproductive host species). We recommend annual inspections, especially if it is a large tree that can pose a hazard to people or property.

Finally, there is a very long list of trees that get a nibble from the beetle, but she fails to breed in them, she either dies or exits the tree, (affected species). These trees are like us humans who caught covid and survived, it’s a good indicator of a healthy tree that it got nibbled and survived. Keep planting those species.

Treatments and cures
There have been some attempts at slowing down the spread of the beetle once it’s in the tree, using insecticides, fungicides, or combinations of both.

At best the breeding of the beetle has been slowed down, but this has not yet been demonstrated with proper trials. What has been apparent after various studies is that this incredibly invasive beetle is able to spread in the heartwood of trees, beyond the vascular system, so beyond our systemic root treatments, trunk injections, foliar sprays etc. By making the tree completely toxic it is theoretically possible to slow down the disease, but temporarily, and at huge cost to the environment and the owner of the tree.

I have never seen so many businesses come out of nowhere, with people who have no track record in our profession, claiming to have a solution to the infestation. There is a huge market for this as tree owners are understandably upset at losing their trees. We at Krige Trees take no pleasure in this situation, I would leap at any treatment that showed promise, so far none do.

I am fairly sure that if someone was conscientious enough to monitor their tree throughout summer when the beetle is dispersing, and trained them self to spot the entry holes, they could kill the beetles while they were still shallow in the wood. This would not work on European oaks, as the holes are not easily spotted, but on smooth barked trees, it would theoretically be possible to inject the entry holes with a hypodermic syringe filled with a product like Rosecare, insecticide and fungicide mixed. If this mix made contact with the beetle before she has time to make galleries deeper into the tree, she would undoubtedly die.

Obviously, this is not the sort of service that a commercial tree company can offer, but it’s worth mentioning. The problem is that this would possibly be something that would be necessary for many years to come. We simply don’t know what will happen to beetle populations when the favoured hosts are off the landscape.

Please plant trees.
We stand to lose so many trees in the next decade. We have the option of planting trees. I believe we should do so.

Identifying PSHB
A good way to identify PSHB is the toothpick test.
PSHB is one of a very few beetles that infest green parts of the tree trunk or branches. Take a chisel and cut back the bark until sapwood around the borer entry point is exposed, 2.5 x 2.5 centimetres or similar. Take a standard toothpick.

• One third of the way of the taper in is Xyleborus perforans. There is often a purple stain around the hole. This is an indigenous species that targets sick and stressed trees only.
• Two thirds of the taper inserted before it gets stuck is unfortunately PSHB/Euwallacea fornicatus.
• All the way in is Platypodinae, and indigenous lookalike. Attacks weakened and stressed trees.