The infestation in the Southern Suburbs of Cape Town cannot be stopped or contained, there are no licensed treatments for PSHB nor any peer reviewed studies showing that any treatment is effective.
The disease can however be slowed. Its breeding sites can be removed. By a huge margin, Acer negundo “ Box Elder ” a common species of maple, is an amplifier of this disease. The beetle prefers it to any other species. By removing this species from your property you are removing the most potent lure from your property. I would advise this as the most effective step you can take at this point to protect your other trees, and your community’s trees. The City of Cape Town’s parks branch has undertaken to fell Acer negundo’s on their land but are not allowed to assist with trees in private land. The waste arising should not be burnt, but should be chipped, this kills most of the beetles, and covered with black plastic to solarise and kill the survivors. If the material must be moved, it should be transported in a closed vehicle to an incinerator plant. Please don’t move firewood or plant material out of this area unless you are sure that it is not from an affected species. Eucalyptus (Gum) is safe.
Google FABI PSHB for a list of reproductive host species and affected species. Reproductive host species should not be planted, and existing specimens should be inspected regularly. Affected species are trees that the beetle entered and failed to breed in. They can still be planted and are of least concern.
Take a chisel or knife and cut back the bark until sapwood around the borer entry point is exposed, 2.5×2.5 centimetres or similar. One third of the way of the taper into Xylobours 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/Euwlacea fornicates. All the way in is platyplodonae an indigenous lookalike. Attacks weakened and stressed trees.