HOME: PSHB - The ‘Cancer’ of Trees

When we first viewed the house we eventually chose to be our home it was the three beautiful trees on the front lawn that captivated us. Large, beautiful, old trees that would come to provide many a shade on sunny days. I remember the previous owner pleading with me to never cut down the middle one and of course I was agreeable because why would we ever want to cut down such a beautiful tree?!

Enter PSHB…

I had never heard of Polyphagous Shot Hole Borer (PSHB) until May 2024. A message was sent in our neighborhood's WhatsApp group alerting residents of a bug that has reportedly infested trees in the area and we were encouraged to inspect our trees for any tell tale signs of infection.

PSHB is a tiny beetle, originating from Southeast Asia that has infested host trees in countries including South Africa, Australia, the United Kingdom (UK) and the United States of America (USA) just to mention a few.

According to Australia's Department of Primary Industries and Regional Development, it is likely that PSHB spread to many countries, including South Africa by 'hitchhiking' via untreated wooden articles and packaging materials. Subsequent spread possibly aided by the movement of infested wood (such as pruned trees or unseasoned firewood).

The beetle tunnels into the tree to breed. The beetle farms a fungus into the tree to feed its larvae, invading the tree's vascular tissues. It cuts off the flow of water and nutrients inside the tree, resulting in the tree dying.

These beetles infesting our trees is of concern in that it kills thousands of trees, I read of one tree that was 300 years old but had to be cut down due to PSHB. Cutting down trees also detracts from the canopy landscape of suburbs and cities and negatively affects property prices.

Specific steps to be taken for infected trees were also included in the text sent on the Whatsapp group. I diligently went about inspecting the trees in our garden, an untrained eye but looking out for the tell tale signs. Relieved, I found our trees to be healthy!

In December 2024 we noticed one of our trees looked different. The bark was stained with what looked like sticky liquid seeping from it. Our then five year old drew our attention to it, describing it as ‘honey’. This raised a red flag as the tree was actually leaking sap…the leaves were falling as though it was autumn - although it was the beginning of the South African summer. The amount of leaves the tree lost was indescribable. Then we noticed the holes on the bark and what looked like running black or navy ink - another tell tale sign. We were worried.

I took pictures of it and went to our nearest nursery. First the woman who assisted me was not too worried by what I had told her until I showed her the pictures. She said "I’m sorry" and we both genuinely felt sad because we knew the reality - we were going to lose a beautiful tree. She put me in contact with an expert who then came out to inspect - he confirmed what we suspected and found another tree in our garden to be infected. Both trees had to be felled (cut down) as there is no known remedy for getting rid of the PSHB. The only known remedy was to cut them down due to how rapidly they can spread from tree to tree, which will result in cutting down of many more trees. There is also safety risk attached to a tree infested with PSHB in that as the tree wallows away it can wilt and eventually fall over, potentially damaging surrounding buildings, cars or God-forbid, people in its direct vicinity.

There is a specific process for felling of and removal of mass infected with PSHB. We, of course followed protocol but there was some confusion. The City of Cape Town (municipality) although they used to, no longer removed infected trees off private property, if it’s within the boundaries of your property, it’s your duty to have the tree cut down and mass removed of in the prescribed manner.

I found a City approved list of PSHB tree fellers. What’s shocking is the cost of having the trees felled and the mass removed. Most tree fellers were ranging from R6000 up to R15,000 to cut down and remove the infested mass. Eventually I found a contractor who would do the job for R3500. He was professional and has been in the business of pest control for over 30 years.

We lost two beautiful trees that day. Trees that took years to grow were gone in 15 minutes.

We plan to replace those trees with trees that are indigenous and not host trees. We’ve been advised that if we plant them now in five years we should have beautiful canopy trees again.

Our tree feller accurately described PSHB as the cancer of trees. The golden lining, because there always is one in every experience, is the opportunity it presents to learn about something new and to plant new (indigenous) trees that are not hosts to PSHB.

Thankfully, I got to keep my promise to the previous owner of our home - the tree in the middle of our garden was not infested and so remains standing and hopefully will for a very very long time.