PSHB Treatment Guidelines

The Polyphagous Shot Hole Borer (PSHB) has arrived in South Africa and it is devastating our trees. Research from other countries combined with their established treatment protocols provide us with invaluable knowledge to fast-track our national response, which can improve the outcomes for our urban and ingenious forests.

Under Act 36, chemical products need to be registered for use against specific pests, and as such some local manufacturers have started to apply for registration using emergency registration procedures. Whilst the strategy for killing the PSHB beetle directly within it's host tree is enticing it is difficult to do, and an effective treatment protocol needs to be accompanied by a multifaceted strategies that adopts the following elements:

  • Fight the fungus that the PSHB farm within it tunnels
  • Enhance the tree's health and thereby boost it's own natural defenses. Some trees may be capable of compartmentalizing existing damage, whilst new growth is critical to recover vitality thereby increasing the trees chance of survival
  • Deterrents can be applied to a tree can reduce the rate of natural infestation, and beetle traps can draw PSHB away from trees whilst reducing the population.
  • Strategic culling and pruning needs to be carefully considered as treatment against PSHB will likely need to be repeated on a cyclical basis. The cost benefit of treating ornamental trees needs to be carefully considered.

 

In the past year since PSHB was formally identified within South Africa, a lot has been learnt about tree mortality and the outcomes of various combinations of treatment amongst urban trees. Whilst some genus of trees are displaying resilience intense infestation, and others genus are dying almost on a predictable basis, exceptions do occur which will inherently prevents the representation of a treatment protocol that is guaranteed to save every tree. At best the collective efforts of the South Africans who are trying to develop solutions to fight PSHB will iteratively contribute knowledge ,practical techniques and products that can be used to improve our tree outcomes.

 

If your intent is to save your tree, consider the following carefully:

  • Is your tree actually at risk, and have you verified that beetle activity in your garden or suburb is infact PSHB. The PSHB beetle holes in the bark of a tree are extremely tiny, and they only attack living wood. If you are uncertain ask a local arborist for advice or request assistance by submitting photos of your tree using the Tree Survey Mobile App. 
  • Many trees will not suffer sever infestation since they are not optimal hosts for the beetle, it is likely that you do not need to treat these trees, or at most you should focus you effort on just enhancing these trees health.
  • Some service providers (gardeners, landscapers, arborists, tree fellers) with engage with you ethically, whilst others might prove to be opportunistic. Familiarize yourself with market pricing, and recognise that there is no silver bullet to this problem - don't allow emotional purchasing decisions to cloud your judgement.