A problem sufficiently serious that requires the City to transform its
protocol into a legally enforceable document urgently
PSHB is a serious problem and will have major cost and health implications to the City and its citizens. Compliments to a rational article by Nettalie Viljoen of People’s Post, dated 21st Feb 2023: Polyphagous Shot Hole Borer: What does the science say?
According to Henk Egberink of TreeKeepers, Polyphagous Shot Hole Borer (PSHB) is not a new problem. ”The beetle arrived in SA in 2012 and has steadily spread. Almost one year ago, scientists and economists from the Universities of Stellenbosch and Pretoria estimated that the economic impact would be R 275 billion over a 10 year period – and that is very conservative.
Why has this not become top priority?
In terms of tree canopy loss, Cape Town could lose up to 40 % of its large mature trees.
This will dramatically reduce our already very low tree cover of 5.7 % at a time that trees are an essential part for the fight against the negatives of global warming.
However the City seems to be only waking up to this threat now, but I still don’t perceive any sense of urgency.
It is sufficiently serious that we should not rely on the residents and the tree fellers to be the frontline in this fight. It requires for the City to transform their protocol into a legally enforceable document urgently.
In addition I would like to make the following observations: –
- It has become a known fact internationally, that trees under stress have a reduced resistance to the initial infestation and the tree’s possible survival.
The recommended action is to feed and water the tree, starting with a good layer of mulch.
Every gardener should do this immediately.
The City should also act by removing the concrete and tar collars around the trunks of all street trees and mulch. Now is a good time to do this before the rains start.
- The article and the City’s protocol dictates that highly infected trees should be cut down and chipped on the property. Wow… the latter is a recipe for disaster!
Those beetles will leave the tree and get blown all over the place. This procedure should be performed under strictly controlled conditions by competent, preferably registered, contractors. The same would apply to removal in covered trucks of the chips and logs. Solarising in situ may not be practical, considering the time this takes, particularly in winter months. The numbers indicate that there will be a huge number of trees to be felled. Where do we find enough competent contractors?
- Firewood is considered the culprit for the spread of infestation. Make it illegal to move firewood if its source is not known. Gum and pine wood are considered the least likely to become infected. If residents insist on braaiwood, make that type of wood mandatory.
- There appears to be no effective treatment. Research on this should be fast tracked in conjunction with overseas organisations and all available potential remedies should be tried immediately. Even if they don’t work, can they slow down the rate of infestation.
There are several local products, with apparent low toxicity, that claim to be effective. They should be trialled now. If not, why not?
- As trees in the urban forest succumb and die due to the #PSHB infestation, there will be major gaps in the canopy which could lead to infestation by unwanted alien invasive plant species.
This is why it critical to replant and manage the new trees so that the benefits of the urban forest can be experienced universally.”
See here for a list of currently available, suitable trees to replant with, provided by the City.