This has been described as a potential disaster with the collapse of the city’s ecosystem collapse of up to 70% of the city’s 10.2million trees die. Joburg City Parks and Zoo (JCPZ) said because the borer infestation was relatively newly discovered, there was very little data available.
Worldwide, even countries like the US have no known remedy.
Adelaide Chokeo, JCPZ’s arboriculturist, said many countries had their own strain of the beetle and no one has come up with international solutions.
The JCPZ this week held a walkabout in Illovo to demonstrate the affected trees which are being monitored. Chokeo said the trees were scanned and recorded and marked with red dots if they were infested.
“We won’t be cutting down infested trees at this stage, only dead ones and we advise residents to do the same. We need to monitor them to see how long it will take for them to die, so we have records. Also many of the plane trees affected have already reached their lifespan, so this is just speeding it up,” she said.
About 24 trees in Birmingham Avenue, Craighall, were to be felled within the next few weeks. The lack of information is leading to this environmental crisis, added Chokeo.
“We have other species of trees growing right next to infested ones which are healthy. We are also propagating 4000 saplings in our Linksfield nursery which we are monitoring and, when we get the results, we will be replanting the ones we have felled.
“Even the University of California has been investigating this crisis since 2003, but has not come up with a solution. Also, worldwide we are undergoing climate change and we’ll have to record this to see how it is affecting the infestation,” she added.
“There is no chemical control allowed as this will affect the bird and insect life which is critical to the ecosystem.”
City parks is also investigating the resistant trees, reproductive and non-reproductive trees which reproduce the infestation.
JCPZ said trees cannot just be felled. A process called solarisation is used, which means that, once felled, the dead wood is covered with a tarpaulin or plastic cover to kill the beetle, which can take up to six weeks depending on temperatures.
In recent weeks the Johannesburg Urban Forest Association organised four tree walks in the worst-affected areas such as Craighall Park, Hurlingham, Parkview and Parkhurst to explain the PSHB crisis.
JCPZ is organising an open day at the Zoo Lake Training Centre for March 11 to explain how to identify and responsibly dispose of dead wood affected by the PSHB. Residents are urged to report diseased trees by emailing [email protected] with the location of the tree.
The list of infested trees compiled by the Forestry and Agricultural Biotechnology Institute in Pretoria is on the JCPZ website, www.jhbcityparks.com.@annacox