Cape Town - After the province’s first discovery of the tree-killing Polyphagous Shot Hole Borer (PSHB) beetle infestation in Somerset West three years ago, the full extent of the beetle infestation in the province remains unknown but has since spread to Bitou, George, Knysna and most recently in Stellenbosch.
Local Government, Environmental Affairs and Development Planning MEC Anton Bredell said scientists estimated 30% of urban trees were susceptible to the beetle and as such Cape Town could lose a million of its four million trees to PSHB in the next decade.
“This could generate as much as 10 million decimal cubic metres (DCM) of infested green waste and firewood that requires handling and safe disposal. The only agricultural affected area in the province is the Helderberg, where PSHB has infested avocado, pear and plum orchards,” Bredell said.
Bredell said approximately 10 000 trees would be infested in the Helderberg area by the end of this year but numerous measures were being implemented to address the potential damages caused by the beetle.
Bredell said the Department of Agriculture, Land Reform and Rural Development was actively monitoring the spread and convened the PSHB Steering Committee under the Plant Protectorate – which included monitoring from the City’s Invasive Species Unit.
The Department of Forestry, Fisheries and the Environment was also waiting for ministerial approval to have PSHB classified as a Nemba 1b invasive pest, which required a compulsory invasive species control programme to remove and destroy the species.
“In addition, trapping is currently undertaken by Stellenbosch University together with the Forestry Agricultural Biotechnology Institute (Fabi) who are actively monitoring in Wilderness, Kirstenbosch and Helderberg areas. Kirstenbosch has had no interceptions to date,” Bredell said.
University of Pretoria Fabi research fellow Trudy Paap said as trees succumbed to infestation by the PSHB and its fungal symbiont, falling trees and branches in urban and peri-urban environments may affect human safety and damage vehicles and infrastructure.
There would also be considerable costs associated with tree removal and substantial environmental impacts.
Spatial Planning and Environment Mayco member Eddie Andrews added that the City recorded over 3 500 trees affected by PSHB in Somerset West.
“All English oak, boxelder and London plane trees, among others, are under threat. These three species account for most of the trees affected in the Somerset West area and the likelihood is that they will all die because of PSHB,” Andrews said.
