Residents are being encouraged to participate in a voluntary tree replacement programme as the removal of Polyphagous Shot Hole Borer beetle (PSHB) infested trees from public-owned land moves ahead.
Eddie Andrews, the City’s Deputy Mayor and Mayco member for spatial planning and environment, planted the first replacement tree – an Assegai tree (Curtisia Dentata) – along the Liesbeek River in Mowbray on Friday 10 March. The City is currently busy removing trees infested with PSHB in this area.
“As far as we know, the Curtisia Dentata is not a reproductive host tree, meaning, to date, the PSHB has not been sighted in these trees which makes it a good replacement choice,” says Andrews.
The City is working on a comprehensive list of recommended trees – indigenous and mostly locally indigenous – that residents can plant to replace those trees that will have to be removed because of the beetle pest.
Besides the Assegai tree, the City recommends White milkwood (Sideroxylon inerme ), Camphor bush (Tarchonanthus camphoratus) and Water pear (Syzigium quineense).
Andrews says the comprehensive list will be available, and added to, on the City’s website in coming weeks.
“Residents can use it as a guide to participate in a voluntary tree planting effort. In the meantime, we are finalising our official tree replacement programme to replace those infested trees we have to remove from City-owned land,” says Andrews.
The City started removing infested trees along the Liesbeek River corridor, near the N2 highway and Liesbeek Park Way, with chainsaws and wood chipping machines on Wednesday 8 March.
According to the management protocol drawn up by the City’s Invasive Species Unit, the priority is the swift identification and removal of highly infested trees to reduce the beetle population. Infested trees must be chipped on site.
With the use of pesticides and fungicides having shown a limited effect to date, researchers say the removal of infested trees remains the best bet in efforts to slow down the spread of PSHB (“Polyphagous Shot Hole Borer: What does the science say?”, People’s Post, 21 February).
“Unfortunately, infested trees have to be chipped as this is the only scientifically proven method to prevent the spread of the pest to other areas in Cape Town,” says Andrews.
While commending the City for promoting a replanting programme to compensate for the loss of trees, Clare Burgess, chair of TreeKeepers, says such a programme will need to be managed and monitored for effective use of funds and choice of suitable tree species.
TreeKeepers is a citizens’ organisation that works to conserve trees in the urban forest.
“We doubt that the idea of only replanting with indigenous trees is going to have any impact or benefit for the urban forest and suggest that other tree species such as Pines and Gum trees are also considered as suitable replacement species,” says Burgess.
She adds that there is also a concern that, if a tree is correctly identified as hosting PSHB, it may be removed in a way that will further spread the borer and associated fungus.
“This is because the approved method of dealing with the issue involves a team of workers, machinery, chipping and solarising mulch and all this requires considerable funds and space, which is in short supply in an urban forest situation.”
Burgess says that the way forward should include a protocol that documents the methods that can be used to deal with this threat, including the possible use of pesticides and fungicides.
“Data must be collected so that proper analysis can be carried out. It is very sad to hear that in Johannesburg there has been little or no monitoring of the disease as it spread through the City and no one can tell us how many trees have been impacted,” she says.
Riaan van Zyl, an arborist and a member of TreeKeepers, says political representatives, councillors and officials are not communicating with those with alternative views.
“Even if they are scientists. It’s time to do so.”
He believes oversight is lacking in what he describes as a “kneejerk reaction” by the City.
“There is no public participation or consultation with any civil organisation when applying this felling policy. They simply go ahead. Very strange and not characteristic of a democracy,” says Van Zyl.
According to a study published last year by the Centre of Excellence for Invasion Biology (CIB) at Stellenbosch University, the potential economic impact of PSHB in South Africa will amount to R275 billion over the next 10 years if nothing is done to stem the tide (“Invasive beetle to hit municipalities and property owners where it hurts”, People’s Post, 14 February).
Van Zyl argues that the felling and removal of “living trees” will be an extra cost to the City.
“For which there is no budget. These direct costs of felling were not calculated in the above loss assessment for values and functionality contributed by living trees to be lost. It must be noted that operational tree felling and removal will be exponentially more than the loss assessment. Where is the money going to come from?”
Earlier this month, the City hosted two PSHB training sessions – at Muizenberg and Helderberg Nature Reserve in Somerset-West – for small businesses dealing with plant material. Andrews asked residents wanting to have PSHB-infested trees removed to use gardeners and local businesses familiar with PSHB protocols.
“And don’t fall for fake remedies. There is no known cure as yet,” says Andrews.
