The City of Cape Town has taken flack following the release of a list of trees recommended to replace those infested with the invasive Polyphagous Shot Hole Borer (PSHB) beetle.
To mitigate the impact of the beetle pest on Cape Town’s urban forest, the City issued a list of 28 trees on Tuesday 4 April “for those residents who want to replace trees on their properties that are infested with the PSHB beetle”.
“If we plant trees to replace those we lose in coming months and years we can limit the impact of this devastating pest on our urban forest,” said Eddie Andrews, Deputy Mayor and Mayco member for spatial planning and the environment.
According to the City, the list of recommended trees includes indigenous and mostly locally indigenous species, that are not reproductive host trees, meaning to date, the PSHB has not been sighted in these trees.
Trees listed include: coastal silver oak, wild pomegranate, num-num, bastard saffron, Cape saffron, atlas cedar, pock ironwood, red elder, Mediterranean cypress, assegai, pom-pom, sand olive, guarri, wild gardenia, Maidenhair tree, sausage tree, bush box, stinkwood, elephant bush, candlewood, willow, white karee, serricea searsia, milkwood, turpentine tree, water pear, camphor bush and fever tree.
Paul Barker, a consulting arborist and PSHB subject matter expert, describes the list as “naive, un-researched and a reckless attempt at an indigenous bias”.
“Most of the listed species proposed will never truly replace the canopy Cape Town is going to lose to PSHB. Many of these trees are unable to be established out of nutrient-rich soil in the moist kloofs of Table Mountain and some are actually reproductive hosts for PSHB,” Barker says.
According to Barker, coastal silver oak, wild peach, wild olive and Cape willow are reproductive hosts. He also questions why rooi els, assegaai, black stinkwood, white karee and fever tree – all trees known to be under pressure from illegal bark stripping – are included in the list.
He asks if this is an oversight by the City or an indication of the lack of consultation with academia, industry bodies and civil society.
“I would have hoped the City would have consulted with experts in the field but they have chosen to arrogantly dictate to the public what they think should be planted and this time they have recommended trees that will not only breed PSHB but will succumb, resulting in further financial loss to the private land owner,” he says.
Posing Barker’s concerns to the City, Andrews says the City compiled the list in-house with the assistance of their Urban Foresters, Biophysical Specialists, and Environmental specialists. He says it was never meant to be a final or extensive list.
“Consultation with interest groups will take place in coming weeks. PSHB hosts were checked against the FABI host site dated November 2022.”
Andrews says the City will update the list as new information becomes available.
“But it is worthy to note there will be differing views on this topic across the board, regardless.”
He adds that the list provided by the City also takes into account the potential fire risks posed by some trees.
“Those regarded as invader species, and those prone to the PSHB that we are aware of, being mindful that some trees actually do have a resistance to PSHB, and can survive an infestation.”
Andrews confirms that Kigelaria Africa is a reproductive host “and should not be planted with current information available”.
“Wild olive and Cape willow are hosts (only) but should survive PSHB infestation,” says Andrews.
As to bark stripping, Andrew says it is a real but limited threat.
“By planting these species we may oversupply the stripping market and save some of our trees,” he adds
The media release sent out last week advises residents that they should also ask their local nursery, arborist or landscaper for more detailed advice.
“As we cannot address the unique environmental circumstances of every private property in a media release. Thus, the list is a guide only, and depending on where you live, some trees may be more suitable than others,” says Andrews.
The media release also refers residents to the City’s online Tree Best Practice guideline which provides more information about trees suitable to Cape Town’s climate.
However, Barker claims that when he went to a prominent retail nursery in an area with a confirmed PSHB infestation last week, he found 20 reproductive host trees for sale.
- Find the City’s Tree Best Practice guideline online at: https://resource.capetown.gov.za/documentcentre/Documents/Procedures%2c%20guidelines%20and%20regulations/Green_Infrastructure_Programme_%20Trees.pdf
