Cape Town - As Cape Town’s infestation of the invasive polyphagous shot hole borer beetle (PSHB) continues to spread and endanger urban forests and local gardens, the Friends of the Arderne Gardens (Fotag) in Claremont raised concerns that the outbreak in the Southern Suburbs posed the gravest threat their arboretum has ever faced.
The City warned that the tree-killing beetle could easily spread across suburbs if extra precautions were not taken. The impact of the infestation on Cape Town’s trees is expected to be monumental.
The City previously said it could lose 1 million of its 4 million trees to PSHB in the next decade.
Arderne Gardens in Claremont has one of the most diverse and valuable collections of exotic trees, including one of the largest trees in South Africa, the vast Moreton Bay fig (or Wedding Tree), and possibly the largest Aleppo pine in the world.
Fotag chairperson Francois Krige, an arborist with 35 years’ experience, said they were incredibly concerned about the proximity of the PSHB in the Southern Suburbs as it posed perhaps the greatest threat to the arboretum at Arderne since the original trees were planted in the 1850s.
To combat this outbreak and its impact on the heritage site, Fotag is making use of their skilled and experienced team, who are working on a management plan tailored specifically for this garden. This is influenced by recommendations from academic experts on the matter.
“It is a challenging site as there are many rare species. There are also some of the most iconic and well-loved trees in Cape Town. We are investing heavily in verbenone repellents, hanging masses of them in the champion trees that are vulnerable, then lures and traps are to be deployed around the perimeter,” Krige said
He said they also planned to pre-emptively remove Acer negundo within the garden along with a few other low-value reproductive host species.
Acer negundo accounts for more than 90% of infested trees in the surrounding area, and 100% of the outlier species as well as 100% of the severely infested species.
“They are referred to as ‘amplifier’ species. To borrow from Covid-19 terminology, they are the super spreaders of PSHB. This will all be funded by FOTAG and its donors. The City has given us their blessing. Given the absolute urgency of this project, we are planning on commencing with the removal of low-value reproductive hosts next week,” Krige said.
Deputy mayor and spatial planning and environment Mayco member Eddie Andrews said: “This is a very small beetle, but the potential damage is at scale. I am urging residents to be on the lookout for symptoms, and owners of nurseries and landscapers should do the same. We cannot afford to be complacent.”