Cape Town - Locals are warned to brace themselves and unite to fight against the spread of an invasive beetle while the City of Cape Town is still figuring out the best approach to tackle the outbreak.
It’s been a month since Cape Town reported its first sighting of the invasive polyphagous shot hole borer beetle (PSHB) which has since widely spread, affecting box elders and oak trees in different suburbs in the metro. Experts say the species is here to stay.
Francois Krige, an arborist and chair of Friends of the Arderne Gardens (FOTAG) I’m at the, said if the mismanagement of the spread persisted the metro would stand a risk of losing up to 40% of its trees. He said within the variety of trees found locally, FOTAG research discovered that about 27 species may be affected, both the indigenous and alien trees.
He said as dangerous as this beetle is, human behaviour may play a bigger role in spread.
“It must be noted that beetles cannot move far on their own, they can only fly about 500m a year, which would make one assume it’s unlikely to spread far. But if our people are not well informed, there are no regulations and the handling of the removals is not well monitored.
“We implore the City of Cape Town to have a conclusive plan to address this issue before it gets out of control. It's another pandemic hitting us...I choose preventive measures rather than wasting time on research and spending funds while the problem continues to grow bigger.”
Krige added that there’s no scientifically proven treatment for the spread.
“I am in favour of felling infested trees, 95% of infested trees in the southern suburbs are Acer negundo. I recommend pre-emptively felling uninfested specimens in the close proximity of the zone of infestation.”
Krige also said that cutting the tree before infestation was cheaper than when its considered a risk.
Mayco member for spatial planning and environment, Eddie Andrews, confirmed that a total of 128 infested trees have been recorded in Newlands, Rondebosch, Mowbray, Claremont, Observatory along the Liesbeek River, and in Kenilworth.
“The City is still in the process of finalising the budget across multiple directorates to deal with this challenge.
“We are on the lookout for research that is being done in other countries that have also been hit by the PSHB invasions. Internationally, there are scientific researcher looking at potential use of parasitoids, pathogens or antagonistic fungi as potential biocontrol agents for PSHB,” Andrews said.
He said they are also working with Stellenbosch University’s Department of Entomology, and have access to information from Fabi on research work being conducted in other parts of the country.
Professor Francois Roets of the department of Conservation Ecology and Entomology at Stellenbosch University confirmed that research is under way to find a biological control agent for the fungus and the beetle.
“It’s safe to say, however, that more money has been spent on cutting down infested trees and in the application of ineffective control measures than on research on this very difficult pest.”
Roets revealed that a concerning spread is being noted in the Somerset West region as well, where the PSHB was initially noted and has been controlled since 2019.
“We have now confirmed the presence of the beetle in multiple suburbs of Stellenbosch two weeks ago, but knew about its presence in Onder Papegaaiberg and Die Boord since last year.
“The very first dead box elder trees were noted in Onder Papegaaiberg at the beginning of this year and, more problematically, the very first oak tree that was killed by PSHB was found in central town last week. Many tree individuals around this tree are however showing signs of initial infestations and our predictions are that at least 15 000 trees will eventually die here unless we can find a workable solution soon,” he said.
Dr Caitlin von Witt, Fynbos Life Programme Manager, said they are worried that although Cape Town is a fynbos city, with only 0.4% of Southern Afrotemperate Forest occurring within city borders, the PSHB could nevertheless have a devastating effect on our small natural forest species and on large numbers of planted trees.
“If these are threatened by PSHB, we stand to lose important urban oxygen factories and carbon sinks. This invasion is a public problem that we can only address effectively if private landowners or residents contribute by sharing locations and being actively involved in the attempted eradication process.”