Shot-hole borer beetles are as tiny as sesame seeds, but they are laying waste to forests around the world. And it takes only one female beetle to move from Somerset West to Kirstenbosch to start a new colony.
This is according to ecologist Dr Francois Roets, of Stellenbosch University. “The problem is massive and spreading towards Cape Town,“ he says.
He believes the beetle could cost the country R275 billion over the next 10 years. “Most will be municipal problems as trees become dangerous to people and properties.”
Phumudzo Ramabulana, of the City’s invasive species unit, says the beetles have not been found in the heart of Cape Town yet, but this does not mean they’re not here already.
Dr Roets and Mr Ramabulana were among speakers at a presentation hosted by the City at the Somerset West Town Hall, on Monday June 22.
The polyphagous shot-hole borer beetle arrived at Richard’s Bay Harbour – probably in pallets – in 2017. Since then, scientists have found at least three more species.
Debbie Muir, specialist programme manager at the Department of Forestry Fisheries and Environment (DFFE), said the beetle would be registered under the National Environmental Management: Biodiversity Act, as a 1a invasive, which means it must be removed by the owner or user of the property on which it occurs.
“Plans must be submitted to the ministry on a species-management plan of how it will be removed. We will give assistance, but, ultimately it’s the responsibility of the property owner/user,” said Ms Muir.
The beetles crept along the coast, infecting trees, before arriving in Somerset West in 2019.
Somerset West resident Gigi Steenkamp spoke of the emotional pain of having to remove trees from her large garden, saying if it continued the suburb would resemble a desert.
Dr Roets said at present there was no answer to eliminating the problem. “So early detection and possible treatment is vital, versus the protocol of simply felling all badly infested trees. The costs accompanying this are enormous, as are the urban and agricultural implications.”
He said the beetle had become a global citizen, from Southeast Asia and Taiwan to Israel, Perth and California.
The beetle is called “shot hole” because of the way it drills into wood. “It carries a pathogenic fungus (Fusarium euwallacea) into the tree, and that’s what the beetles eat. What you see is a hole, inside is a network of tunnels. Insecticide, fungicide can’t get to it,” said Dr Roets.
The beetles travel on pathways of rivers, movement of infested firewood, dumped wood and fresh wood chips. “People make a living from selling wood chopped down from trees; we can’t stop it,” said Dr Roets.
Ms Muir said that the problem with using pesticides was that they affected bees.
Faye Crankshaw, the spokeswoman for the Helderberg Tree Conservation Group, took this reporter to see trees on public land and gardens. At Jenny Stidworthy’s large property, a Kei apple tree had been treated with an over-the-counter surfactant, which helps insecticides penetrate the tree bark and reach the beetles in their tunnels. Ms Crankshaw said it is registered in South Africa soon and the registrar to extend its registration which expired in May.
Ms Stidworthy also has a home-made trap in her garden that monitors if the beetles are in the area.
Ms Crankshaw said every tree presented differently and she pointed out a box elder covered with tiny holes and a bladder nut oozing black gum.
Dirk Bellstedt, a biochemist at Stellenbosch University, showed a stand of heavily infested poplars on public open space at Companjie Road and Harewood Avenue. We then saw an avenue of Turkish oaks planted in 1850, most of them now infected by beetle.
Dr Luke Potgieter, a conservation officer at the City’s invasive species unit, said trees cut down were chipped on-site into a closed truck on a plastic sheet and afterwards the chipper was cleaned.
Julian Ortlepp, an arborist and member of the Johannesburg Urban Forest Alliance, said Capetonians were in the emotional phase about trees, where Gauteng had been in 2016. “We are now in realistic phase where trees are being removed. It’s a disaster with biomass – the movement of wood. In Johannesburg, removed trees were taken 20km outside the city. Now the entire route is a hot zone. You’re in the phase to be proactive. The government takes too long. Do not move your wood around. Do chipping at the epicentre,” he said.
Dr Potgieter said “amplifier” trees, those that are good hosts for the beetle, included box elder, London plane and English oak. Aromatic, resinous trees such as conifers pin oaks and gums are more resistant.
DFFE chief agricultural food and quarantine technician Baikanne Phologane said R11m had been spent so far, mostly on chipping the 2 000 trees cut down in Somerset West.
Ward 84 councillor Norman McFarlane said the presentation was called because of a lack of trust between the City and citizenry. He said that Somerset West was the epicentre of infestation. “It’s up to us to build a wall and keep it out of urban forests,” he said.