The comprehensive presentation by Dr Wilhelm de Beer from FABI (Forestry & Agricultural Biotechnology Institute) about the Polyphagous Shot-hole Borer was attended by representatives of SANParks and interested and concerned members of the community, last week.
The necessity to keep track of the spread of this beetle, originating from Asia, was highlighted during the presentation.
It had initially spread to California and Israel before it was noted in South Africa in the early 2010s.
Polyphagous – meaning ‘eats a variety of foods’ – is a very apt description of this beetle and although it seems to favour the English oaks and Plane trees, it has infected a variety of other exotic, as well as indigenous trees.
The beetle itself does not kill the tree, but the fungus, that it introduces as food for its larvae, inhibits the tree’s sap flow, and this eventually kills it. Some trees, even though attacked, have shown resistance to the beetle and/or the fungus.
Dr De Beer visited Belvidere and Knysna town and evidence of the beetle was found on the following trees: Exotic – English Oak (Quercus ruber), Plane Tree (Platanus x acerifolia), Butterfly tree (Phanera (Bauhinia) purpurea).
Indigenous – Keurboom (Virgilia divaricata), Essenhout (Ekebergia capensis,) Real Yellowwood (Podocarpus latifolia,) Outeniqua Yellowwood (Podocarpus falcatus), Common spike-thorn (Gymnosporia buxifolia), Sweet thorn (Vachellia (Acacia) karroo) are also targets for the beetle.
In Johannesburg, the once forested area of Sandton is losing trees at an alarming rate, and there is no way to stop the spread, as there is currently no effective way of controlling the beetle.