Borer beetle threat: public asked to help
The George Municipality is considering urgent measures to save local trees from a new borer beetle infestation and is appealing to citizens to help report signs of infection.
George Municipality Director of Community Services, Walter Hendricks, said reports of the Polyphagous Shot Hole Borer (PSHB) or Euwallacea fornicatus and its associated fungus killing trees in other parts of the country sparked an investigation into a possible local infestation. "Our fears were confirmed and advanced infection was detected in several large trees in Doneraile Square, Van Riebeeck Garden and Camphersdrift. This was just a cursory investigation to confirm the threat, but we expect to discover more. George is a tree-rich city and we are concerned for our residential trees as well as surrounding farms and forestry," said Hendricks.
The PSHB beetle is relatively new to South Africa and a possible viable commercial chemical fungicide is currently only available wholesale. The George Municipality and other local role players are meeting with University of Pretoria Professor Wilhelm de Beer of the Ambrosia Beetle Working Group next week to discuss control strategies. "The municipality will also be consulting with other local authorities to investigate all options," said
The PSHB and its fungus were first discovered in South Africa during a routine survey for tree pests at the KwaZuluNatal Botanical Garden last year. It is a 2mm-long ambrosia beetle native to Southeast Asia and carries several fungal species with it. It bores through the bark into the sapwood of trees and inoculates the fungus into living wood. The fungus grows in the beetle tunnels and serves as food for its larvae. In susceptible trees, the fungus can spread through the sapwood, causing disease and even death.
All trees vulnerable
The situation is worsened by the fact that the beetle and fungus is not host specific, but seem to be affecting a wide range of indigenous and exotic trees, including Chinese and Japanese maple, plane trees, kapok trees, paperbark acacia, wild
plum, dwarf coral and common coral. Surveys have also indicated susceptibility of important crop trees such as avocado, macadamia, pecan, peach, orange and grapevine.
So far symptoms most seen on trees in George are small elevated blue-black lesions on the bark resembling shotgun wounds or cigarette burns. Other symptoms include patches of white powdered wood on the bark surrounding entrance holes of beetle tunnels and blotches of oozing resin on the bark. The municipality appeals to the public to inspect the trees on their properties as well as in parks and sidewalks and to report back to parks@ george.gov.za
One of the first residents in George to spot the beetle infestation was Johanna Vermeulen, who reported it to the George Municipality. Several trees in her garden have died and a favourite shade tree got the axe, but this has not halted their activities in her garden. Priscilla Burgoyne, Garden Route Botanical Garden herbarium curator, said several keurboom trees show all the symptoms of beetle infestation, a cause for great concern as it would be tragic if the garden loses all its beautiful trees to the infestation.
Residents in Wright Street in Camphersdrift may not have noticed, but the PSHB beetle has been hard at work. The George Municipality hopes to save the town’s trees with immediate interventions.
The resin running down the bark of this keurboom tree in the Garden Route Botanical Garden is a tell-tale sign of penetration by beetles. Infestation of trees by the PSHB beetle was also found in Doneraile Square, where trees are dying.
This stump is all that remains of a giant ash tree that used to provide shade in Johanna Vermeulen’s Camphersdrift garden. After infestation was discovered it was felled and treated with chemicals, but new spots keep appearing.