Ricochet News

Public appeal to report new borer beetle threat to trees

Apr 4, 2018
Public appeal to report new borer beetle threat to trees

The George Municipality is considering urgent measures to try save local trees from a new borer beetle infestation and is appealing to citizens to help report signs of infection.

George Municipality Director Community Services, Walter Hendricks, said that 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 possible local infestation.

“Our fears were confirmed and advanced infection was detected in several large trees in Donneraile Square, Van Riebeeck Gardens 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 possible control strategies.

“The municipality will also be consulting with other local authorities to investigate all options in dealing with this disease as effectively as possible,” said Hendricks.

The PSHB and its fungus was first discovered in South Africa during a routine survey for tree pests at the KwaZulu-Natal Botanical Gardens 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’s tunnels and serves as food for its larvae. In susceptible trees the fungus can spread through the sapwood causing disease and even death.

The situation is worsened by the fact that the beetle and fungus is not host specific but seems to be affecting a wide range of indigenous and exotic trees, including Chinese and Japanese maple, plane trees, Kapok trees, paper bark acacia, wild plum, dwarf corral and common corral.

Overseas surveys have also indicated susceptibility of important crop trees such as avocado, macadamia, pecan, peach, orange and grapevine.

Symptoms most seen on trees in George so far 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 in parks and sidewalks and to report the occurrence of symptoms to parks@george.gov.za Please include the physical position or address where the trees are standing as well as the symptoms. Photographs of the extent of the infections are welcome.

Images: Samples of infestation of trees by the PSHB beetle in Donneraile Square. These trees showed signs of dying off. Picture credit (optional): George Municipality

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