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Since then it has been detected in all provinces, and is a risk not only to indigenous and decorative trees but also to agricultural crops.

The beetle is two millimetres in size and has already been identified as the cause of massive tree deaths in the Johannesburg urban areas, George and in Knysna. The beetle (Euwallacea nr fornicatus) is an ambrosia beetle (of the weevil family) and is native to Southeast Asia. What makes it so destructive is the mutually beneficial relationship it has with three species of fungi, including the pathogen Fusarium euwallaceae.

The adult female beetles bore through the bark into the sapwood and inoculate the fungus, which grows in the tunnels the beetles have created. The fungus then serves as food for the beetle.

Trees that are more susceptible to the beetle can develop the disease Fusarium dieback, which disrupts the flow of water and nutrients within the tree and can eventually lead to death.

Paap, of the University of Pretoria’s forestry and agricultural biotechnology institute, said that if the borer was picked up early enough, it was possible it could be eradicated. However, she said “it has become evident that the beetle has been prevalent in South Africa for five or six years prior to detection”.

The Department of Agriculture, Forestry and Fisheries (DAFF) said it had also had reports of infestations on pecan trees in Hartswater, Northern Cape province. “The department has since established a working committee with other relevant stakeholders to do more research on the pest and how it can be effectively controlled.”

The department also identified important crop tree species that can be infected such as avocado, macadamia, peach, orange, grapevine pecan trees and forest trees such as the cabbage tree, monkey plum, common coral tree and honey flower.

The department said the movement of infested wood is the main way the beetle is spread.

It said the appropriate disposal of infested trees (by chipping/composting, solarisation or burning) will be key to reducing the spread of this damaging pest.

“Surveys to monitor the spread of the beetle and fungus throughout South Africa are continuing, and chemical treatment trials and experimental trappings are planned. The public can assist by looking out for symptoms and reporting symptoms to the relevant authorities,” said the department.


Source: News24