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March 2nd, 2018 / The Conversation

Sandton is Johannesburg’s economic hub – home to numerous companies’ headquarters and the Johannesburg Stock Exchange. And now it has a new, unwelcome resident: a tiny beetle that could lay waste to several tree species found in the suburb and potentially the wider Johannesburg area. This is particularly concerning, as Johannesburg is considered one of the world’s largest urban forests, with more than 10 million trees.

The polyphagous shothole borer, or Euwallacea fornicatus, seems to be a newcomer to South Africa. It was discovered in the country for the first time in 2017 by Dr Trudy Paap, a postdoctoral fellow at a biotechnology institute at the University of Pretoria.

During a survey for diseases in the KwaZulu-Natal Botanical Gardens in Pietermaritzburg, Paap found a lane of infested plane trees. The identity of the beetle was subsequently confirmed and the tiny beetle – they are each about 2mm long – has been found at work in gardens and roadsides in Johannesburg, about 500 km from Pietermaritzburg.

The beetle isn’t alone. It carries several fungal species with it when it infests living trees. One of these, Fusarium euwallacea, seems to be a permanent associate of the beetle. This fungus can eventually kill a beetle-infested tree.

The beetle and the fungus have devastated trees in California in the US as well as in Israel. Insecticides aren’t effective because the beetles bore deep into the wood. Read more