Beetle infestation puts Joburg's tree canopy at risk

Johannesburg City Parks and Zoo is investigating an outbreak and infestation of borer that is killing trees in several suburbs.

Residents in Hurlingham‚ Craighall Park‚ Dunkeld‚ Sandton‚ Parkview‚ Kensington and Houghton have reported diseased trees in their yards and on the street‚ mayoral committee member for community development Nonhlanhla Sifumba said on Wednesday.

“Polyphagous Shothole Borer … is a minute beetle that embeds its eggs deep in the inner layers of the tree. The larvae‚ once matured‚ then make their way out of the tree by tunnelling holes‚” a statement by the MMC read.

“The holes resemble ‘gunshots’ that stifle the flow of nutrients through the veins of a tree‚ resulting in a tree that is visibly diseased from the top. This is eventually fatal for the tree and can destroy a cluster of adjacent trees once the young beetles start to nest.”

The city’s parks and zoo department is working closely with institutions such as the Forestry and Agricultural Biotechnology Institute (FABI) to survey the extent of the spread of the infestation.

Sifumba appealed to residents to report diseased trees to trees@jhbcityparks.com.

“We are in the process of identifying the extent of the infestation of the Shothole Borer to the tree canopy of the City of Joburg‚ and the environment as a whole in order to mitigate the far reaching implications” said Sifumba.

The beetle has been devastating in other parts of the world but Sifumba was cautious not to cause panic until the true extent of the infestation was ascertained.

“Pesticides are not effective as well‚ because the beetle bores deep into the wood. The only known method of managing the spread is to cut down infested trees hosting the beetle‚ and to dispose of them in a controlled manner‚ through burning‚” Sifumba explained.

Symptoms vary in different tree species - from patches of white powdered wood called frass to blotches of oozing resin or gumming. This weakens the trees’ immune system causing stress and die-back on the bark surrounding the hole.

While the city evaluates the extent of the infestation‚ it is also training personnel to identify the borer and other fungal hosts that accompany the beetle‚ disposing of trees in a designated area for controlled dumping and burning and ensuring that a tree replacement strategy is in place.