Recent reports of the polyphagous shot hole borer outbreak and infestation, which eventually kills trees, has City Parks worried.
Residents in Hurlingham, Craighall Park, Dunkeld, Sandton, Parkview, Kensington and Houghton have reported diseased trees in their yards and on the street, and the likelihood of the infestation being more widespread was a possibility, the utility said.
The shot hole borer is a type of minute beetle that embeds its eggs deep in the inner layers of the tree, said MMC for Social Development, Nonhlanhla Sifumba.
“The larvae, once matured, then make their way out of the tree by tunnelling holes. The lesions on the trees may vary based on the tree species to resemble ‘pinheads’ or a series of ‘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 kills the tree and can destroy a cluster of adjacent trees once the young beetles start to nest.”
She added that City Parks was working closely with institutions such as the Forestry and Agricultural Biotechnology Institute to survey the extent of the spread of the infestation.
A chemical-controlled trial in Hurlingham was set to start, she said, and residents could report diseased trees at [email protected]
Residents are urged to look out for diseased symptoms which vary in different tree species, from patches of white powdered wood called frass to blotches of oozing resin or gumming along the holes in the tree.
“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 it in a controlled manner through burning.”
While the beetle has been devastating in other parts of the world, including Asia and California in the USA, Sifumba was cautious not to cause panic until the true extent of the infestation was determined.
“The pine species seems to display a natural repellant to the shot hole borer and we are therefore very fortunate that the paper manufacturing industry is not affected.”
Reports received indicate that indigenous trees native to southern Africa such as the vachellia (acacia) sieberiana, which is commonly referred to as the paperbark thorn, have also been affected.
Sifumba said City parks would work with all bodies and concerned groups to ensure that the infestation was tackled collectively to preserve and protect Joburg’s manmade forest.