The Dangers Of Polyphagous - Shot Hole Borer

Although these pests may be tiny, the presence of Polyphagous Shot Hole Borer (PSHB) in South Africa is a massive cause for concern.

- Madison Moulton

Geographically, this is the largest outbreak of PSHB in the world, affecting over 80 tree species in agricultural, commercial and urban sectors. The first local discovery was made in the KwaZulu-Natal National Botanical Gardens, and the beetle’s presence has since been confirmed in eight of our nine provinces. Unfortunately, there is currently no effective treatment available, and once the beetle has made its way into a tree its demise seems inevitable.

The deadly spread

PSHB is native to Southeast Asia, but due to globalization and increased interconnectedness the beetle has through international trade found its way to Israel, California and now South Africa. As they are so tiny (about 2mm long) and burrow into the wood, they are very difficult to detect in early stages and are often only discovered as the host tree shows signs of dying. The problem has spread throughout the country with the movement of infested deadwood (like firewood). Current projections of the scale of the infestation reach up to half a million trees in Gauteng alone, and that number is set to grow. Without proper management and awareness, the potential for the continued spread of PSHB through wood products is a huge risk. A forecast by the website Tree Survey predicts that by 2022 all urban sites across the country will have a presence of PSHB, and the areas with current high levels of infestation will reach the maximum level of infestation of susceptible trees (20 – 30% of all trees).

The Science-y Stuff

The beetle itself (