PSHB beetle poses a serious threat, says experts

The polyphagous shot hole borer. Picture: Forestry and Agriculture Biotechnology Institute, University of Pretoria

The City of Cape Town’s Recreation and Parks Department, and the Invasive Species Unit, have put operational plans in place to deal with an invasive beetle that poses a serious threat to trees in the metropole and surrounding areas

The polyphagous shot hole borer (PSHB) has invaded and damaged thousands of trees in other parts of the country and scientists and horticultural experts are concerned that trees in Cape Town could be infected.

“We should not underestimate the damage that the beetle could cause to trees. Invasive species of this nature could go undetected as people don’t usually inspect trees to see if there are any beetles on the tree,” said mayoral committee member for community services and health, Zahid Badroodien.

The beetle is known to invade the host tree and bore holes in the branches. If undetected, it can destroy a tree within a relatively short period of time.

Adult beetles invade a variety of tree species and dig tunnels
to lay eggs. The PSHB beetles
then transport a fungus which attacks the tree’s vascular tissue, causing a disease called fusarium dieback (FD). FD in turn interrupts the supply of water and nutrients to the tree.

It’s known that PSHB attacks more than 300 tree species countrywide of which more than 130 of these species are susceptible to FD.

The PSHB beetle attacks a variety of tree species which include oak, most willows, plane trees, avocado, some acacias and most maples. These species include some of the most common and valuable trees in Cape Town. Tree species’ response to the pest varies and, if detected soon enough and provided that the infection is in an early stage and on a minor branch, it can be effectively treated.

“The City is working closely with the Forestry and Agricultural Biotechnology Institute (FABI) of the University of Pretoria to ensure that the latest technology is shared; and to update databases for current and future research, in an effort to more effectively control the PSHB,” said Mr Badroodien.

As adult beetles only grow up to 2mm in length they can be difficult to identify, but their presence can be confirmed by a tree’s symptoms, the most common of which are gum extraction on the bark; entry and exit holes, sugary secretions and staining.

The City’s Invasive Species Unit, and the Recreation and Parks Department, are calling on residents to report any sightings of the beetle by sending an email to Invasive.Species@capetown.gov.za or phoning the City’s toll-free number on 0860 103 089.

For information on invasive species you can visit www.invasivescapetown.org.za