The City of Cape Town has developed best practice methods for the removal and disposal of trees infested with the invasive Polyphagous Shot Hole Borer beetle (PSHB).

Horticulturists, landscapers, arborists or contractors assisting residents with the removal of dying, or dead trees are requested to follow this protocol.

In March 2019, a possible PSHB beetle infestation was discovered in Oldenland Road, Somerset West, in an ailing London plane tree. In April 2019, DNA tests conducted by scientists confirmed it was a positive PSHB identification.

An experienced invasive species removal team from the City has since then removed 46 trees from the Somerset West area in an attempt to contain and limit the spread of this invasive Asian borer beetle. The wood, from trees cut down in Somerset West, was chipped on site and carefully removed under cover of heavy-duty plastic and incinerated at appropriate sites.

Best practice

The City of Cape Town’s Invasive Species Unit, in cooperation with the City’s Recreation and Parks Department, local arborists and the country’s top entomologists, released a PSHB Protocol which prescribes the best practice for how to remove and dispose of trees infested with PSHB.

The 18-page Polyphagous Shot Hole Borer Protocol is useful for identifying, pruning, cutting down, removing and disposing of infected PSHB wood.

Experiences in California, Israel, and closer to home – in Gauteng, have shown that the PSHB beetle can easily spread across suburbs if extra precaution is not taken. Apart from infected wood, the 2mm borer beetle can also spread through clothing, vehicle crevices, or unclean horticultural equipment.

The authors of the protocol advise that the use of pesticides and fungicides have a limited effect. These may reduce the rate of recolonisation in lightly infected trees but have not proven effective at eradicating PSHB from infected trees.

The movement of infested wood is an important pathway for the spread of the beetle. Appropriate disposal of infested trees – by chipping and then incineration, solarisation, or composting – is therefore essential for reducing the spread of the pest.

The PSHB Protocol is available to anyone who needs a scientific and realistic set of best practice advice for dealing with a PSHB infestation.