The potential economic impact of the polyphagous shot hole borer invasion in South Africa has been calculated to be a massive R275 billion over the next ten years, if nothing is done to stop the spread of this invasive beetle. Researchers from FABI collaborated with Stellenbosch University (SU) ecologists and economists to model the unmitigated economic impact of the PSHB invasion, with the findings recently published in the Journal of Economic Entomology.

In 2017, the polyphagous shot hole borer was detected in the KwaZulu-Natal National Botanical Garden, South Africa, however, there is evidence through DNA sequencing that the species has been in the country since at least 2012. It has since spread to eight of South Africa’s nine provinces, making it the largest current outbreak of this invasive pest globally.

A collaboration between economists and ecologists at the Stellenbosch University School for Public Leadership, the DSI-NRF Centre of Excellence for Invasion Biology, SU’s Department of Conservation Ecology and Entomology, and FABI researchers Trudy Paap and Wilhelm de Beer, used a modelling approach based on forecasted impacts. The paper, published in the Journal of Economic Entomology, modelled the potential cost of damage to trees in the agriculture and commercial forestry sectors, as well as native trees in natural forests, and urban trees. The predicted cost was a whopping R275 billion, with most of the costs being for the removal of urban trees that die as a result of the beetle and its fungal symbiont.

The authors state that if nothing is done to slow the spread of this pest, municipalities country-wide will have to remove and safely dispose of an estimated 65 million urban trees between 2020 and 2030. To date, there is no thoroughly tested and approved insecticide or fungicide registered in South Africa to treat infestations of the shot hole borer effectively. In light of the lack of proven registered treatments, the removal of heavily infested reproductive host trees is considered an important strategy to reduce the number of PSHB beetles in the environment. Restricting the free movement of potentially infested planting material, wood and wood products will be an important measure to reduce further spread.

Researchers at FABI, in collaboration with colleagues from several other Universities, are co-ordinating monitoring efforts and leading research on the PSHB and its fungus in South Africa. Background information on the PSHB and its management, information on its distribution and host trees in South Africa, and feedback on ongoing research and monitoring efforts by the PSHB Research Network can be found on the FABI PSHB website.

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