Western Cape agricultural experts say they are concerned about the spread of the polyphagous shot hole borer (PSHB), a small beetle that has invaded a Somerset West fruit farm, triggering alarm over its possible impact on the lucrative export industry.
The national Department of Agriculture, Land Reform and Rural Development say the tiny invasive pest – the beetles are each about the size of a sesame seed – has been found on agricultural crops in other provinces too, including KwaZulu-Natal and the Northern Cape.
In the Western Cape, the beetles were first spotted in Somerset West in 2019, and are estimated to have infested 10 000 trees in the Helderberg region to date.
The beetle is known to target a wide variety of trees; those affected usually die five years after first being infested.
Hortgro Science, a research body for the South African deciduous fruit farming industry, said a farm producing pears, plums and apples in Somerset West had recorded an infestation. There have yet to be reports of infestations on other farms in the province.
General manager for Hortgro Science, Professor Wiehann Steyn, said the infested area in Helderberg is small compared to the total area under deciduous fruit production in the province, but it might be more severe in the near future.
“The medium-term impact for the individual farm with infested orchards might be severe. PSHB may spread to major production areas in the Western Cape, with the obvious risk of a much more significant impact,” he said.
The Helderberg area contributed R416 million in pears and R105m in plums towards the City of Cape Town’s agricultural export values last year.
The Western Cape Department of Agriculture said it was aware of the effects a wide spread infestation might have on the sector.
“In that case, this could affect the production investment in the products. The Western Cape horticulture export basket may decline, and job losses will be prevalent in these fruit industries.
“To a greater extent, this would reduce the province's share of avocado, pears and plum exports to the national total,'' said head of economic agricultural services, Bongiswa Matoti.
According to Hortgro, pears account for more than 12 300 jobs and plums more than 7 000 jobs in the province.
The provincial Department of Local Government, Environmental Affairs and Development Planning said infestations have been confirmed in Plettenberg Bay, George, Knysna and Stellenbosch, but not on farms.
National Department of Agriculture spokesperson Reggie Ngcobo maintained that the impact of the highly-invasive pest on agricultural crops was minimal.
“Most of the agricultural crops that were infested have recovered. These include pecans, macadamia and avocados, especially in KZN, Northern Cape and Western Cape provinces,” he said.
Ngcobo said the disposal of infested material was a challenge in most municipalities.
CapeNature said it was protecting its reserves by preventing wood being brought into its protected areas.
“We are monitoring for the presence of the beetle when and where we can, but this is a specialised task and not easily done as it is even challenging for the experts to detect this beetle in the wild,” it said.
A study by Stellenbosch University found that the potential economic impact of the removal of the trees infested with the pests in the country could amounts to R275 billion over the next ten years, but there is no tested and approved insecticide in South Africa to treat the infestations.
Scientists indicated that 30% of urban trees are likely to be infested by the pests, which spend 98% of their life cycle inside the trees, making it difficult to manage them.
An ecologist from the Centre for Invasion Biology at Stellenbosch University, Professor Brian Wilgen, said there is no evidence that a reduction in the number of trees will have any effect on atmospheric oxygen.
“In urban areas, street trees are useful because they are aesthetically attractive, shady and have therapeutic advantages. In rural settings, they produce timber, nuts and fruit. These attributes are at risk,” he said.
The full extent of the distribution of the PSHB in the province is unknown at this stage.