by Nosipho Mngoma
Durban - Brazilian bugs have been released to control alien invasive plants which threaten a proposed World Heritage site near oThongathi (Tongaat).
Rhodes University’s Dr Iain Paterson released 200 Pereskia stem-wilter insects (Catorhintha schaffneri) at the Sibudu Caves site in the Qwabe area on Wednesday.
This was done to control the growth of Pereskia (Pereskia aculeata), which destroys indigenous plants.
Paterson, an entomologist working in biological control, flew to Durban from Grahamstown to release the bugs after receiving a call for help from Noreen Ramsden, the secretary of the Friends of Sibudu, a non-profit organisation assisting in the preservation and promotion of the site and its surrounds.
“We had to come here because this site is so important and special because of the archaeological dig. Controlling Pereskia this way is environmentally friendly, it’s safe and sustainable,” said Paterson.
Sibudu is one of the South Africa’s most important archaeological sites. Since excavation started in 1998, artefacts dating back 77 000 years have been recovered and studied as well as displayed around the world, including at the Smithsonian Museum in the US.
Barbara Dunn, secretary of the KZN branch of the South African Archaeological Society and a member of the Sibudu Trust, had worked on the site as an undergraduate archaeology student some years ago.
She said controlling the invasive plant was always on their list of things to do to preserve the site, which the trust was looking to buy to develop as a cultural, tourism and educational resource.
Pereskia grows uncontrollably at the site.
Paterson, whose work at Rhodes is aimed at developing new strategies for the control of alien invasive plants, has been researching the stem-wilter since 2007. It was only released to control Pereskia for the first time in 2014, including in eManzimtoti.
Pereskia was introduced to South Africa in the 1850s from Brazil, where it is an important part of their heritage and biodiversity said Paterson.
There, up to 16 types of insects feed on it, controlling its growth. With no natural enemies in South Africa, it grows uncontrollably, covering and weighing down indigenous plants causing them to collapse and die.
In terms of the Alien and Invasive Species Regulations of the National Environmental Management: Biodiversity Act, Pereskia is a category 1B species, meaning it is prohibited to import, grow, move, sell or buy the plant.
According to Karen Hope, the KZN biodiversity officer for the national Department of Environmental Affairs, clearing the plant by hand has proved difficult.
Workers cut the plant and treat it with herbicide. It is then left to dry for about two weeks before it is burned.
However, it has been found to grow again where it was burned.
Working for Water, a project of the department, contracts the South African Sugarcane Research Institute to grow the stem-wilter.
Although priority is usually given to eradicating alien invasive plants in water catchment areas, the release at Sibudu was important not only because of the archaeological significance but because of its inaccessibility.
“There is a health and safety concern for sending in teams here to manually remove the plant,” she said. Much of the Pereskia covers the cliff face and its stem has prickly spines.
Paterson will return to the site in September to check on the progress of the insects which he hopes would have established themselves to eat away at the pesky plant.