Hartbeespoort: Water and Sanitation Deputy Minister, Sello Seitlholo, and the Rhodes University Centre for Biological Control (CBC) have released weevil species to tackle the invasive alien aquatic plant at Hartbeespoort Dam in the North West. The salvinia weevil insect is a biological control agent known as Cyrtobagous salviniae, used to manage the Salvinia minima, an invasive floating alien aquatic weed (known as the common salvinia).
According to South African Government News Agency, the weevil species is a subaquatic herbivorous insect that feeds on the common salvinia. The species were imported from Florida State in the United States of America (USA), and it has proven to be effective and successful in controlling the aquatic plant in the USA. Joined by Professor Julie Coetzee, the Deputy Director of the Centre for Biological Control and Principal Scientist at the National Research Foundation’s South African Institute for Aquatic Biodiversity, Seitlholo officially released the salvinia weevil insect on Monday at Mogi Adventures, located next to the Crocodile River.
The invasive alien plant was initially recorded at Hartbeespoort Dam in 2011, and has since spread through areas of the North West and Gauteng Provinces, reaching the Limpopo River, which marks the border with the neighbouring country of Botswana, threatening South Africa’s water bodies.
According to Coetzee, the weevils multiply quickly and their impact on controlling the aquatic plant can be observed in a year. She stated that the CBC, in collaboration with community partners, will rear the weevil and facilitate releases at various sites across the country where water is invaded by the common salvinia. ‘This biological control programme will be monitored and the progress of the weevil and its impact on common salvinia will be noted,’ Coetzee said, adding that the weevils only feed on the salvinia minima plant, thus posing no threat to other plants or crops.
Seitlholo emphasised the importance of securing the country’s water resources by partnering with scientific institutes like the CBC. He highlighted the critical need to engage with municipalities in the upper catchment areas responsible for the high nutrient load in the water due to substandard effluent discharged from wastewater treatment works. This discharge results in high nutrient levels, promoting the spread of alien invasive aquatic plants and compromising the ecosystem, recreation, and local economy.
He also mentioned that the use of the weevils will run concurrently with other remediation programmes at the dam, implemented by Magalies Water, which includes the physical removal of water hyacinth and a pilot project of nanobubbles technology to improve water quality.
Seitlholo further noted that municipalities ought to play a role in the remediation programmes undertaken by the department to rehabilitate the water resource, given the quality of water is affected by effluent and sewage discharge from the municipalities of Tshwane, Johannesburg, and Ekurhuleni.
Despite engagements by the department’s Compliance, Enforcement and Monitoring Directorate with municipalities, Seitlholo stated that proposed amendments to Section 19 of the National Water Act (NWA) are currently with the State Law Advisor. These amendments aim to hold the executive mayor and municipal manager accountable for municipal transgressions related to water pollution.
‘These legislative measures are taken by the department to fundamentally deal with issues of water pollution in the country,’ Seitlholo said.