Deputy Minister Seitlholo introduces biological control agents to target specific aquatic plant, Salvinia Minima at Hartbeesport Dam
Deputy Minister, Sello Seitlholo, and Rhodes University’s Centre for Biological Control (CBC) have officially released the Salvinia weevil insect, a biological control agent known as Cyrtobagous salviniae, to manage the Salvinia minima, an invasive floating alien aquatic weed, otherwise known as the common salvinia, at the Hartbeespoort Dam.
The Deputy Minister was joined by Professor Julie Coetzee, Deputy Director of the Centre for Biological Control and a Principal Scientist at the National Research Foundation’s South African Institute for Aquatic Biodiversity.
The weevil species is a subaquatic herbivorous insect that feeds on the invasive aquatic plant, the common salvinia. The species were imported from Florida State in the United Sates of America (USA) and it has proven to be effective and successful to control the aquatic plant in the USA.
The invasive alien plant said to be from South America was first recorded at Hartbeespoort Dam in 2011, and has since spread through areas of the North West and Gauteng provinces, and has reached the Limpopo River, which marks the border with our neighbouring country of Botswana, threatening South Africa’s water bodies.
According to Prof Coetzee, the weevils multiply quickly and their impact of controlling the aquatic plant can be observed in a year. She says 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.
Prof Coetzee also indicated that the weevils only feed on the salvinia minima plant and their entire life cycle depends on the plant, thus they do not have a threat to infest other ornamental plants, crops or even the water hyacinth plants.
Deputy Minister Seitlholo welcomed the bugs and said the introduction of the insects is was attempt by the Department of Water and Sanitation to deal with a widespread problem of alien invasive species along the Crocodile River and at the Hartbeespoort Dam.
“It is important for us as the Department to secure our water resources by partnering with scientific institutes like the Centre for Biological Control. What is also important is for us to get into serious conversations with municipalities on the upper catchment that are largely responsible for causing high nutrient load in the water due to their substandard effluent discharged from their waste water treatment works that is being released in the river, eventually landing in the dam. This results in high nutrient levels in the water which gives rise to the spread of these alien invasive aquatic plants, compromising the ecosystem, recreation and the general local economy,” said Deputy Minister Seitlholo.
Deputy Minister Seitlholo said the use of biological control agents, weevils, will run concurrently with other remediation programme currently underway at the dam and implemented by Magalies Water to eradicate alien invasion species that have negatively impacted the ecosystem in the water. The remedial programme includes the physical removal of the water hyacinth at the dam and the pilot project of nanobubbles technology which increases dissolved oxygen in the water, activating the decomposition of microorganisms in water or river sediment.
Since the quality of water is affected by the discharge of effluent and raw sewage from municipalities of Tshwane, Johannesburg and Ekurhuleni, Deputy Minister has lamented the fact that those municipalities do not play a role in the remediation programmes undertaken by the Department to rehabilitate the water resource.
To address the problem of water pollution by municipalities, Deputy Minister said despite the proactive ways of engaging the municipalities through the Department’s Compliance, Enforcement and Monitoring Directorate, the Department has also proposed amendments to Section 19 of the National Water Act (NWA) which focuses on preventing and remedying the effects of pollution, and also ensuring the protection of water resources and addressing pollution incidents
Deputy Minister Seitlholo also emphasised that the proposed amendments to NWA, which are currently with the State Law Advisor, enable the department to directly hold the Executive Mayor and the Municipal Manager liable for the transgression of the municipality in terms of the pollution of the country’s water courses. He stressed that these legislation measures are taken by the Department to fundamentally deal with issues of water pollution in the country.
Media enquiries:
Wisane Mavasa, Spokesperson for the Department of Water and Sanitation
Cell: 060 561 8935
E-mail mavasaw@dws.gov.za
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