Rhodes University’s Centre for Biological Control (CBC) was joined by Water and Sanitation Deputy Minister, Sello Seitlholo at Hartbeespoort Dam to officially release the Salvinia weevil, a biological control agent known as Cyrtobagous salviniae, to manage the Salvinia invasive plant on the dam.

Professor Julie Coetzee and DWS deputy minister Sello Seitlholo at Hartbeespoort Dam on Monday.

Salvinia minima is an invasive floating alien aquatic weed, otherwise known as the common salvinia, currently plaguing the dam, along with the invasive hyacinth. It usually takes over when the hyacinth dies off.
The deputy minister, alongside Professor Julie Coetzee, Deputy Director of the CBC and Principal Scientist at the NRF South African Institute for Aquatic Biodiversity, released the first weevils in the Crocodile River just upstream of Hartbeespoort Dam.
The weevil species is a subaquatic herbivorous insect that feeds on the invasive aquatic plant, the common salvinia. The invasive alien plant from South America was first recorded at Hartbeespoort Dam in 2011 and has since spread through the North West and Gauteng. It has already reached the Limpopo River, the border with Botswana. This invasive plant threatens South Africa’s water bodies.
The weevil is an effective classical biological control agent used in several countries.
CBS is one of many research laboratories that dedicated several years to testing a biological control agent Cyrtobagous salviniae and was granted approval for release of the insect late in 2024. The CBC in collaboration with community partners, will rear the weevil and facilitate release at various sites across the country where water is invaded by common salvinia. This biological control programme and the progress of the weevil and its impact on common salvinia will be closely monitored.
The weevil is host-specific and will not target any other plants. As with the hyacinth bug, it dies when the plant dies.