In March this year, Jaqui van Dyk, a Junior Researcher at the CBC, travelled to the United States to collect the Florida biotype of Cyrtobagous salviniae—a small but highly specialised weevil that feeds specifically on Salvinia minima. This fast-spreading aquatic weed is emerging as a significant problem in South Africa, and the need for a targeted biological control agent has become increasingly urgent.
Although closely related to the Brazilian biotype commonly used to control Salvinia molesta, the Florida biotype is smaller and feeds on S. minima. With infestations increasing across South African rivers and dams, this weevil offers a promising solution.
During her trip to the United States, Jaqui met with Rodrigo Diaz and his team at Louisiana State University’s Biocontrol Lab, where she received practical, hands-on training in the rearing and maintenance of the C.salvinae culture. She worked closely with Dane Shackleton, who leads LSU’s mass-rearing programme for Salvinia weevils, gaining valuable experience in the day-to-day care, culturing, and release strategies used in their system.
Jaqui also met with researchers and students working across various invasive plant projects in the region. These exchanges created opportunities for shared learning, with Jaqui presenting on South Africa’s successful use of Megamelus scutellaris to control water hyacinth (Pontederia crassipes). Her insights generated considerable interest, as teams in the US begin exploring similar release methods based on CBC’s proven successes.
In addition to lab work, she was taken on field tours through Louisiana’s iconic wetland and swamp systems. These excursions showcased the range of aquatic invasives being tackled in the region, including water lettuce (Pistia stratiotes), water hyacinth, Salvinia minima, and the invasive Apple Snail. Seeing the scale of these infestations and the local responses was eye-opening and reaffirmed the importance of proactive biocontrol efforts.
The return to South Africa marked the next milestone: the official release of the weevils into a dam at Mogie’s Adventure in Hartbeespoort on the 17th of March 2025. This was hosted jointly by the CBC and the South African Institute for Aquatic Biodiversity (SAIAB), and attended by the Deputy Minister of Water and Sanitation, Mr Isaac Sello Seitlholo.
The Deputy Minister personally released the weevils into the dam, marking a major symbolic and practical step forward in the fight against S. minima. The event received strong media coverage and highlighted the importance of biological control as an environmentally friendly, sustainable solution to South Africa’s invasive aquatic weed problems.
A recent visit to the dam has shown promising results of visible feeding damage on the Salvinia minima plants, suggesting the weevils have not only survived but have begun establishing themselves. An encouraging early sign of success.
With the demand for C.salviniae rising rapidly across South Africa, the CBC is now preparing to import a larger shipment from LSU. As part of this collaboration, an LSU student will be travelling to South Africa to accompany the next consignment of weevils and spend time working alongside the CBC team.
During her visit, the CBC will share their experience and expertise in rearing Megamelus scutellaris, a practice that has seen considerable success locally and is now gaining interest globally. This knowledge exchange forms part of a growing international partnership that benefits both countries and strengthens global capacity to address invasive species.
The collaboration between researchers in South Africa and the United States demonstrates the power of shared knowledge and collaboration. The hope is that C.salviniae will establish across Salvinia-infested sites, helping to restore ecological balance and preserve aquatic biodiversity in South Africa.
