Over 400 weevils have been released in the Vaal River on Thursday 15 February in an effort to halt the growth of water lettuce (Pistia Stratiotes) that has fast become a crises on the Vaal River.

Water lettuce is a poisonous and highly invasive free-floating freshwater weed that is found in water bodies and slow-moving waterways in warm regions. It was first seen in SA in the Suikerbosrivier in 2021.

According to prof Julie Coetzee from the Rhodes Centre for Biological Control, floating invasive species can effectively be controlled by these insects. The damage these insects do to the plants leads to the demise of the plants.
Although water lettuce and water hyacinths are different species, both produce thousands of seeds that remain viable for years in the sediment, she said.

During the release of the weevils and hoppers, dr. Leslie Hoy, Manager of Environmental Services at Rand Water, shared the integrated approach in managing water lettuce and hyacinth on the Vaal. This include physical removal, biocontrol, and chemical application.

Spraying of the herbicide Glyphosate on the Vaal was done for the first time last week by professional crop sprayers and drone operators.

Rand Water earlier stated that the application of all herbicides used on the project has been approved by both the Department of Forestry, Fisheries and the Environment, and the Department of Water and Sanitation South Africa “and they are set at a sub-lethal dose because we are implementing an integrated approach”.

According to Rand Water the sub-lethal dose increases the sugar and carbohydrate contents of the Pontederia crassipes plant making it more palatable for the biocontrol agent.

“The specific formulations of the glyphosate that were recommended are made based on expert opinion and research, and field work is being monitored for compliance, “Rand Water said.

The spraying of Glyphosate however has since caused wide spread reaction.
Yet, little is said on how government and municipalities are addressing the root of the water lettuce crisis – the constant sewage spill in the Vaal.

Prof. Anthony Turton’s earlier warning that no eutrophic system in SA has ever been effectively rehabilitated should not go unnoticed. He explained that a eutrophic system has high levels of nutrients, typically phosphate and nitrate, usually associated with sewage return flows.

“We are polluting our drinking water systems with untreated sewage, and this simple fact has major economic and social consequenses over time,” Turton said.

He added that the cost of making this water safe for human consumption will be passed onto the consumer. The logical solution is to stop polluting our rivers with untreated sewage.

The Emfuleni Local Municipality (Evaton, Sebokeng, Vaal Oewer, Vanderbijlpark and Vereeniging) is among the municipalities that had been warned in the past to stop dumping sewage into the river. Over the weekend a concerned citizen was quoted on Vaal River Rats SA’s Facebook page, saying that the sewage works south of Soweto had been pumping raw sewerage for years into the Klip River which flows into the Vaal at Vereening.

For the past weeks community members and organisations have been using their own resources and time to manually remove the water lettuce that government should be doing.

The department of water and sanitation as custodian of the national water resources has a responsibility to ensure that water resources are protected. With the alarming condition of numerous municipal sewage plants, stricter action against those responsible for pollution has long been long pleaded for.

The excessive growth of invasive plants such at water lettuce and hyacinth in the Vaal River can lead to a series of ecological problems including the suffocation of other aquatic plants, and can negatively affect the viability of other aquatic animals. It can also clog water pumps on the river bank and cause damage to farmers’ equipment.

On Sunday Vaal River Rats SA reported a big water lettuce carpet starting to build up at the Barrage wall with patches of hyacinth starting to build up in between. Urgent assistance from Rand Water was asked to clean in front of the Barrage.

But as long as the root of the problem is not addressed we are fighting a losing battle against the stranglehold of invasive plants on the Vaal.

“This is a crisis for the whole country. They do not understand the calamity that is coming their way. Water is life and without that, the country is gone,” Andrew Surtees of the Vaal River Rats SA said.