In a bid to combat South Africa’s growing problem of invasive aquatic plants, scientists are turning to an unexpected ally—hungry weevils from Louisiana. These tiny insects have shown great potential in controlling invasive plant species, particularly water hyacinths, which have been wreaking havoc on South Africa’s waterways. Water hyacinths, native to the Amazon Basin, were introduced to South Africa over a century ago as ornamental plants. However, without natural predators to keep them in check, these fast-growing plants have spread uncontrollably, choking rivers, lakes, and dams.

The dense mats they form block sunlight, reduce oxygen levels in the water, and disrupt local ecosystems. They also pose a significant threat to agriculture, fishing industries, and water supply systems. Scientists believe that a specific species of weevil, Neochetina eichhorniae, native to Louisiana, could be the solution. These weevils feed exclusively on water hyacinths, damaging their leaves and stems, which weakens the plants and slows their growth. Previous biocontrol efforts using these weevils in other parts of the world have yielded promising results, leading researchers to consider introducing them on a larger scale in South Africa.

“Weevils have been successfully used in countries like the United States, Australia, and several African nations to control water hyacinth populations,” said Dr. Pieter van Wyk, a South African biologist specializing in aquatic plant management. “By introducing them here, we hope to see a significant reduction in the spread of these invasive plants, which are threatening our biodiversity and water resources.” The introduction of foreign species for biocontrol purposes is always approached with caution to ensure they do not become invasive themselves. Extensive studies have been conducted to confirm that Neochetina eichhorniae weevils pose no threat to native plant species.

South African authorities are closely monitoring the initiative to ensure ecological balance is maintained. Beyond their environmental benefits, the weevils also offer a cost-effective and sustainable alternative to chemical herbicides, which can harm native wildlife and contaminate water sources. Mechanical removal of water hyacinths is labor-intensive and provides only temporary relief, making biological control a more attractive long-term solution. If successful, this project could serve as a model for tackling other invasive plant species worldwide.