Planthoppers are winning the war against water hyacinth — and in South Africa, this invasive aquatic weed has become a serious threat to dams, rivers, and the ecosystems and communities that rely on them. Originally from the Amazon Basin, water hyacinth spreads rapidly in nutrient-rich water, forming dense mats that can completely cover the surface. That blanket blocks sunlight, reduces oxygen levels, and disrupts aquatic life.
What makes water hyacinth especially difficult to manage is its persistence: its seeds can remain viable in the soil for more than 20 years. We’ve seen the damage this can cause in high-profile areas like Hartbeespoort Dam and the Vaal River — and other water bodies have faced ongoing pressure too, including Benoni’s Middle Lake and Civic Lake.
The good news? A surprisingly effective biological solution is making a measurable difference — and it comes in the form of tiny insects doing big work.
What is a planthopper?
Adult planthoppers (scientific name: Megamelus scutellaris) are small sap-sucking insects — roughly 3mm long — ranging in colour from pale cream to dark brown. But their size is misleading.
These planthoppers feed by piercing the plant tissue and drawing sap from the hyacinth. In the process, they damage the cells and weaken the plant structure. Over time, the water hyacinth begins to rot and sink — and once that breakdown starts, regrowth becomes far less likely. It’s a biological “pressure system” that steadily reduces the weed’s dominance without the same environmental trade-offs that can come with heavy chemical intervention.
Even better: planthoppers can be mass-reared. That means they can be grown in large quantities at dedicated rearing stations and released repeatedly where infestations are severe — increasing long-term impact.
The role of planthopper rearing facilities
To make biological control successful, you need more than the insect itself — you need the infrastructure to produce and sustain it at scale.
CSG Landscaping is proud to support the construction of specialised planthopper rearing facilities designed to replicate the warm, humid conditions of the Amazon environment where these insects originate. These stations function similarly to greenhouses: half-circle tunnel structures with metal frames, covered in protective plastic, and supported by specialised breeding boxes and controlled conditions.
Because the lifecycle is relatively short — development from egg to adult takes around three weeks — well-managed rearing facilities can increase planthopper populations quickly and consistently, which is critical for sustained release programmes.
Real-world results: Benoni and Hartbeespoort Dam
With the rearing infrastructure in place, planthopper releases on Middle Lake began in November 2023. Despite being considered late in the season, early 2024 monitoring showed the population steadily increasing, reaching 3,525 planthoppers per m² — a promising early indicator that biological control was successfully establishing.
A similar approach has been used at Hartbeespoort Dam, where intensive and repeated releases from early spring through summer 2023/2024 reduced water hyacinth cover from roughly 35% in peak summer to 5% by March 2024. At that point, planthopper densities were estimated at around 10,000 per m².
Since the establishment of rearing stations and repeated releases began in 2019 at Hartbeespoort Dam, coverage has reportedly been reduced to below 5% every year — showing what’s possible when biological control is sustained, monitored, and supported properly.
Long-term, collaborative, and effective
Projects like these work because they are long-term by design — and because they are built on collaboration between specialists. Our contribution to constructing rearing tunnels and support infrastructure, alongside partners such as the Centre for Biological Control and Rhodes University, strengthens the likelihood of ongoing success in reducing water hyacinth coverage over time.
When an invasive weed can regenerate and spread so aggressively, managing it isn’t a one-off job — it requires a consistent strategy, the right facilities, and teams who understand the environment, the operational realities, and the details that make projects like this sustainable.
Raising a child takes a village — and so does rearing hundreds of thousands of planthoppers. In many ways, that’s exactly why planthoppers are winning the war against water hyacinth: the science, the infrastructure, and the people all have to work together.
CSG Landscaping is proud to be part of that village, and we’re committed to supporting practical, environmentally responsible work that helps restore and protect South Africa’s dams and waterways — now and into the future.