- The Princess Vlei Forum has launched an experimental biocontrol project using Megamelus scutellaris planthoppers to manage the invasive water hyacinth by causing it to sink and die.
- The collaboration includes experts from the City of Cape Town, NGOs, and volunteers, working together to clear hyacinth and protect the aquatic ecosystem.
- The project, while still in its early stages, is showing promise, with 5,000 planthoppers already released in the Southfield canal and more consignments planned.
An experimental project to bring hyacinth, the world’s most invasive water weed under control at Princess Vlei, has seen the release of megamelus scutellaris (water hyacinth planthoppers) as a biocontrol agent.
Emma Oliver, secretary of the Princess Vlei Forum, explained how the “bugs” worked on controlling hyacinth.
“The megamelus scutellaris eats holes in the water hyacinth which causes it to sink and die,” she said. “The bugs are successful when there are millions of them.”
The “bugs” are being bred at Rhodes University and couriered to Cape Town.
“The bugs have been tried in Strandfontein but the water quality wasn’t good enough. However, it is successfully being used at the Hartebeespoort Dam.”
According to Oliver, tackling water hyacinth at Princess Vlei is an ongoing story of successes and failures.
“Each year the situation gets worse as a carpet of the pretty but destructive water hyacinth spreads rapidly across the vlei,” she said. “The dense growth suffocates life beneath it, prevents access to the water and disrupts the delicate balance in the vlei’s aquatic eco-systems.”
In August last year, the Zeekoevlei Catchment Forum was formed under the leadership of specialist fresh water ecologist Dr Liz Day, a collaboration which has enabled the creation of the Princess Vlei water hyacinth clearing team.
“The Catchment Forum brings together people from many diverse fields – the City of Cape Town, non-governmental organisations (NGOs), Friends Groups, volunteers – to find ways to improve the health of the catchment,” said Oliver. “The team members include City officials from Recreation and Parks, Storm water and River Management (CSRM) Invasive Species Unit which is breeding and introducing megamelus scutellaris or water hyacinth planthoppers.”
She added that the aim of the biocontrol is to get the planthoppers, in their millions, to eat the hyacinth – make holes in it, and cause it to sink and die.
Oliver explained, while several consignments will be needed, the first consignment of 5 000 bugs has already been released on hyacinth in the Southfield canal.
“The biocontrol work is new territory for many on the team, and needs to be carefully monitored,” she shared. “The success of the operation depends on good communication between the different players. For example, it is essential to ensure that heavy machinery contractors don’t remove the hyacinth where the bugs have been released.”
It is of utmost importance for all parties to work together in tackling the hyacinth at Princess Vlei.
“We have implemented various tactics to reduce the hyacinth, this includes ground boat crews who are tasked with removing the hyacinth from the waterbody.
“The City needs to remove the big heaps of water hycaninth that has been fully removed from the vlei. At the moment we are waiting for the City to do their part as teamwork is essential.”
Ward 72 councillor Kevin Southgate expressed his gratitude to the Princess Vlei Forum. “I want to express my sincere thanks to the Princess Vlei Forum for taking the initiative and for contributing towards removing the hyacinth from Princess Vlei,” he said.
Southgate added that the implementation of boat teams to assist with clearing hyacinth proved beneficial. “The Princess Vlei Forum has over time always expressed concern for the heavy duty equipment to remove the hyacinth and the damage it brings to the environment,” he said. “The deployment of the boat and the hand teams will really go a long way in protecting the environment and hopefully reduce the spread of the hyacinth. The project is truly an inspiration and will make a significant impact on the maintenance around the vlei in the months and years to come.”
