Nicolas Salinas, Kim Weaver, Kelby English, Shirley Tebbutt and Julie Coetzee at the Delta Park dam. Photo: Mthulisi Lwazi Khuboni
Recently, members from the South African Institute for Aquatic Biodiversity (SAIAB) and the Centre for Biological Control (CBC) have embarked on a project to control the Water Hyacinth infestation in the dams at Delta Park together with Shirley Tebbutt.
These dedicated volunteers have employed nature’s own allies in the form of Megamelus Scutellaris (hoppers) to combat this invasive plant species. They released around 25 000 hoppers into the dams. The hoppers are expected to eat and kill the plants. They feed on the plants, by inserting a straw-like mouthpart that allows them to suck up the plant’s sap. In so doing, they also introduce plant diseases caused by fungi and bacteria. The plant gradually starts to die and stops producing flowers and daughter plants.
Megamelus scutellaris hoppers, also known as water hyacinth hoppers, are small insects native to South America. These remarkable creatures have proven to be effective biological control agents against water hyacinth infestations. By voraciously feeding on the leaves and stems of the invasive plant, they weaken its structure and impede its growth, ultimately reducing the density of the mats that choke waterways.
This approach has gained traction worldwide, and volunteers in Delta Park are now actively participating in efforts to rear and release Megamelus Scutellaris hoppers into affected areas. Their involvement signifies a grassroots commitment to preserving the ecological balance of Delta Park’s water bodies while also enhancing recreational opportunities for the community.
Here’s how Megamelus Scutellaris hoppers work in controlling water hyacinth:
1. Feeding Habits: These hoppers have a targeted appetite for water hyacinth, primarily consuming its leaves and stems. By causing damage to the plant, they weaken it and inhibit its growth over time.
2. Life Cycle: The life cycle of the hoppers is closely intertwined with that of water hyacinth. They lay their eggs on the plant’s leaves, and the nymphs develop and feed exclusively on the water hyacinth. This symbiotic relationship ensures sustained pressure on water hyacinth populations.
3. Environmental Compatibility: Using the hoppers as a biological control agent is environmentally friendly. Unlike chemical herbicides, this approach minimises ecological disruptions and preserves the balance of aquatic ecosystems.
4. Cost-Effectiveness: Once established, the hoppers provide a cost-effective long-term solution for water hyacinth management, requiring minimal ongoing intervention compared to chemical treatments.
The biological control does not aim to eradicate the invasive weed but to get the population to an acceptable level of control. If they can reduce the cover by 85-90%, they will consider this an excellent result. Unfortunately, manual removal can help to keep key areas of the dam clear but takes a lot of effort to do so. Chemical herbicides are also available for water hyacinth control, but their application requires a certified pest control officer to apply the herbicide. The hoppers are therefore an ideal solution. They pose no threat to the environment, and they cannot harm people or any other organism.
The hoppers that were released at the Delta Park dam. Photo: Mthulisi Lwazi Khuboni