Biological control method gains traction in weed management – v
Precious Manomano
Herald Reporter
THE Ministry of Lands, Agriculture, Fisheries, Water and Rural Development has implemented biological control methods to combat invasive aquatic weeds in Chinyika Dam 2 in Goromonzi and Lake Chivero.
This innovative approach not only addresses the pressing issue of weed infestation, but also promotes environmental sustainability, highlighting the potential of natural solutions in managing ecological challenges.
Aquatic weeds, particularly Kariba weed (Salvinia molesta) and water hyacinth (Eichhornia crassipes), pose significant threats to the country’s water bodies.
These invasive species reduce available oxygen, obstruct recreational activities, clog irrigation systems, and degrade water quality.
They have emerged as a major concern for local communities that rely on these water sources for fishing, irrigation, and recreation.
A research officer under the Agricultural Research, Innovation and Specialist Services, Mr Nathan Sangombe, who is overseeing the biological control of invasive species, shared insights into the programme initiated in March 2023.
“We released a total of 1 400 Kariba weed weevils. The dam was 100 percent covered by the weed, so we developed a biocontrol programme and released these weevils gradually over four months,” he explained.
“This strategic release was designed to ensure that the weevils could easily access one another for mating, thereby increasing their population densities effectively.
“As the seasons changed, Sangombe noted that the population densities grew slowly due to lower temperatures.
“As we approached the warmer months of August and September, we began to see increases. By June 2024, we were getting approximately 2 000 weevils per square meter, leading to significant clearing of the weeds.
”The success of this biological control programme underscores the effectiveness of natural methods in managing invasive species.
“If people can witness how biological control works without chemicals, it shows the potential to restore aquatic ecosystems without harming the environment, humans, or livestock,” Mr Sangombe said.
“This approach not only helps in managing the weeds but also aligns with global sustainability goals, promoting a healthier ecosystem.”
Mr Sangombe urged all stakeholders to collaborate in the fight against invasive species.
“For biological control programmes to be successful, we need an integrated approach, with local communities taking ownership,” he said.
His call to action highlights the importance of collective effort in environmental stewardship.
A researcher from Rhodes University Dr Gerald Chikowore, from Rhodes University said weed infestations affect water quality because they thrive in nutrient-rich systems.
“The presence of these weeds indicates that the water is compromised,” he said.
He stressed that the impact of invasive species extended beyond aesthetics, affecting the entire aquatic ecosystem and the organisms that depend on it.
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