Combating alien vegetation

Environmental management that includes alien vegetation control is vital to ensuring a sustainable water future in South Africa. In line with this, Bosch Munitech is currently combating the spread of water hyacinth in a KwaZulu-Natal river.

“South Africa is currently facing a major environmental problem, where invasive alien plants brought into the country, either intentionally or unintentionally, are aggressively spreading and taking precious water and space from our indigenous plants,” explains Zaheer Ismail, project manager: Environment, Bosch Munitech. “Many alien plants consume more water than local plants and are depleting our valuable underground water resources. Added to this, dense alien vegetation provides fuel for veld fires, causing damage to the soil structure beneath. Invasive alien plants are also a major threat to biodiversity in catchment areas, potentially disrupting the delicate natural balance in ecosystems. In South Africa, there are now approximately 383 invasive plant species that must be urgently controlled to prevent further damage.” In addressing this threat, Bosch Munitech is working closely with botanists and other environmental specialists, offering various services to assist with alien invasive plant management. “Together, we develop alien invasive species management plans for specific projects, including environmental management or fire risk settings. These management plans involve the identification of the types of species in the area and recommendations are provided as to which control and management methods are best suited for the eradication and management of alien vegetation,” says Ismail. Although alien invasive species can be managed in various ways, including manual and mechanical, biological (beetles and viruses) or chemical (herbicides) methods, Bosch Munitech opts for environmentally friendly manual, mechanical and biological methods. An example of this is an ongoing project on a river in Durban, KwaZulu-Natal, where Bosch Munitech is successfully controlling the spread of water hyacinth through a combination of manual and biological management methods. Manual control The manual removal of alien vegetation typically involves hand-pulling invasive plants, like water hyacinth, from the water surface, using a pitch fork and treble hooks. Because this method is labour-intensive, it is only effective for limited areas of infestation. Another problem with manual control is that vegetation removal from deep water, like canals, requires additional equipment such as rafts or boats, as well as various safety precautions.

In the current Durban river project, Bosch Munitech’s recommendation was to clear a pocket of water hyacinth from the river directly in front of the area where a specially designed and manufactured net was installed. Pitch forks and treble hooks were used to manually pull the hyacinth to the sides of the river. The plants were then moved to the stockpiling location, where they were left to dry before being transported to areas of rehabilitation, to be used as a mulch fertiliser.

Biological control Alien invasive plants like water hyacinth thrive and spread in an exponential manner, partly due to the lack of natural enemies, like browsers or pathogens, that exist in their native land.

Biological control agents, like insects, mites or other pathogens, can be introduced to remove an alien plant’s competitive advantage and to reduce its vigour to a level comparable to that of the natural vegetation. Biocontrol agents attack specific parts of target plants, such as leaves, stems or roots, or the reproductive parts, like flowers, fruits or seeds.

In Durban, Bosch Munitech is releasing control agents into the netted area of the river on a monthly basis and will continue to do so until the target population of control agents is achieved.

These biocontrol agents are received from the South African Sugar Research Institute, which has introduced a mass rearing programme for weed biocontrol agents.