Since its launch in September 2014, the City of Cape Town’s Invasive Species Unit’s Insect Mass Rearing Facility in Westlake has been using an organic, cost-effective and environmentally safe biological control method to curb invasive plants by breeding and releasing their natural enemies: insects.
To date, the facility has reared more than 243 000 insects for release across the city to help root out alien invasive plants (AIP).
The facility currently rears agents for four aquatic AIPs, namely water hyacinth, parrot’s feather, kariba weed and water lettuce, which are considered the worst invasive weeds in South Africa. The facility also rears biocontrol agents for one terrestrial AIP, the prickly pear (Opuntia monocantha).
During his visit to the facility, Councillor Brett Herron, Mayoral Committee Member for Transport and Urban Development, saw first-hand how the insects are collected and packaged, ready for their next mission.
‘The visit to the insect-rearing facility has been most fascinating. In order to rear the agents, our team actually grows the plant which the agents are intended for. The aquatic invasive plants are grown in the artificial ponds at our facility and this is also where the agents grow and complete their life-cycle. The agents are then collected them from these ponds when they are ready to be released on their mission,’ said Councillor Herron.
Each of the insects are physically counted and then placed in plastic containers. Within hours they are transported and released on the specific invasive plant.
Generally, the insects are released every two weeks. The number of insects that are released depends on the size of the mission field. Successes in the field depends on the season and other activities that may be taking place in the area.
The Westlake river, which was previously choked with kariba weed, is an example of a mission accomplished.
Biological control is increasingly becoming a cost-effective method of control in the battle against infestations of invasive aquatic weeds and prickly pear.
In addition to the environmental benefits, the biocontrol project provides a platform for green job creation, skills development and education.