Biological Control Unit

Invasive plants have been brought into our country for various reasons including sources of food, e.g. prickly pears (Opuntia ficus-indica) and guava (Psidium guajava), as garden plants, e.g. cherry-pie (Lantana camara), as sand-stabilizers (e.g. the Acacia species) or they have been brought in accidently and then spread rapidly throughout our river and dam systems and irrigation canals.

The aquatic weeds choke up our waterways (see accompanying photographs), and cost South Africa millions of Rands each year to control, as they are difficult to eradicate. The water weeds impede recreational use of our freshwater systems, increase the loss of water from our storage systems and negatively affect the freshwater ecosystems when the weeds are in high densities.

The mechanical removal of water weeds is costly and time consuming, whereas biological control is a far more cost effective means of control. Biological control, using specific introduced insects, has proved to be the most successful control method for the majority of the water weeds. There are many success stories in South Africa, and the BCIAPRL has been part of this success. 

Professor Martin Hill sampling an infestation
of water hyacinth

A farm dam in Knysna that was covered in Kariba weed, Salvinia molesta, before and after the release of the biocontrol agent Cyrtobagous salviniae.