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PLAAGBEHEER/
PEST CONTROL
Ten main invasive plants
in South Africa
Invasive plants are a growing problem in South Africa. It would be easy to pass it off as the natural flow of
things – if these plants did not have such a major economic impact on farming operations. Over time they
have developed excellent survival strategies, rapidly take over large parts of farms, compete for light, water
and nutrients and are also expensive and difficult to control. The Department of Environmental Affairs has
released figures on the projected costs involved in controlling invasive plants (these costs exclude the control
of the Prosopis species). The lowest cost applies in North West, namely R0,9 billion, and the highest in the
Eastern Cape, namely R8 billion. Allegedly, 20 million hectares of land in South Africa have already been
taken over by invasive plants.
However, the top ten invasive plants mentioned here are not necessarily the biggest problem plants in
your area. Please contact the writer, Dr Franci Jordaan, for more information or for support in controlling
these plants.
Acacia longifolia (Andr.) Willd.
Golden wattle or long-leaved acacia is a small evergreen tree or patulous shrub that can grow 2 m to
8 m tall. This plant is indigenous to Australia and Tasmania. It grows in a variety of soils, but prefers well-
drained and moist soils. It often penetrates disturbed areas. It has a well-developed and strong root system.
These plants grow very rapidly and are known for their resistance to drought and diseases. The plant pro-
duces many seeds that are easily dispersed by ants and birds – in fact, it is the high seed production that
causes this plant to pose a major weed problem.
The negative aspects of the golden wattle include the following: It competes for light, space, water and
nutrients; it changes the landscape and habitat; because of the many seeds and rapid growth rate it dis-
places the indigenous vegetation; it changes the soil microbiota and soil chemical conditions; it can have
a negative effect on stream flow; it increases the risk of hot fires; the seed is a contaminant; it reduces the
biodiversity and grazing capacity if it occurs in dense stands.
Biological control agents occur on the plants and have a very effective control action – they should there-
fore always be the first choice for controlling this plant. Fire or mechanical control (cutting down the trees)
is not recommended, as the plants can sometimes sprout very quickly after such a disturbance. Various
chemicals are registered to control this plant and they can be useful in combination with mechanical con-
trol to get rid of it. According to the CARA Act the golden wattle is a category 1 plant – the landowner must
therefore control it.
Acacia longifolia