This entails damaging or removing the plant by physical action. Different techniques could be used, e.g.
uprooting, felling, slashing, mowing, ringbarking or bark stripping. This
control option is only really feasible in sparse infestations or on small scale,
and for controlling species that do not coppice after cutting. Species that tend
to coppice, need to have the cut stumps or coppice growth treated with
herbicides following the mechanical treatment. Mechanical control is labour
intensive and therefore expensive, and could cause severe soil disturbance and
erosion. Read more about mechanical control in the ARC-PPRI publication
Rehabilitation recommendations after alien plant control by
Peta Campbell (order from Andrew
Mfolo). Contact Jeremy Goodall
for more information on mechanical control measures.
Chemical control involves the use of registered herbicides to
kill the target weed. ARC-PPRI's research on the chemical control of plant
invaders is aimed at developing safe, selective and affordable herbicide
treatments which will provide effective control in a wide range of environmental
conditions and which are compatible with biological control. The Division also
tests herbicides for registration purposes. Contact Jeremy Goodall for more information.
Biological weed control consists in the use of natural enemies
to reduce the vigour or reproductive potential of an invasive alien plant.
Research into the biological control of invasive alien plants is the main
activity of the Weeds Research Programme of ARC-PPRI.
Read more about the important role the Working for Water Programme plays in the biological control of invasive alien plants in South Africa.
To obtain biocontrol agents, the biocontrol implementation officers of the National Resource Management Programmes (NRMP) within the Department of Environment Affairs (DEA), previously known as the Working for Water Programme, can be contacted. Alternatively, contact the provincial representatives of the Directorate: Land Use and Soil Management (LUSM), Department of Agriculture, Forestry and Fisheries (DAFF).
The following documents can be downloaded:
A mycoherbicide is a formulation of fungal spores in a carrier,
which can be applied to weeds in the same way as a chemical herbicide. The
spores germinate on the plant, penetrate the plant tissues and cause a disease,
which could eventually kill the plant. Mycoherbicides are indigenous to the
country of use and therefore are already naturally present in the environment.
Under natural conditions they do not cause enough damage to the weed to have a
damaging impact. They are therefore mass produced and applied in an inundative
inoculation, using herbicide application equipment, which leads to an epidemic
of the disease knocking the weed population down. They can’t maintain the
epidemic under natural conditions, and need to be re-applied at regular
intervals. Because mycoherbicides are indigenous but only cause low levels of
disease under natural conditions, they do not pose a risk to non-target plants.
Considerable progress has been made in this field with the
development of a mycoherbicide from naturally occurring pathogens which is used
in the control of both hakea seedlings and mature plants (Hakatak). Research is
underway to develop a mycoherbicide against rooikrans. A number of fungi have
the potential to be developed as mycoherbicides against water hyacinth and
mesquite, and some research was done towards this goal in the past. An
innovative first for South Africa was the development of a non-pathogenic fungal
inoculant to prevent regrowth of stumps of black and golden wattle after felling
There are a number of important differences between
mycoherbicides and all the other biocontrol agents that have been introduced
against alien invasive weeds in South Africa (referred to as classical agents).
These are compared in the following table:
Frequently it is advisable to use a combination of two or more
of the control method mentioned above. This is known as integrated control.
Biological control can be integrated into conventional management plans with
great success, provided that the requirements of the biocontrol agents are kept
in mind, and provision is made for their continued survival in the affected
Information on ARC-PPRI's research into the control of various
invasive alien plants in South Africa is available on our website, by selecting
from a list of either botanical names or common names.
If you want to qualify yourself as a Pest Control Officer for
Environmental Weed Control, you could register for the course entitled Environmental Weed
Control, presented by Dr Graham Harding, using content supplied by ARC-PPRI.
(Contact e-mail: firstname.lastname@example.org)